druid/docs/configuration/index.md

id	title
index	Configuration reference

This page documents all of the configuration properties for each Druid service type.

Recommended configuration file organization

A recommended way of organizing Druid configuration files can be seen in the conf directory in the Druid package root, shown below:

$ ls -R conf
druid

conf/druid:
_common       broker        coordinator   historical    middleManager overlord

conf/druid/_common:
common.runtime.properties log4j2.xml

conf/druid/broker:
jvm.config         runtime.properties

conf/druid/coordinator:
jvm.config         runtime.properties

conf/druid/historical:
jvm.config         runtime.properties

conf/druid/middleManager:
jvm.config         runtime.properties

conf/druid/overlord:
jvm.config         runtime.properties

Each directory has a runtime.properties file containing configuration properties for the specific Druid service corresponding to the directory, such as historical.

The jvm.config files contain JVM flags such as heap sizing properties for each service.

Common properties shared by all services are placed in _common/common.runtime.properties.

Configuration interpolation

Configuration values can be interpolated from System Properties, Environment Variables, or local files. Below is an example of how this can be used:

druid.metadata.storage.type=${env:METADATA_STORAGE_TYPE}
druid.processing.tmpDir=${sys:java.io.tmpdir}
druid.segmentCache.locations=${file:UTF-8:/config/segment-cache-def.json}

Interpolation is also recursive so you can do:

druid.segmentCache.locations=${file:UTF-8:${env:SEGMENT_DEF_LOCATION}}

If the property is not set, an exception will be thrown on startup, but a default can be provided if desired. Setting a default value will not work with file interpolation as an exception will be thrown if the file does not exist.

druid.metadata.storage.type=${env:METADATA_STORAGE_TYPE:-mysql}
druid.processing.tmpDir=${sys:java.io.tmpdir:-/tmp}

If you need to set a variable that is wrapped by ${...} but do not want it to be interpolated, you can escape it by adding another $. For example:

config.name=$${value}

Common configurations

The properties under this section are common configurations that should be shared across all Druid services in a cluster.

JVM configuration best practices

There are four JVM parameters that we set on all of our services:

• -Duser.timezone=UTC: This sets the default timezone of the JVM to UTC. We always set this and do not test with other default timezones, so local timezones might work, but they also might uncover weird and interesting bugs. To issue queries in a non-UTC timezone, see query granularities

• -Dfile.encoding=UTF-8 This is similar to timezone, we test assuming UTF-8. Local encodings might work, but they also might result in weird and interesting bugs.

• -Djava.io.tmpdir=<a path> Various parts of Druid use temporary files to interact with the file system. These files can become quite large. This means that systems that have small /tmp directories can cause problems for Druid. Therefore, set the JVM tmp directory to a location with ample space.

  Also consider the following when configuring the JVM tmp directory:

  • The temp directory should not be volatile tmpfs.
  • This directory should also have good read and write speed.
  • Avoid NFS mount.
  • The org.apache.druid.java.util.metrics.SysMonitor requires execute privileges on files in java.io.tmpdir. If you are using the system monitor, do not set java.io.tmpdir to noexec.

• -Djava.util.logging.manager=org.apache.logging.log4j.jul.LogManager This allows log4j2 to handle logs for non-log4j2 components (like jetty) which use standard java logging.

Extensions

Many of Druid's external dependencies can be plugged in as modules. Extensions can be provided using the following configs:

Property	Description	Default
druid.extensions.directory	The root extension directory where user can put extensions related files. Druid will load extensions stored under this directory.	extensions (This is a relative path to Druid's working directory)
druid.extensions.hadoopDependenciesDir	The root Hadoop dependencies directory where user can put Hadoop related dependencies files. Druid will load the dependencies based on the Hadoop coordinate specified in the Hadoop index task.	hadoop-dependencies (This is a relative path to Druid's working directory
druid.extensions.loadList	A JSON array of extensions to load from extension directories by Druid. If it is not specified, its value will be null and Druid will load all the extensions under druid.extensions.directory. If its value is empty list [], then no extensions will be loaded at all. It is also allowed to specify absolute path of other custom extensions not stored in the common extensions directory.	null
druid.extensions.searchCurrentClassloader	This is a boolean flag that determines if Druid will search the main classloader for extensions. It defaults to true but can be turned off if you have reason to not automatically add all modules on the classpath.	true
druid.extensions.useExtensionClassloaderFirst	This is a boolean flag that determines if Druid extensions should prefer loading classes from their own jars rather than jars bundled with Druid. If false, extensions must be compatible with classes provided by any jars bundled with Druid. If true, extensions may depend on conflicting versions.	false
druid.extensions.hadoopContainerDruidClasspath	Hadoop Indexing launches Hadoop jobs and this configuration provides way to explicitly set the user classpath for the Hadoop job. By default, this is computed automatically by Druid based on the Druid service classpath and set of extensions. However, sometimes you might want to be explicit to resolve dependency conflicts between Druid and Hadoop.	null
druid.extensions.addExtensionsToHadoopContainer	Only applicable if druid.extensions.hadoopContainerDruidClasspath is provided. If set to true, then extensions specified in the loadList are added to Hadoop container classpath. Note that when druid.extensions.hadoopContainerDruidClasspath is not provided then extensions are always added to Hadoop container classpath.	false

Modules

Property	Description	Default
druid.modules.excludeList	A JSON array of canonical class names (e.g., "org.apache.druid.somepackage.SomeModule") of module classes which shouldn't be loaded, even if they are found in extensions specified by druid.extensions.loadList, or in the list of core modules specified to be loaded on a particular Druid service type. Useful when some useful extension contains some module, which shouldn't be loaded on some Druid service type because some dependencies of that module couldn't be satisfied.	[]

ZooKeeper

We recommend just setting the base ZK path and the ZK service host, but all ZK paths that Druid uses can be overwritten to absolute paths.

Property	Description	Default
druid.zk.paths.base	Base ZooKeeper path.	/druid
druid.zk.service.host	The ZooKeeper hosts to connect to. This is a REQUIRED property and therefore a host address must be supplied.	none
druid.zk.service.user	The username to authenticate with ZooKeeper. This is an optional property.	none
druid.zk.service.pwd	The Password Provider or the string password to authenticate with ZooKeeper. This is an optional property.	none
druid.zk.service.authScheme	digest is the only authentication scheme supported.	digest

ZooKeeper behavior

Property	Description	Default
druid.zk.service.sessionTimeoutMs	ZooKeeper session timeout, in milliseconds.	30000
druid.zk.service.connectionTimeoutMs	ZooKeeper connection timeout, in milliseconds.	15000
druid.zk.service.compress	Boolean flag for whether or not created Znodes should be compressed.	true
druid.zk.service.acl	Boolean flag for whether or not to enable ACL security for ZooKeeper. If ACL is enabled, zNode creators will have all permissions.	false

Path configuration

Druid interacts with ZooKeeper through a set of standard path configurations. We recommend just setting the base ZooKeeper path, but all ZooKeeper paths that Druid uses can be overwritten to absolute paths.

Property	Description	Default
druid.zk.paths.base	Base ZooKeeper path.	/druid
druid.zk.paths.propertiesPath	ZooKeeper properties path.	${druid.zk.paths.base}/properties
druid.zk.paths.announcementsPath	Druid service announcement path.	${druid.zk.paths.base}/announcements
druid.zk.paths.liveSegmentsPath	Current path for where Druid services announce their segments.	${druid.zk.paths.base}/segments
druid.zk.paths.coordinatorPath	Used by the Coordinator for leader election.	${druid.zk.paths.base}/coordinator
druid.zk.paths.servedSegmentsPath	Deprecated. Legacy path for where Druid services announce their segments.	${druid.zk.paths.base}/servedSegments

The indexing service also uses its own set of paths. These configs can be included in the common configuration.

Property	Description	Default
druid.zk.paths.indexer.base	Base ZooKeeper path for	${druid.zk.paths.base}/indexer
druid.zk.paths.indexer.announcementsPath	MiddleManagers announce themselves here.	${druid.zk.paths.indexer.base}/announcements
druid.zk.paths.indexer.tasksPath	Used to assign tasks to MiddleManagers.	${druid.zk.paths.indexer.base}/tasks
druid.zk.paths.indexer.statusPath	Parent path for announcement of task statuses.	${druid.zk.paths.indexer.base}/status

If druid.zk.paths.base and druid.zk.paths.indexer.base are both set, and none of the other druid.zk.paths.* or druid.zk.paths.indexer.* values are set, then the other properties will be evaluated relative to their respective base. For example, if druid.zk.paths.base is set to /druid1 and druid.zk.paths.indexer.base is set to /druid2 then druid.zk.paths.announcementsPath will default to /druid1/announcements while druid.zk.paths.indexer.announcementsPath will default to /druid2/announcements.

The following path is used for service discovery. It is not affected by druid.zk.paths.base and must be specified separately.

Property	Description	Default
druid.discovery.curator.path	Services announce themselves under this ZooKeeper path.	/druid/discovery

TLS

General configuration

Property	Description	Default
druid.enablePlaintextPort	Enable/Disable HTTP connector.	true
druid.enableTlsPort	Enable/Disable HTTPS connector.	false

Although not recommended but both HTTP and HTTPS connectors can be enabled at a time and respective ports are configurable using druid.plaintextPort and druid.tlsPort properties on each service. Please see Configuration section of individual services to check the valid and default values for these ports.

Jetty server TLS configuration

Druid uses Jetty as an embedded web server. To learn more about TLS/SSL, certificates, and related concepts in Jetty, including explanations of the configuration settings below, see "Configuring SSL/TLS KeyStores" in the Jetty Operations Guide.

For information about TLS/SSL support in Java in general, see the Java Secure Socket Extension (JSSE) Reference Guide. The Java Cryptography Architecture Standard Algorithm Name Documentation for JDK 8 lists all possible values for the following properties, among others provided by the Java implementation.

Property	Description	Default	Required
druid.server.https.keyStorePath	The file path or URL of the TLS/SSL KeyStore.	none	yes
druid.server.https.keyStoreType	The type of the KeyStore.	none	yes
druid.server.https.certAlias	Alias of TLS/SSL certificate for the connector.	none	yes
druid.server.https.keyStorePassword	The Password Provider or String password for the KeyStore.	none	yes

Following table contains non-mandatory advanced configuration options, use caution.

Property	Description	Default	Required
druid.server.https.keyManagerFactoryAlgorithm	Algorithm to use for creating KeyManager, more details here.	javax.net.ssl.KeyManagerFactory.getDefaultAlgorithm()	no
druid.server.https.keyManagerPassword	The Password Provider or String password for the Key Manager.	none	no
druid.server.https.includeCipherSuites	List of cipher suite names to include. You can either use the exact cipher suite name or a regular expression.	Jetty's default include cipher list	no
druid.server.https.excludeCipherSuites	List of cipher suite names to exclude. You can either use the exact cipher suite name or a regular expression.	Jetty's default exclude cipher list	no
druid.server.https.includeProtocols	List of exact protocols names to include.	Jetty's default include protocol list	no
druid.server.https.excludeProtocols	List of exact protocols names to exclude.	Jetty's default exclude protocol list	no

Internal client TLS configuration (requires simple-client-sslcontext extension)

These properties apply to the SSLContext that will be provided to the internal HTTP client that Druid services use to communicate with each other. These properties require the simple-client-sslcontext extension to be loaded. Without it, Druid services will be unable to communicate with each other when TLS is enabled.

Property	Description	Default	Required
druid.client.https.protocol	SSL protocol to use.	TLSv1.2	no
druid.client.https.trustStoreType	The type of the key store where trusted root certificates are stored.	java.security.KeyStore.getDefaultType()	no
druid.client.https.trustStorePath	The file path or URL of the TLS/SSL Key store where trusted root certificates are stored.	none	yes
druid.client.https.trustStoreAlgorithm	Algorithm to be used by TrustManager to validate certificate chains	javax.net.ssl.TrustManagerFactory.getDefaultAlgorithm()	no
druid.client.https.trustStorePassword	The Password Provider or String password for the Trust Store.	none	yes

This document lists all the possible values for the above mentioned configs among others provided by Java implementation.

Authentication and authorization

Property	Type	Description	Default	Required
druid.auth.authenticatorChain	JSON List of Strings	List of Authenticator type names	["allowAll"]	no
druid.escalator.type	String	Type of the Escalator that should be used for internal Druid communications. This Escalator must use an authentication scheme that is supported by an Authenticator in druid.auth.authenticatorChain.	noop	no
druid.auth.authorizers	JSON List of Strings	List of Authorizer type names	["allowAll"]	no
druid.auth.unsecuredPaths	List of Strings	List of paths for which security checks will not be performed. All requests to these paths will be allowed.	[]	no
druid.auth.allowUnauthenticatedHttpOptions	Boolean	If true, skip authentication checks for HTTP OPTIONS requests. This is needed for certain use cases, such as supporting CORS pre-flight requests. Note that disabling authentication checks for OPTIONS requests will allow unauthenticated users to determine what Druid endpoints are valid (by checking if the OPTIONS request returns a 200 instead of 404), so enabling this option may reveal information about server configuration, including information about what extensions are loaded (if those extensions add endpoints).	false	no

For more information, please see Authentication and Authorization.

For configuration options for specific auth extensions, please refer to the extension documentation.

Startup logging

All services can log debugging information on startup.

Property	Description	Default
druid.startup.logging.logProperties	Log all properties on startup (from common.runtime.properties, runtime.properties, and the JVM command line).	false
druid.startup.logging.maskProperties	Masks sensitive properties (passwords, for example) containing theses words.	["password"]

Note that some sensitive information may be logged if these settings are enabled.

Request logging

All services that can serve queries can also log the query requests they see. Broker services can additionally log the SQL requests (both from HTTP and JDBC) they see. For an example of setting up request logging, see Request logging.

Property	Description	Default
druid.request.logging.type	How to log every query request. Choices: noop, file, emitter, slf4j, filtered, composing, switching	noop (request logging disabled by default)

To enable sending all the HTTP requests to a log, set org.apache.druid.jetty.RequestLog to the DEBUG level. See Logging for more information.

File request logging

The file request logger stores daily request logs on disk.

Property	Description	Default
druid.request.logging.dir	Historical, Realtime, and Broker services maintain request logs of all of the requests they get (interaction is via POST, so normal request logs don’t generally capture information about the actual query), this specifies the directory to store the request logs in	none
druid.request.logging.filePattern	Joda datetime format for each file	"yyyy-MM-dd'.log'"
druid.request.logging.durationToRetain	Period to retain the request logs on disk. The period should be at least longer than P1D.	none

The format of request logs is TSV, one line per requests, with five fields: timestamp, remote_addr, native_query, query_context, sql_query.

For native JSON request, the sql_query field is empty. For example:

2019-01-14T10:00:00.000Z        127.0.0.1   {"queryType":"topN","dataSource":{"type":"table","name":"wikiticker"},"virtualColumns":[],"dimension":{"type":"LegacyDimensionSpec","dimension":"page","outputName":"page","outputType":"STRING"},"metric":{"type":"LegacyTopNMetricSpec","metric":"count"},"threshold":10,"intervals":{"type":"LegacySegmentSpec","intervals":["2015-09-12T00:00:00.000Z/2015-09-13T00:00:00.000Z"]},"filter":null,"granularity":{"type":"all"},"aggregations":[{"type":"count","name":"count"}],"postAggregations":[],"context":{"queryId":"74c2d540-d700-4ebd-b4a9-3d02397976aa"},"descending":false}    {"query/time":100,"query/bytes":800,"success":true,"identity":"user1"}

For SQL query request, the native_query field is empty. For example:

2019-01-14T10:00:00.000Z        127.0.0.1       {"sqlQuery/time":100, "sqlQuery/planningTimeMs":10, "sqlQuery/bytes":600, "success":true, "identity":"user1"}  {"query":"SELECT page, COUNT(*) AS Edits FROM wikiticker WHERE TIME_IN_INTERVAL(\"__time\", '2015-09-12/2015-09-13') GROUP BY page ORDER BY Edits DESC LIMIT 10","context":{"sqlQueryId":"c9d035a0-5ffd-4a79-a865-3ffdadbb5fdd","nativeQueryIds":"[490978e4-f5c7-4cf6-b174-346e63cf8863]"}}

Emitter request logging

The emitter request logger emits every request to the external location specified in the emitter configuration.

Property	Description	Default
druid.request.logging.feed	Feed name for requests.	none

SLF4J request logging

The slf4j request logger logs every request using SLF4J. It serializes native queries into JSON in the log message regardless of the SLF4J format specification. Requests are logged under the class org.apache.druid.server.log.LoggingRequestLogger.

Property	Description	Default
druid.request.logging.setMDC	If you want to set MDC entries within the log entry, set this value to true. Your logging system must be configured to support MDC in order to format this data.	false
druid.request.logging.setContextMDC	Set to "true" to add the Druid query context to the MDC entries. Only applies when setMDC is true.	false

For a native query, the following MDC fields are populated when setMDC is true:

MDC field	Description
queryId	The query ID
sqlQueryId	The SQL query ID if this query is part of a SQL request
dataSource	The datasource the query was against
queryType	The type of the query
hasFilters	If the query has any filters
remoteAddr	The remote address of the requesting client
duration	The duration of the query interval
resultOrdering	The ordering of results
descending	If the query is a descending query

Filtered request logging

The filtered request logger filters requests based on the query type or how long a query takes to complete. For native queries, the logger only logs requests when the query/time metric exceeds the threshold provided in queryTimeThresholdMs. For SQL queries, it only logs requests when the sqlQuery/time metric exceeds threshold provided in sqlQueryTimeThresholdMs. See Metrics for more details on query metrics.

Requests that meet the threshold are logged using the request logger type set in druid.request.logging.delegate.type.

Property	Description	Default
druid.request.logging.queryTimeThresholdMs	Threshold value for the query/time metric in milliseconds.	0, i.e., no filtering
druid.request.logging.sqlQueryTimeThresholdMs	Threshold value for the sqlQuery/time metric in milliseconds.	0, i.e., no filtering
druid.request.logging.mutedQueryTypes	Query requests of these types are not logged. Query types are defined as string objects corresponding to the "queryType" value for the specified query in the Druid's native JSON query API. Misspelled query types will be ignored. Example to ignore scan and timeBoundary queries: ["scan", "timeBoundary"]	[]
druid.request.logging.delegate.type	Type of delegate request logger to log requests.	none

Composing request logging

The composing request logger emits request logs to multiple request loggers.

Property	Description	Default
druid.request.logging.loggerProviders	List of request loggers for emitting request logs.	none

Switching request logging

The switching request logger routes native query request logs to one request logger and SQL query request logs to another request logger.

Property	Description	Default
druid.request.logging.nativeQueryLogger	Request logger for emitting native query request logs.	none
druid.request.logging.sqlQueryLogger	Request logger for emitting SQL query request logs.	none

Audit logging

Coordinator and Overlord log changes to lookups, segment load/drop rules, and dynamic configuration changes for auditing.

Property	Description	Default
druid.audit.manager.auditHistoryMillis	Default duration for querying audit history.	1 week
druid.audit.manager.includePayloadAsDimensionInMetric	Boolean flag on whether to add payload column in service metric.	false
druid.audit.manager.maxPayloadSizeBytes	The maximum size of audit payload to store in Druid's metadata store audit table. If the size of audit payload exceeds this value, the audit log would be stored with a message indicating that the payload was omitted instead. Setting maxPayloadSizeBytes to -1 (default value) disables this check, meaning Druid will always store audit payload regardless of it's size. Setting to any negative number other than -1 is invalid. Human-readable format is supported, see here.	-1
druid.audit.manager.skipNullField	If true, the audit payload stored in metadata store will exclude any field with null value.	false

Enabling metrics

You can configure Druid services to emit metrics regularly from a number of monitors via emitters.

Property	Description	Default
druid.monitoring.emissionPeriod	Frequency that Druid emits metrics.	PT1M
druid.monitoring.monitors	Sets list of Druid monitors used by a service. Because individual monitors sometimes only work on specific process types, it is best to set this property for each process type individually in e.g. historical/runtime.properties rather than _common/common.runtime.properties.	none (no monitors)
druid.emitter	Setting this value initializes one of the emitter modules.	noop (metric emission disabled by default)

Metrics monitors

Metric monitoring is an essential part of Druid operations. The following monitors are available:

Name	Description
org.apache.druid.client.cache.CacheMonitor	Emits metrics (to logs) about the segment results cache for Historical and Broker services. Reports typical cache statistics include hits, misses, rates, and size (bytes and number of entries), as well as timeouts and and errors.
org.apache.druid.java.util.metrics.SysMonitor	Reports on various system activities and statuses using the SIGAR library. Requires execute privileges on files in java.io.tmpdir. Do not set java.io.tmpdir to noexec when using SysMonitor.
org.apache.druid.java.util.metrics.JvmMonitor	Reports various JVM-related statistics.
org.apache.druid.java.util.metrics.JvmCpuMonitor	Reports statistics of CPU consumption by the JVM.
org.apache.druid.java.util.metrics.CpuAcctDeltaMonitor	Reports consumed CPU as per the cpuacct cgroup.
org.apache.druid.java.util.metrics.JvmThreadsMonitor	Reports Thread statistics in the JVM, like numbers of total, daemon, started, died threads.
org.apache.druid.java.util.metrics.CgroupCpuMonitor	Reports CPU shares and quotas as per the cpu cgroup.
org.apache.druid.java.util.metrics.CgroupCpuSetMonitor	Reports CPU core/HT and memory node allocations as per the cpuset cgroup.
org.apache.druid.java.util.metrics.CgroupDiskMonitor	Reports disk statistic as per the blkio cgroup.
org.apache.druid.java.util.metrics.CgroupMemoryMonitor	Reports memory statistic as per the memory cgroup.
org.apache.druid.server.metrics.HistoricalMetricsMonitor	Reports statistics on Historical services. Available only on Historical services.
org.apache.druid.server.metrics.SegmentStatsMonitor	EXPERIMENTAL Reports statistics about segments on Historical services. Available only on Historical services. Not to be used when lazy loading is configured.
org.apache.druid.server.metrics.QueryCountStatsMonitor	Reports how many queries have been successful/failed/interrupted.
org.apache.druid.server.metrics.SubqueryCountStatsMonitor	Reports how many subqueries have been materialized as rows or bytes and various other statistics related to the subquery execution
org.apache.druid.server.emitter.HttpEmittingMonitor	Reports internal metrics of http or parametrized emitter (see below). Must not be used with another emitter type. See the description of the metrics here: https://github.com/apache/druid/pull/4973.
org.apache.druid.server.metrics.TaskCountStatsMonitor	Reports how many ingestion tasks are currently running/pending/waiting and also the number of successful/failed tasks per emission period.
org.apache.druid.server.metrics.TaskSlotCountStatsMonitor	Reports metrics about task slot usage per emission period.
org.apache.druid.server.metrics.WorkerTaskCountStatsMonitor	Reports how many ingestion tasks are currently running/pending/waiting, the number of successful/failed tasks, and metrics about task slot usage for the reporting worker, per emission period. Only supported by MiddleManager node types.
org.apache.druid.server.metrics.ServiceStatusMonitor	Reports a heartbeat for the service.

For example, you might configure monitors on all services for system and JVM information within common.runtime.properties as follows:

druid.monitoring.monitors=["org.apache.druid.java.util.metrics.SysMonitor","org.apache.druid.java.util.metrics.JvmMonitor"]

You can override cluster-wide configuration by amending the runtime.properties of individual services.

Metrics emitters

There are several emitters available:

• noop (default) disables metric emission.
• logging emits logs using Log4j2.
• http sends POST requests of JSON events.
• parametrized operates like the http emitter but fine-tunes the recipient URL based on the event feed.
• composing initializes multiple emitter modules.
• graphite emits metrics to a Graphite Carbon service.
• switching initializes and emits to multiple emitter modules based on the event feed.

Logging emitter module

The use this emitter module, set druid.emitter=logging. The logging emitter uses a Log4j2 logger named druid.emitter.logging.loggerClass to emit events. Each event is logged as a single json object with a Marker as the feed of the event. Users may wish to edit the log4j config to route these logs to different sources based on the feed of the event.

Property	Description	Default
druid.emitter.logging.loggerClass	The class used for logging.	org.apache.druid.java.util.emitter.core.LoggingEmitter
druid.emitter.logging.logLevel	Choices: debug, info, warn, error. The log level at which message are logged.	info

HTTP emitter module

Property	Description	Default
druid.emitter.http.flushMillis	How often the internal message buffer is flushed (data is sent).	60000
druid.emitter.http.flushCount	How many messages the internal message buffer can hold before flushing (sending).	500
druid.emitter.http.basicAuthentication	Password Provider for providing login and password for authentication in "login:password" form. For example, druid.emitter.http.basicAuthentication=admin:adminpassword uses Default Password Provider which allows plain text passwords.	not specified = no authentication
druid.emitter.http.flushTimeOut	The timeout after which an event should be sent to the endpoint, even if internal buffers are not filled, in milliseconds.	not specified = no timeout
druid.emitter.http.batchingStrategy	The strategy of how the batch is formatted. "ARRAY" means [event1,event2], "NEWLINES" means event1\nevent2, ONLY_EVENTS means event1event2.	ARRAY
druid.emitter.http.maxBatchSize	The maximum batch size, in bytes.	the minimum of (10% of JVM heap size divided by 2) or (5242880 (i. e. 5 MiB))
druid.emitter.http.batchQueueSizeLimit	The maximum number of batches in emitter queue, if there are problems with emitting.	the maximum of (2) or (10% of the JVM heap size divided by 5MiB)
druid.emitter.http.minHttpTimeoutMillis	If the speed of filling batches imposes timeout smaller than that, not even trying to send batch to endpoint, because it will likely fail, not being able to send the data that fast. Configure this depending based on emitter/successfulSending/minTimeMs metric. Reasonable values are 10ms..100ms.	0
druid.emitter.http.recipientBaseUrl	The base URL to emit messages to. Druid will POST JSON to be consumed at the HTTP endpoint specified by this property.	none, required config

HTTP emitter module TLS overrides

By default, when sending events to a TLS-enabled receiver, the HTTP Emitter uses an SSLContext obtained from the service described at Druid's internal communication over TLS, that is the same SSLContext that would be used for internal communications between Druid services.

In some use cases it may be desirable to have the HTTP Emitter use its own separate truststore configuration. For example, there may be organizational policies that prevent the TLS-enabled metrics receiver's certificate from being added to the same truststore used by Druid's internal HTTP client.

The following properties allow the HTTP Emitter to use its own truststore configuration when building its SSLContext.

Property	Description	Default
druid.emitter.http.ssl.useDefaultJavaContext	If set to true, the HttpEmitter will use SSLContext.getDefault(), the default Java SSLContext, and all other properties below are ignored.	false
druid.emitter.http.ssl.trustStorePath	The file path or URL of the TLS/SSL Key store where trusted root certificates are stored. If this is unspecified, the HTTP Emitter will use the same SSLContext as Druid's internal HTTP client, as described in the beginning of this section, and all other properties below are ignored.	null
druid.emitter.http.ssl.trustStoreType	The type of the key store where trusted root certificates are stored.	java.security.KeyStore.getDefaultType()
druid.emitter.http.ssl.trustStoreAlgorithm	Algorithm to be used by TrustManager to validate certificate chains	javax.net.ssl.TrustManagerFactory.getDefaultAlgorithm()
druid.emitter.http.ssl.trustStorePassword	The Password Provider or String password for the Trust Store.	none
druid.emitter.http.ssl.protocol	TLS protocol to use.	"TLSv1.2"

Parametrized HTTP emitter module

The parametrized emitter takes the same configs as the http emitter using the prefix druid.emitter.parametrized.httpEmitting.. For example:

• druid.emitter.parametrized.httpEmitting.flushMillis
• druid.emitter.parametrized.httpEmitting.flushCount
• druid.emitter.parametrized.httpEmitting.ssl.trustStorePath

Do not specify recipientBaseUrl with the parametrized emitter. Instead use recipientBaseUrlPattern described in the table below.

Property	Description	Default
druid.emitter.parametrized.recipientBaseUrlPattern	The URL pattern to send an event to, based on the event's feed. For example, http://foo.bar/{feed}, that will send event to http://foo.bar/metrics if the event's feed is "metrics".	none, required config

Composing emitter module

Property	Description	Default
druid.emitter.composing.emitters	List of emitter modules to load, such as ["logging","http"].	[]

Graphite emitter

To use graphite as emitter set druid.emitter=graphite. For configuration details, see Graphite emitter for the Graphite emitter Druid extension.

Switching emitter

To use switching as emitter set druid.emitter=switching.

Property	Description	Default
druid.emitter.switching.emitters	JSON map of feed to list of emitter modules that will be used for the mapped feed, such as {"metrics":["http"], "alerts":["logging"]}	{}
druid.emitter.switching.defaultEmitters	JSON list of emitter modules to load that will be used if there is no emitter specifically designated for that event's feed, such as ["logging","http"].	[]

Metadata storage

These properties specify the JDBC connection and other configuration around the metadata storage. The only services that connect to the metadata storage with these properties are the Coordinator and Overlord.

Property	Description	Default
druid.metadata.storage.type	The type of metadata storage to use. One of mysql, postgresql, or derby.	derby
druid.metadata.storage.connector.connectURI	The JDBC URI for the database to connect to	none
druid.metadata.storage.connector.user	The username to connect with.	none
druid.metadata.storage.connector.password	The Password Provider or String password used to connect with.	none
druid.metadata.storage.connector.createTables	If Druid requires a table and it doesn't exist, create it?	true
druid.metadata.storage.tables.base	The base name for tables.	druid
druid.metadata.storage.tables.dataSource	The table to use to look for datasources created by Kafka Indexing Service.	druid_dataSource
druid.metadata.storage.tables.pendingSegments	The table to use to look for pending segments.	druid_pendingSegments
druid.metadata.storage.tables.segments	The table to use to look for segments.	druid_segments
druid.metadata.storage.tables.rules	The table to use to look for segment load/drop rules.	druid_rules
druid.metadata.storage.tables.config	The table to use to look for configs.	druid_config
druid.metadata.storage.tables.tasks	Used by the indexing service to store tasks.	druid_tasks
druid.metadata.storage.tables.taskLog	Used by the indexing service to store task logs.	druid_tasklogs
druid.metadata.storage.tables.taskLock	Used by the indexing service to store task locks.	druid_tasklocks
druid.metadata.storage.tables.supervisors	Used by the indexing service to store supervisor configurations.	druid_supervisors
druid.metadata.storage.tables.audit	The table to use for audit history of configuration changes, such as Coordinator rules.	druid_audit

Deep storage

The configurations concern how to push and pull Segments from deep storage.

Property	Description	Default
druid.storage.type	The type of deep storage to use. One of local, noop, s3, hdfs, c*.	local

Local deep storage

Local deep storage uses the local filesystem.

Property	Description	Default
druid.storage.storageDirectory	Directory on disk to use as deep storage.	/tmp/druid/localStorage

Noop deep storage

This deep storage doesn't do anything. There are no configs.

S3 deep storage

This deep storage is used to interface with Amazon's S3. Note that the druid-s3-extensions extension must be loaded. The below table shows some important configurations for S3. See S3 Deep Storage for full configurations.

Property	Description	Default
druid.storage.bucket	S3 bucket name.	none
druid.storage.baseKey	S3 object key prefix for storage.	none
druid.storage.disableAcl	Boolean flag for ACL. If this is set to false, the full control would be granted to the bucket owner. This may require to set additional permissions. See S3 permissions settings.	false
druid.storage.archiveBucket	S3 bucket name for archiving when running the archive task.	none
druid.storage.archiveBaseKey	S3 object key prefix for archiving.	none
druid.storage.sse.type	Server-side encryption type. Should be one of s3, kms, and custom. See the below Server-side encryption section for more details.	None
druid.storage.sse.kms.keyId	AWS KMS key ID. This is used only when druid.storage.sse.type is kms and can be empty to use the default key ID.	None
druid.storage.sse.custom.base64EncodedKey	Base64-encoded key. Should be specified if druid.storage.sse.type is custom.	None
druid.storage.useS3aSchema	If true, use the "s3a" filesystem when using Hadoop-based ingestion. If false, the "s3n" filesystem will be used. Only affects Hadoop-based ingestion.	false

HDFS deep storage

This deep storage is used to interface with HDFS. You must load the druid-hdfs-storage extension.

Property	Description	Default
druid.storage.storageDirectory	HDFS directory to use as deep storage.	none

Cassandra deep storage

This deep storage is used to interface with Cassandra. You must load the druid-cassandra-storage extension.

Property	Description	Default
druid.storage.host	Cassandra host.	none
druid.storage.keyspace	Cassandra key space.	none

Centralized datasource schema

Centralized datasource schema is an experimental feature to centralized datasource schema building within the Coordinator. Traditionally, the datasource schema is built in the Brokers by combining schema for all the available segments of a datasource. Brokers issue segment metadata query to data nodes and tasks to fetch segment schema. In the new arrangement, tasks publish segment schema along with segment metadata to the database and schema for realtime segments is periodically pushed to the Coordinator in the segment announcement flow. This enables Coordinator to cache segment schemas and build datasource schema by combining segment schema. Brokers query the datasource schema from the Coordinator, while retaining the ability to build table schema if the need arises.

Property	Description	Default	Required
druid.centralizedDatasourceSchema.enabled	Boolean flag for enabling datasource schema building in the Coordinator, this should be specified in the common runtime properties.	false	No.
druid.indexer.fork.property.druid.centralizedDatasourceSchema.enabled	This config should be set when CentralizedDatasourceSchema feature is enabled. This should be specified in the MiddleManager runtime properties.	false	No.

For, stale schema cleanup configs, refer to properties with the prefix druid.coordinator.kill.segmentSchema in Metadata Management.

Ingestion security configuration

HDFS input source

You can set the following property to specify permissible protocols for the HDFS input source.

Property	Possible values	Description	Default
druid.ingestion.hdfs.allowedProtocols	List of protocols	Allowed protocols for the HDFS input source.	["hdfs"]

HTTP input source

You can set the following property to specify permissible protocols for the HTTP input source.

Property	Possible values	Description	Default
druid.ingestion.http.allowedProtocols	List of protocols	Allowed protocols for the HTTP input source.	["http", "https"]

External data access security configuration

JDBC connections to external databases

You can use the following properties to specify permissible JDBC options for:

• SQL input source
• globally cached JDBC lookups
• JDBC Data Fetcher for per-lookup caching.

These properties do not apply to metadata storage connections.

Property	Possible values	Description	Default
druid.access.jdbc.enforceAllowedProperties	Boolean	When true, Druid applies druid.access.jdbc.allowedProperties to JDBC connections starting with jdbc:postgresql:, jdbc:mysql:, or jdbc:mariadb:. When false, Druid allows any kind of JDBC connections without JDBC property validation. This config is for backward compatibility especially during upgrades since enforcing allow list can break existing ingestion jobs or lookups based on JDBC. This config is deprecated and will be removed in a future release.	true
druid.access.jdbc.allowedProperties	List of JDBC properties	Defines a list of allowed JDBC properties. Druid always enforces the list for all JDBC connections starting with jdbc:postgresql:, jdbc:mysql:, and jdbc:mariadb: if druid.access.jdbc.enforceAllowedProperties is set to true. This option is tested against MySQL connector 8.2.0, MariaDB connector 2.7.4, and PostgreSQL connector 42.2.14. Other connector versions might not work.	["useSSL", "requireSSL", "ssl", "sslmode"]
druid.access.jdbc.allowUnknownJdbcUrlFormat	Boolean	When false, Druid only accepts JDBC connections starting with jdbc:postgresql: or jdbc:mysql:. When true, Druid allows JDBC connections to any kind of database, but only enforces druid.access.jdbc.allowedProperties for PostgreSQL and MySQL/MariaDB.	true

Task logging

You can use the druid.indexer configuration to set a long-term storage location for task log files, and to set a retention policy.

For more information about ingestion tasks and the services of generating logs, see the task reference.

Log long-term storage

Property	Description	Default
druid.indexer.logs.type	Where to store task logs. noop, s3, azure, google, hdfs, file	file

File task logs

Store task logs in the local filesystem.

Property	Description	Default
druid.indexer.logs.directory	Local filesystem path.	log

S3 task logs

Store task logs in S3. Note that the druid-s3-extensions extension must be loaded.

Property	Description	Default
druid.indexer.logs.s3Bucket	S3 bucket name.	none
druid.indexer.logs.s3Prefix	S3 key prefix.	none
druid.indexer.logs.disableAcl	Boolean flag for ACL. If this is set to false, the full control would be granted to the bucket owner. If the task logs bucket is the same as the deep storage (S3) bucket, then the value of this property will need to be set to true if druid.storage.disableAcl has been set to true.	false

Azure Blob Store task logs

Store task logs in Azure Blob Store. To enable this feature, load the druid-azure-extensions extension, and configure deep storage for Azure. Druid uses the same authentication method configured for deep storage and stores task logs in the same storage account (set in druid.azure.account).

Property	Description	Default
druid.indexer.logs.container	The Azure Blob Store container to write logs to.	Must be set.
druid.indexer.logs.prefix	The path to prepend to logs.	Must be set.

Google Cloud Storage task logs

Store task logs in Google Cloud Storage.

Note: The druid-google-extensions extension must be loaded, and this uses the same storage settings as the deep storage module for google.

Property	Description	Default
druid.indexer.logs.bucket	The Google Cloud Storage bucket to write logs to	none
druid.indexer.logs.prefix	The path to prepend to logs	none

HDFS task logs

Store task logs in HDFS. Note that the druid-hdfs-storage extension must be loaded.

Property	Description	Default
druid.indexer.logs.directory	The directory to store logs.	none

Log retention policy

Property	Description	Default
druid.indexer.logs.kill.enabled	Boolean value for whether to enable deletion of old task logs. If set to true, Overlord will submit kill tasks periodically based on druid.indexer.logs.kill.delay specified, which will delete task logs from the log directory as well as tasks and tasklogs table entries in metadata storage except for tasks created in the last druid.indexer.logs.kill.durationToRetain period.	false
druid.indexer.logs.kill.durationToRetain	Required if kill is enabled. In milliseconds, task logs and entries in task-related metadata storage tables to be retained created in last x milliseconds.	None
druid.indexer.logs.kill.initialDelay	Optional. Number of milliseconds after Overlord start when first auto kill is run.	random value less than 300000 (5 mins)
druid.indexer.logs.kill.delay	Optional. Number of milliseconds of delay between successive executions of auto kill run.	21600000 (6 hours)

API error response

You can configure Druid API error responses to hide internal information like the Druid class name, stack trace, thread name, servlet name, code, line/column number, host, or IP address.

Property	Description	Default
druid.server.http.showDetailedJettyErrors	When set to true, any error from the Jetty layer / Jetty filter includes the following fields in the JSON response: servlet, message, url, status, and cause, if it exists. When set to false, the JSON response only includes message, url, and status. The field values remain unchanged.	true
druid.server.http.errorResponseTransform.strategy	Error response transform strategy. The strategy controls how Druid transforms error responses from Druid services. When unset or set to none, Druid leaves error responses unchanged.	none

Error response transform strategy

You can use an error response transform strategy to transform error responses from within Druid services to hide internal information. When you specify an error response transform strategy other than none, Druid transforms the error responses from Druid services as follows:

• For any query API that fails in the Router service, Druid sets the fields errorClass and host to null. Druid applies the transformation strategy to the errorMessage field.
• For any SQL query API that fails, for example POST /druid/v2/sql/..., Druid sets the fields errorClass and host to null. Druid applies the transformation strategy to the errorMessage field.
• For any JDBC related exceptions, Druid will turn all checked exceptions into QueryInterruptedException otherwise druid will attempt to keep the exception as the same type. For example if the original exception isn't owned by Druid it will become QueryInterruptedException. Druid applies the transformation strategy to the errorMessage field.

No error response transform strategy

In this mode, Druid leaves error responses from underlying services unchanged and returns the unchanged errors to the API client. This is the default Druid error response mode. To explicitly enable this strategy, set druid.server.http.errorResponseTransform.strategy to none.

Allowed regular expression error response transform strategy

In this mode, Druid validates the error responses from underlying services against a list of regular expressions. Only error messages that match a configured regular expression are returned. To enable this strategy, set druid.server.http.errorResponseTransform.strategy to allowedRegex.

Property	Description	Default
druid.server.http.errorResponseTransform.allowedRegex	The list of regular expressions Druid uses to validate error messages. If the error message matches any of the regular expressions, then Druid includes it in the response unchanged. If the error message does not match any of the regular expressions, Druid replaces the error message with null or with a default message depending on the type of underlying Exception.	[]

For example, consider the following error response:

{"error":"Plan validation failed","errorMessage":"org.apache.calcite.runtime.CalciteContextException: From line 1, column 15 to line 1, column 38: Object 'nonexistent-datasource' not found","errorClass":"org.apache.calcite.tools.ValidationException","host":null}

If druid.server.http.errorResponseTransform.allowedRegex is set to [], Druid transforms the query error response to the following:

{"error":"Plan validation failed","errorMessage":null,"errorClass":null,"host":null}

On the other hand, if druid.server.http.errorResponseTransform.allowedRegex is set to [".*CalciteContextException.*"] then Druid transforms the query error response to the following:

{"error":"Plan validation failed","errorMessage":"org.apache.calcite.runtime.CalciteContextException: From line 1, column 15 to line 1, column 38: Object 'nonexistent-datasource' not found","errorClass":null,"host":null}

Overlord discovery

This config is used to find the Overlord using Curator service discovery. Only required if you are actually running an Overlord.

Property	Description	Default
druid.selectors.indexing.serviceName	The druid.service name of the Overlord service. To start the Overlord with a different name, set it with this property.	druid/overlord

Coordinator discovery

This config is used to find the Coordinator using Curator service discovery. This config is used by the realtime indexing services to get information about the segments loaded in the cluster.

Property	Description	Default
druid.selectors.coordinator.serviceName	The druid.service name of the Coordinator service. To start the Coordinator with a different name, set it with this property.	druid/coordinator

Announcing segments

You can configure how to announce and unannounce Znodes in ZooKeeper (using Curator). For normal operations you do not need to override any of these configs.

Batch data segment announcer

In current Druid, multiple data segments may be announced under the same Znode.

Property	Description	Default
druid.announcer.segmentsPerNode	Each Znode contains info for up to this many segments.	50
druid.announcer.maxBytesPerNode	Max byte size for Znode. Allowed range is [1024, 1048576].	524288
druid.announcer.skipDimensionsAndMetrics	Skip Dimensions and Metrics list from segment announcements. NOTE: Enabling this will also remove the dimensions and metrics list from Coordinator and Broker endpoints.	false
druid.announcer.skipLoadSpec	Skip segment LoadSpec from segment announcements. NOTE: Enabling this will also remove the loadspec from Coordinator and Broker endpoints.	false

If you want to turn off the batch data segment announcer, you can add a property to skip announcing segments. You do not want to enable this config if you have any services using batch for druid.serverview.type

Property	Description	Default
druid.announcer.skipSegmentAnnouncementOnZk	Skip announcing segments to ZooKeeper. Note that the batch server view will not work if this is set to true.	false

JavaScript

Druid supports dynamic runtime extension through JavaScript functions. This functionality can be configured through the following properties.

Property	Description	Default
druid.javascript.enabled	Set to "true" to enable JavaScript functionality. This affects the JavaScript parser, filter, extractionFn, aggregator, post-aggregator, router strategy, and worker selection strategy.	false

:::info JavaScript-based functionality is disabled by default. Please refer to the Druid JavaScript programming guide for guidelines about using Druid's JavaScript functionality, including instructions on how to enable it. :::

Double column storage

Prior to version 0.13.0, Druid's storage layer used a 32-bit float representation to store columns created by the doubleSum, doubleMin, and doubleMax aggregators at indexing time. Starting from version 0.13.0 the default will be 64-bit floats for Double columns. Using 64-bit representation for double column will lead to avoid precision loss at the cost of doubling the storage size of such columns. To keep the old format set the system-wide property druid.indexing.doubleStorage=float. You can also use floatSum, floatMin, and floatMax to use 32-bit float representation. Support for 64-bit floating point columns was released in Druid 0.11.0, so if you use this feature then older versions of Druid will not be able to read your data segments.

Property	Description	Default
druid.indexing.doubleStorage	Set to "float" to use 32-bit double representation for double columns.	double

SQL compatible null handling

These configurations are deprecated and will be removed in a future release at which point Druid will always have SQl compatible null handling.

Prior to version 0.13.0, Druid string columns treated '' and null values as interchangeable, and numeric columns were unable to represent null values, coercing null to 0. Druid 0.13.0 introduced a mode which enabled SQL compatible null handling, allowing string columns to distinguish empty strings from nulls, and numeric columns to contain null rows.

Property	Description	Default
druid.generic.useDefaultValueForNull	Set to false to store and query data in SQL compatible mode. This configuration has been deprecated and will be removed in a future release, taking on the false behavior. When set to true (deprecated legacy mode), null values will be stored as '' for string columns and 0 for numeric columns.	false
druid.generic.useThreeValueLogicForNativeFilters	Set to true to use SQL compatible three-value logic when processing native Druid filters when druid.generic.useDefaultValueForNull=false and druid.expressions.useStrictBooleans=true. This configuration has been deprecated and will be removed in a future release, taking on the true behavior. When set to false Druid uses 2 value logic for filter processing, even when druid.generic.useDefaultValueForNull=false and druid.expressions.useStrictBooleans=true. See boolean handling for more details	true
druid.generic.ignoreNullsForStringCardinality	When set to true, null values will be ignored for the built-in cardinality aggregator over string columns. Set to false to include null values while estimating cardinality of only string columns using the built-in cardinality aggregator. This setting takes effect only when druid.generic.useDefaultValueForNull is set to true and is ignored in SQL compatibility mode. Additionally, empty strings (equivalent to null) are not counted when this is set to true. This configuration has been deprecated and will be removed in a future release since it has no effect when druid.generic.useDefaultValueForNull=false.	false

This mode does have a storage size and query performance cost, see segment documentation for more details.

HTTP client

All Druid components can communicate with each other over HTTP.

Property	Description	Default
druid.global.http.numConnections	Size of connection pool per destination URL. If there are more HTTP requests than this number that all need to speak to the same URL, then they will queue up.	20
druid.global.http.eagerInitialization	Indicates that http connections should be eagerly initialized. If set to true, numConnections connections are created upon initialization	false
druid.global.http.compressionCodec	Compression codec to communicate with others. May be "gzip" or "identity".	gzip
druid.global.http.readTimeout	The timeout for data reads.	PT15M
druid.global.http.unusedConnectionTimeout	The timeout for idle connections in connection pool. The connection in the pool will be closed after this timeout and a new one will be established. This timeout should be less than druid.global.http.readTimeout. Set this timeout = ~90% of druid.global.http.readTimeout	PT4M
druid.global.http.numMaxThreads	Maximum number of I/O worker threads	max(10, ((number of cores * 17) / 16 + 2) + 30)

Common endpoints configuration

This section contains the configuration options for endpoints that are supported by all services.

Property	Description	Default
druid.server.hiddenProperties	If property names or substring of property names (case insensitive) is in this list, responses of the /status/properties endpoint do not show these properties	["druid.s3.accessKey","druid.s3.secretKey","druid.metadata.storage.connector.password", "password", "key", "token", "pwd"]

Master server

This section contains the configuration options for the services that reside on Master servers (Coordinators and Overlords) in the suggested three-server configuration.

Coordinator

For general Coordinator services information, see Coordinator service.

Static Configuration

These Coordinator static configurations can be defined in the coordinator/runtime.properties file.

Coordinator service config

Property	Description	Default
druid.host	The host for the current service. This is used to advertise the current service location as reachable from another service and should generally be specified such that http://${druid.host}/ could actually talk to this service.	InetAddress.getLocalHost().getCanonicalHostName()
druid.bindOnHost	Indicating whether the service's internal jetty server bind on druid.host. Default is false, which means binding to all interfaces.	false
druid.plaintextPort	This is the port to actually listen on; unless port mapping is used, this will be the same port as is on druid.host	8081
druid.tlsPort	TLS port for HTTPS connector, if druid.enableTlsPort is set then this config will be used. If druid.host contains port then that port will be ignored. This should be a non-negative integer.	8281
druid.service	The name of the service. This is used as a dimension when emitting metrics and alerts to differentiate between the various services.	druid/coordinator

Coordinator operation

Property	Description	Default
druid.coordinator.period	The run period for the Coordinator. The Coordinator operates by maintaining the current state of the world in memory and periodically looking at the set of "used" segments and segments being served to make decisions about whether any changes need to be made to the data topology. This property sets the delay between each of these runs.	PT60S
druid.coordinator.period.indexingPeriod	How often to send compact/merge/conversion tasks to the indexing service. It's recommended to be longer than druid.manager.segments.pollDuration	PT1800S (30 mins)
druid.coordinator.startDelay	The operation of the Coordinator works on the assumption that it has an up-to-date view of the state of the world when it runs, the current ZooKeeper interaction code, however, is written in a way that doesn’t allow the Coordinator to know for a fact that it’s done loading the current state of the world. This delay is a hack to give it enough time to believe that it has all the data.	PT300S
druid.coordinator.load.timeout	The timeout duration for when the Coordinator assigns a segment to a Historical service.	PT15M
druid.coordinator.kill.pendingSegments.on	Boolean flag for whether or not the Coordinator clean up old entries in the pendingSegments table of metadata store. If set to true, Coordinator will check the created time of most recently complete task. If it doesn't exist, it finds the created time of the earliest running/pending/waiting tasks. Once the created time is found, then for all datasources not in the killPendingSegmentsSkipList (see Dynamic configuration), Coordinator will ask the Overlord to clean up the entries 1 day or more older than the found created time in the pendingSegments table. This will be done periodically based on druid.coordinator.period.indexingPeriod specified.	true
druid.coordinator.kill.on	Boolean flag for whether or not the Coordinator should submit kill task for unused segments, that is, permanently delete them from metadata store and deep storage. If set to true, then for all whitelisted datasources (or optionally all), Coordinator will submit tasks periodically based on period specified. A whitelist can be set via dynamic configuration killDataSourceWhitelist described later. When druid.coordinator.kill.on is true, segments are eligible for permanent deletion once their data intervals are older than druid.coordinator.kill.durationToRetain relative to the current time. If a segment's data interval is older than this threshold at the time it is marked unused, it is eligible for permanent deletion immediately after being marked unused.	false
druid.coordinator.kill.period	The frequency of sending kill tasks to the indexing service. The value must be greater than or equal to druid.coordinator.period.indexingPeriod. Only applies if kill is turned on.	Same as druid.coordinator.period.indexingPeriod
druid.coordinator.kill.durationToRetain	Only applies if you set druid.coordinator.kill.on to true. This value is ignored if druid.coordinator.kill.ignoreDurationToRetain is true. Valid configurations must be a ISO8601 period. Druid will not kill unused segments whose interval end date is beyond now - durationToRetain. durationToRetain can be a negative ISO8601 period, which would result in now - durationToRetain to be in the future. Note that the durationToRetain parameter applies to the segment interval, not the time that the segment was last marked unused. For example, if durationToRetain is set to P90D, then a segment for a time chunk 90 days in the past is eligible for permanent deletion immediately after being marked unused.	P90D
druid.coordinator.kill.ignoreDurationToRetain	A way to override druid.coordinator.kill.durationToRetain and tell the coordinator that you do not care about the end date of unused segment intervals when it comes to killing them. If true, the coordinator considers all unused segments as eligible to be killed.	false
druid.coordinator.kill.bufferPeriod	The amount of time that a segment must be unused before it is able to be permanently removed from metadata and deep storage. This can serve as a buffer period to prevent data loss if data ends up being needed after being marked unused.	P30D
druid.coordinator.kill.maxSegments	The number of unused segments to kill per kill task. This number must be greater than 0. This only applies when druid.coordinator.kill.on=true.	100
druid.coordinator.balancer.strategy	Specify the type of balancing strategy for the Coordinator to use to distribute segments among the Historical services. cachingCost is logically equivalent to cost but is more CPU-efficient on large clusters. diskNormalized weights the costs according to the servers' disk usage ratios - there are known issues with this strategy distributing segments unevenly across the cluster. random distributes segments among services randomly.	cost
druid.coordinator.balancer.cachingCost.awaitInitialization	Whether to wait for segment view initialization before creating the cachingCost balancing strategy. This property is enabled only when druid.coordinator.balancer.strategy is cachingCost. If set to true, the Coordinator will not start to assign segments, until the segment view is initialized. If set to false, the Coordinator will fallback to use the cost balancing strategy only if the segment view is not initialized yet. It may take much time to wait for the initialization since the cachingCost balancing strategy involves much computing to build itself.	false
druid.coordinator.loadqueuepeon.http.repeatDelay	The start and repeat delay (in milliseconds) for the load queue peon, which manages the load/drop queue of segments for any server.	1 minute
druid.coordinator.loadqueuepeon.http.batchSize	Number of segment load/drop requests to batch in one HTTP request. Note that it must be smaller than druid.segmentCache.numLoadingThreads config on Historical service.	1
druid.coordinator.asOverlord.enabled	Boolean value for whether this Coordinator service should act like an Overlord as well. This configuration allows users to simplify a Druid cluster by not having to deploy any standalone Overlord services. If set to true, then Overlord console is available at http://coordinator-host:port/console.html and be sure to set druid.coordinator.asOverlord.overlordService also.	false
druid.coordinator.asOverlord.overlordService	Required, if druid.coordinator.asOverlord.enabled is true. This must be same value as druid.service on standalone Overlord services and druid.selectors.indexing.serviceName on Middle Managers.	NULL

Metadata management

Property	Description	Required	Default
druid.coordinator.period.metadataStoreManagementPeriod	How often to run metadata management tasks in ISO 8601 duration format.	No	PT1H
druid.coordinator.kill.supervisor.on	Boolean value for whether to enable automatic deletion of terminated supervisors. If set to true, Coordinator will periodically remove terminated supervisors from the supervisor table in metadata storage.	No	true
druid.coordinator.kill.supervisor.period	How often to do automatic deletion of terminated supervisor in ISO 8601 duration format. Value must be equal to or greater than druid.coordinator.period.metadataStoreManagementPeriod. Only applies if druid.coordinator.kill.supervisor.on is set to true.	No	P1D
druid.coordinator.kill.supervisor.durationToRetain	Duration of terminated supervisor to be retained from created time in ISO 8601 duration format. Only applies if druid.coordinator.kill.supervisor.on is set to true.	Yes if druid.coordinator.kill.supervisor.on is set to true.	P90D
druid.coordinator.kill.audit.on	Boolean value for whether to enable automatic deletion of audit logs. If set to true, Coordinator will periodically remove audit logs from the audit table entries in metadata storage.	No	True
druid.coordinator.kill.audit.period	How often to do automatic deletion of audit logs in ISO 8601 duration format. Value must be equal to or greater than druid.coordinator.period.metadataStoreManagementPeriod. Only applies if druid.coordinator.kill.audit.on is set to true.	No	P1D
druid.coordinator.kill.audit.durationToRetain	Duration of audit logs to be retained from created time in ISO 8601 duration format. Only applies if druid.coordinator.kill.audit.on is set to true.	Yes if druid.coordinator.kill.audit.on is set to true.	P90D
druid.coordinator.kill.compaction.on	Boolean value for whether to enable automatic deletion of compaction configurations. If set to true, Coordinator will periodically remove compaction configuration of inactive datasource (datasource with no used and unused segments) from the config table in metadata storage.	No	False
druid.coordinator.kill.compaction.period	How often to do automatic deletion of compaction configurations in ISO 8601 duration format. Value must be equal to or greater than druid.coordinator.period.metadataStoreManagementPeriod. Only applies if druid.coordinator.kill.compaction.on is set to true.	No	P1D
druid.coordinator.kill.rule.on	Boolean value for whether to enable automatic deletion of rules. If set to true, Coordinator will periodically remove rules of inactive datasource (datasource with no used and unused segments) from the rule table in metadata storage.	No	True
druid.coordinator.kill.rule.period	How often to do automatic deletion of rules in ISO 8601 duration format. Value must be equal to or greater than druid.coordinator.period.metadataStoreManagementPeriod. Only applies if druid.coordinator.kill.rule.on is set to true.	No	P1D
druid.coordinator.kill.rule.durationToRetain	Duration of rules to be retained from created time in ISO 8601 duration format. Only applies if druid.coordinator.kill.rule.on is set to true.	Yes if druid.coordinator.kill.rule.on is set to true.	P90D
druid.coordinator.kill.datasource.on	Boolean value for whether to enable automatic deletion of datasource metadata (Note: datasource metadata only exists for datasource created from supervisor). If set to true, Coordinator will periodically remove datasource metadata of terminated supervisor from the datasource table in metadata storage.	No	True
druid.coordinator.kill.datasource.period	How often to do automatic deletion of datasource metadata in ISO 8601 duration format. Value must be equal to or greater than druid.coordinator.period.metadataStoreManagementPeriod. Only applies if druid.coordinator.kill.datasource.on is set to true.	No	P1D
druid.coordinator.kill.datasource.durationToRetain	Duration of datasource metadata to be retained from created time in ISO 8601 duration format. Only applies if druid.coordinator.kill.datasource.on is set to true.	Yes if druid.coordinator.kill.datasource.on is set to true.	P90D
druid.coordinator.kill.segmentSchema.on	Boolean value for whether to enable automatic deletion of unused segment schemas. If set to true, Coordinator will periodically identify segment schemas which are not referenced by any used segment and mark them as unused. At a later point, these unused schemas are deleted. Only applies if Centralized Datasource schema feature is enabled.	No	True
druid.coordinator.kill.segmentSchema.period	How often to do automatic deletion of segment schemas in ISO 8601 duration format. Value must be equal to or greater than druid.coordinator.period.metadataStoreManagementPeriod. Only applies if druid.coordinator.kill.segmentSchema.on is set to true.	No	P1D
druid.coordinator.kill.segmentSchema.durationToRetain	Duration of segment schemas to be retained from the time it was marked as unused in ISO 8601 duration format. Only applies if druid.coordinator.kill.segmentSchema.on is set to true.	Yes, if druid.coordinator.kill.segmentSchema.on is set to true.	P90D

Segment management

Property	Possible values	Description	Default
druid.serverview.type	batch or http	Segment discovery method to use. "http" enables discovering segments using HTTP instead of ZooKeeper.	http
druid.coordinator.segment.awaitInitializationOnStart	true or false	Whether the Coordinator will wait for its view of segments to fully initialize before starting up. If set to 'true', the Coordinator's HTTP server will not start up, and the Coordinator will not announce itself as available, until the server view is initialized.	true

Metadata retrieval

Property	Description	Default
druid.manager.config.pollDuration	How often the manager polls the config table for updates.	PT1M
druid.manager.segments.pollDuration	The duration between polls the Coordinator does for updates to the set of active segments. Generally defines the amount of lag time it can take for the Coordinator to notice new segments.	PT1M
druid.manager.rules.pollDuration	The duration between polls the Coordinator does for updates to the set of active rules. Generally defines the amount of lag time it can take for the Coordinator to notice rules.	PT1M
druid.manager.rules.defaultRule	The default rule for the cluster	_default
druid.manager.rules.alertThreshold	The duration after a failed poll upon which an alert should be emitted.	PT10M

Dynamic configuration

The Coordinator has dynamic configurations to tune certain behavior on the fly, without requiring a service restart. You can configure these parameters using the web console(recommended) or through the Coordinator dynamic configuration API.

The following table shows the dynamic configuration properties for the Coordinator.

Property	Description	Default
millisToWaitBeforeDeleting	How long does the Coordinator need to be a leader before it can start marking overshadowed segments as unused in metadata storage.	900000 (15 mins)
mergeBytesLimit	The maximum total uncompressed size in bytes of segments to merge.	524288000L
mergeSegmentsLimit	The maximum number of segments that can be in a single append task.	100
smartSegmentLoading	Enables "smart" segment loading mode which dynamically computes the optimal values of several properties that maximize Coordinator performance.	true
maxSegmentsToMove	The maximum number of segments that can be moved in a Historical tier at any given time.	100
replicantLifetime	The maximum number of Coordinator runs for which a segment can wait in the load queue of a Historical before Druid raises an alert.	15
replicationThrottleLimit	The maximum number of segment replicas that can be assigned to a historical tier in a single Coordinator run. This property prevents Historical services from becoming overwhelmed when loading extra replicas of segments that are already available in the cluster.	500
balancerComputeThreads	Thread pool size for computing moving cost of segments during segment balancing. Consider increasing this if you have a lot of segments and moving segments begins to stall.	num_cores / 2
killDataSourceWhitelist	List of specific data sources for which kill tasks are sent if property druid.coordinator.kill.on is true. This can be a list of comma-separated data source names or a JSON array.	none
killTaskSlotRatio	Ratio of total available task slots, including autoscaling if applicable that will be allowed for kill tasks. This value must be between 0 and 1. Only applicable for kill tasks that are spawned automatically by the coordinator's auto kill duty, which is enabled when druid.coordinator.kill.on is true.	0.1
maxKillTaskSlots	Maximum number of tasks that will be allowed for kill tasks. This limit only applies for kill tasks that are spawned automatically by the coordinator's auto kill duty, which is enabled when druid.coordinator.kill.on is true.	Integer.MAX_VALUE - no limit
killPendingSegmentsSkipList	List of data sources for which pendingSegments are NOT cleaned up if property druid.coordinator.kill.pendingSegments.on is true. This can be a list of comma-separated data sources or a JSON array.	none
maxSegmentsInNodeLoadingQueue	The maximum number of segments allowed in the load queue of any given server. Use this parameter to load segments faster if, for example, the cluster contains slow-loading nodes or if there are too many segments to be replicated to a particular node (when faster loading is preferred to better segments distribution). The optimal value depends on the loading speed of segments, acceptable replication time and number of nodes.	500
useRoundRobinSegmentAssignment	Boolean flag for whether segments should be assigned to Historical services in a round robin fashion. When disabled, segment assignment is done using the chosen balancer strategy. When enabled, this can speed up segment assignments leaving balancing to move the segments to their optimal locations (based on the balancer strategy) lazily.	true
decommissioningNodes	List of Historical servers to decommission. Coordinator will not assign new segments to decommissioning servers, and segments will be moved away from them to be placed on non-decommissioning servers at the maximum rate specified by maxSegmentsToMove.	none
pauseCoordination	Boolean flag for whether or not the Coordinator should execute its various duties of coordinating the cluster. Setting this to true essentially pauses all coordination work while allowing the API to remain up. Duties that are paused include all classes that implement the CoordinatorDuty interface. Such duties include: segment balancing, segment compaction, submitting kill tasks for unused segments (if enabled), logging of used segments in the cluster, marking of newly unused or overshadowed segments, matching and execution of load/drop rules for used segments, unloading segments that are no longer marked as used from Historical servers. An example of when an admin may want to pause coordination would be if they are doing deep storage maintenance on HDFS name nodes with downtime and don't want the Coordinator to be directing Historical nodes to hit the name node with API requests until maintenance is done and the deep store is declared healthy for use again.	false
replicateAfterLoadTimeout	Boolean flag for whether or not additional replication is needed for segments that have failed to load due to the expiry of druid.coordinator.load.timeout. If this is set to true, the Coordinator will attempt to replicate the failed segment on a different historical server. This helps improve the segment availability if there are a few slow Historicals in the cluster. However, the slow Historical may still load the segment later and the Coordinator may issue drop requests if the segment is over-replicated.	false

Smart segment loading

The smartSegmentLoading mode simplifies Coordinator configuration for segment loading and balancing. If you enable this mode, do not provide values for the properties in the table below as the Coordinator computes them automatically. Druid computes the values to optimize Coordinator performance, based on the current state of the cluster.

If you enable smartSegmentLoading mode, Druid ignores any value you provide for the following properties.

Property	Computed value	Description
useRoundRobinSegmentAssignment	true	Speeds up segment assignment.
maxSegmentsInNodeLoadingQueue	0	Removes the limit on load queue size.
replicationThrottleLimit	5% of used segments, minimum value 100	Prevents aggressive replication when a Historical disappears only intermittently.
replicantLifetime	60	Allows segments to wait about an hour (assuming a Coordinator period of 1 minute) in the load queue before an alert is raised. In smartSegmentLoading mode, load queues are not limited by size. Segments might therefore assigned to a load queue even if the corresponding server is slow to load them.
maxSegmentsToMove	2% of used segments, minimum value 100, maximum value 1000	Ensures that some segments are always moving in the cluster to keep it well balanced. The maximum value keeps the Coordinator run times bounded.
balancerComputeThreads	num_cores / 2	Ensures that there are enough threads to perform balancing computations without hogging all Coordinator resources.

When smartSegmentLoading is disabled, Druid uses the configured values of these properties. Disable smartSegmentLoading only if you want to explicitly set the values of any of the above properties.

Lookups dynamic configuration

These configuration options control Coordinator lookup management. For configurations that affect lookup propagation, see Dynamic configuration for lookups.

Property	Description	Default
druid.manager.lookups.hostDeleteTimeout	How long to wait for a DELETE request to a particular service before considering the DELETE a failure.	PT1S
druid.manager.lookups.hostUpdateTimeout	How long to wait for a POST request to a particular service before considering the POST a failure.	PT10S
druid.manager.lookups.deleteAllTimeout	How long to wait for all DELETE requests to finish before considering the delete attempt a failure.	PT10S
druid.manager.lookups.updateAllTimeout	How long to wait for all POST requests to finish before considering the attempt a failure.	PT60S
druid.manager.lookups.threadPoolSize	How many services can be managed concurrently (concurrent POST and DELETE requests). Requests this limit will wait in a queue until a slot becomes available.	10
druid.manager.lookups.period	Number of milliseconds between checks for configuration changes.	120000 (2 minutes)

Automatic compaction dynamic configuration

You can set or update automatic compaction properties dynamically using the Automatic compaction API without restarting Coordinators.

For details about segment compaction, see Segment size optimization.

You can configure automatic compaction through the following properties:

Property	Description	Required
dataSource	The datasource name to be compacted.	yes
taskPriority	Priority of compaction task.	no (default = 25)
inputSegmentSizeBytes	Maximum number of total segment bytes processed per compaction task. Since a time chunk must be processed in its entirety, if the segments for a particular time chunk have a total size in bytes greater than this parameter, compaction will not run for that time chunk.	no (default = 100,000,000,000,000 i.e. 100TB)
skipOffsetFromLatest	The offset for searching segments to be compacted in ISO 8601 duration format. Strongly recommended to set for realtime datasources. See Data handling with compaction.	no (default = "P1D")
tuningConfig	Tuning config for compaction tasks. See below Automatic compaction tuningConfig.	no
taskContext	Task context for compaction tasks.	no
granularitySpec	Custom granularitySpec. See Automatic compaction granularitySpec.	no
dimensionsSpec	Custom dimensionsSpec. See Automatic compaction dimensionsSpec.	no
transformSpec	Custom transformSpec. See Automatic compaction transformSpec.	no
metricsSpec	Custom metricsSpec. The compaction task preserves any existing metrics regardless of whether metricsSpec is specified. If metricsSpec is specified, Druid does not reapply any aggregators matching the metric names specified in metricsSpec to rows that already have the associated metrics. For rows that do not already have the metric specified in metricsSpec, Druid applies the metric aggregator on the source column, then proceeds to combine the metrics across segments as usual. If metricsSpec is not specified, Druid automatically discovers the metrics in the existing segments and combines existing metrics with the same metric name across segments. Aggregators for metrics with the same name are assumed to be compatible for combining across segments, otherwise the compaction task may fail.	no
ioConfig	IO config for compaction tasks. See Automatic compaction ioConfig.	no

Automatic compaction config example:

{
  "dataSource": "wikiticker",
  "granularitySpec" : {
    "segmentGranularity" : "none"
  }
}

Compaction tasks fail when higher priority tasks cause Druid to revoke their locks. By default, realtime tasks like ingestion have a higher priority than compaction tasks. Frequent conflicts between compaction tasks and realtime tasks can cause the Coordinator's automatic compaction to hang. You may see this issue with streaming ingestion from Kafka and Kinesis, which ingest late-arriving data.

To mitigate this problem, set skipOffsetFromLatest to a value large enough so that arriving data tends to fall outside the offset value from the current time. This way you can avoid conflicts between compaction tasks and realtime ingestion tasks. For example, if you want to skip over segments from thirty days prior to the end time of the most recent segment, assign "skipOffsetFromLatest": "P30D". For more information, see Avoid conflicts with ingestion.

Automatic compaction tuningConfig

Auto-compaction supports a subset of the tuningConfig for Parallel task.

The following table shows the supported configurations for auto-compaction.

Property	Description	Required
type	The task type, this should always be index_parallel.	yes
maxRowsInMemory	Used in determining when intermediate persists to disk should occur. Normally user does not need to set this, but depending on the nature of data, if rows are short in terms of bytes, user may not want to store a million rows in memory and this value should be set.	no (default = 1000000)
maxBytesInMemory	Used in determining when intermediate persists to disk should occur. Normally this is computed internally and user does not need to set it. This value represents number of bytes to aggregate in heap memory before persisting. This is based on a rough estimate of memory usage and not actual usage. The maximum heap memory usage for indexing is maxBytesInMemory * (2 + maxPendingPersists)	no (default = 1/6 of max JVM memory)
splitHintSpec	Used to give a hint to control the amount of data that each first phase task reads. This hint could be ignored depending on the implementation of the input source. See Split hint spec for more details.	no (default = size-based split hint spec)
partitionsSpec	Defines how to partition data in each time chunk, see PartitionsSpec	no (default = dynamic)
indexSpec	Defines segment storage format options to be used at indexing time, see IndexSpec	no
indexSpecForIntermediatePersists	Defines segment storage format options to be used at indexing time for intermediate persisted temporary segments. this can be used to disable dimension/metric compression on intermediate segments to reduce memory required for final merging. however, disabling compression on intermediate segments might increase page cache use while they are used before getting merged into final segment published, see IndexSpec for possible values.	no
maxPendingPersists	Maximum number of persists that can be pending but not started. If this limit would be exceeded by a new intermediate persist, ingestion will block until the currently-running persist finishes. Maximum heap memory usage for indexing scales with maxRowsInMemory * (2 + maxPendingPersists).	no (default = 0, meaning one persist can be running concurrently with ingestion, and none can be queued up)
pushTimeout	Milliseconds to wait for pushing segments. It must be >= 0, where 0 means to wait forever.	no (default = 0)
segmentWriteOutMediumFactory	Segment write-out medium to use when creating segments. See SegmentWriteOutMediumFactory.	no (default is the value from druid.peon.defaultSegmentWriteOutMediumFactory.type is used)
maxNumConcurrentSubTasks	Maximum number of worker tasks which can be run in parallel at the same time. The supervisor task would spawn worker tasks up to maxNumConcurrentSubTasks regardless of the current available task slots. If this value is set to 1, the Supervisor task processes data ingestion on its own instead of spawning worker tasks. If this value is set to too large, too many worker tasks can be created which might block other ingestion. Check Capacity Planning for more details.	no (default = 1)
maxRetry	Maximum number of retries on task failures.	no (default = 3)
maxNumSegmentsToMerge	Max limit for the number of segments that a single task can merge at the same time in the second phase. Used only with hashed or single_dim partitionsSpec.	no (default = 100)
totalNumMergeTasks	Total number of tasks to merge segments in the merge phase when partitionsSpec is set to hashed or single_dim.	no (default = 10)
taskStatusCheckPeriodMs	Polling period in milliseconds to check running task statuses.	no (default = 1000)
chatHandlerTimeout	Timeout for reporting the pushed segments in worker tasks.	no (default = PT10S)
chatHandlerNumRetries	Retries for reporting the pushed segments in worker tasks.	no (default = 5)

Automatic compaction granularitySpec

Field	Description	Required
segmentGranularity	Time chunking period for the segment granularity. Defaults to 'null', which preserves the original segment granularity. Accepts all Query granularity values.	No
queryGranularity	The resolution of timestamp storage within each segment. Defaults to 'null', which preserves the original query granularity. Accepts all Query granularity values.	No
rollup	Whether to enable ingestion-time rollup or not. Defaults to null, which preserves the original setting. Note that once data is rollup, individual records can no longer be recovered.	No

Automatic compaction dimensionsSpec

Field	Description	Required
dimensions	A list of dimension names or objects. Defaults to null, which preserves the original dimensions. Note that setting this will cause segments manually compacted with dimensionExclusions to be compacted again.	No

Automatic compaction transformSpec

Field	Description	Required
filter	Conditionally filters input rows during compaction. Only rows that pass the filter will be included in the compacted segments. Any of Druid's standard query filters can be used. Defaults to null, which will not filter any row.	No

Automatic compaction ioConfig

Auto-compaction supports a subset of the ioConfig for Parallel task. The below is a list of the supported configurations for auto-compaction.

Property	Description	Default	Required
dropExisting	If true the compaction task replaces all existing segments fully contained by the umbrella interval of the compacted segments when the task publishes new segments and tombstones. If compaction fails, Druid does not publish any segments or tombstones. WARNING: this functionality is still in beta. Note that changing this config does not cause intervals to be compacted again.	false	no

Overlord

For general Overlord service information, see Overlord.

Overlord static configuration

These Overlord static configurations can be defined in the overlord/runtime.properties file.

Overlord service configs

Property	Description	Default
druid.host	The host for the current service. This is used to advertise the current service location as reachable from another service and should generally be specified such that http://${druid.host}/ could actually talk to this service.	InetAddress.getLocalHost().getCanonicalHostName()
druid.bindOnHost	Indicating whether the service's internal jetty server bind on druid.host. Default is false, which means binding to all interfaces.	false
druid.plaintextPort	This is the port to actually listen on; unless port mapping is used, this will be the same port as is on druid.host.	8090
druid.tlsPort	TLS port for HTTPS connector, if druid.enableTlsPort is set then this config will be used. If druid.host contains port then that port will be ignored. This should be a non-negative Integer.	8290
druid.service	The name of the service. This is used as a dimension when emitting metrics and alerts to differentiate between the various services.	druid/overlord

Overlord operations

Property	Description	Default
druid.indexer.runner.type	Indicates whether tasks should be run locally using local or in a distributed environment using remote. The recommended option is httpRemote, which is similar to remote but uses HTTP to interact with Middle Managers instead of ZooKeeper.	httpRemote
druid.indexer.storage.type	Indicates whether incoming tasks should be stored locally (in heap) or in metadata storage. One of local or metadata. local is mainly for internal testing while metadata is recommended in production because storing incoming tasks in metadata storage allows for tasks to be resumed if the Overlord should fail.	local
druid.indexer.storage.recentlyFinishedThreshold	Duration of time to store task results. Default is 24 hours. If you have hundreds of tasks running in a day, consider increasing this threshold.	PT24H
druid.indexer.tasklock.forceTimeChunkLock	Setting this to false is still experimental If set, all tasks are enforced to use time chunk lock. If not set, each task automatically chooses a lock type to use. This configuration can be overwritten by setting forceTimeChunkLock in the task context. See Task Locking & Priority for more details about locking in tasks.	true
druid.indexer.tasklock.batchSegmentAllocation	If set to true, Druid performs segment allocate actions in batches to improve throughput and reduce the average task/action/run/time. See batching segmentAllocate actions for details.	true
druid.indexer.tasklock.batchAllocationWaitTime	Number of milliseconds after Druid adds the first segment allocate action to a batch, until it executes the batch. Allows the batch to add more requests and improve the average segment allocation run time. This configuration takes effect only if batchSegmentAllocation is enabled.	0
druid.indexer.task.default.context	Default task context that is applied to all tasks submitted to the Overlord. Any default in this config does not override neither the context values the user provides nor druid.indexer.tasklock.forceTimeChunkLock.	empty context
druid.indexer.queue.maxSize	Maximum number of active tasks at one time.	Integer.MAX_VALUE
druid.indexer.queue.startDelay	Sleep this long before starting Overlord queue management. This can be useful to give a cluster time to re-orient itself (for example, after a widespread network issue).	PT1M
druid.indexer.queue.restartDelay	Sleep this long when Overlord queue management throws an exception before trying again.	PT30S
druid.indexer.queue.storageSyncRate	Sync Overlord state this often with an underlying task persistence mechanism.	PT1M
druid.indexer.queue.maxTaskPayloadSize	Maximum allowed size in bytes of a single task payload accepted by the Overlord.	none (allow all task payload sizes)

The following configs only apply if the Overlord is running in remote mode. For a description of local vs. remote mode, see Overlord service.

Property	Description	Default
druid.indexer.runner.taskAssignmentTimeout	How long to wait after a task has been assigned to a MiddleManager before throwing an error.	PT5M
druid.indexer.runner.minWorkerVersion	The minimum MiddleManager version to send tasks to. The version number is a string. This affects the expected behavior during certain operations like comparison against druid.worker.version. Specifically, the version comparison follows dictionary order. Use ISO8601 date format for the version to accommodate date comparisons.	"0"
druid.indexer.runner.parallelIndexTaskSlotRatio	The ratio of task slots available for parallel indexing supervisor tasks per worker. The specified value must be in the range [0, 1].	1
druid.indexer.runner.compressZnodes	Indicates whether or not the Overlord should expect MiddleManagers to compress Znodes.	true
druid.indexer.runner.maxZnodeBytes	The maximum size Znode in bytes that can be created in ZooKeeper, should be in the range of [10KiB, 2GiB). Human-readable format is supported.	512 KiB
druid.indexer.runner.taskCleanupTimeout	How long to wait before failing a task after a MiddleManager is disconnected from ZooKeeper.	PT15M
druid.indexer.runner.taskShutdownLinkTimeout	How long to wait on a shutdown request to a MiddleManager before timing out	PT1M
druid.indexer.runner.pendingTasksRunnerNumThreads	Number of threads to allocate pending-tasks to workers, must be at least 1.	1
druid.indexer.runner.maxRetriesBeforeBlacklist	Number of consecutive times the MiddleManager can fail tasks, before the worker is blacklisted, must be at least 1	5
druid.indexer.runner.workerBlackListBackoffTime	How long to wait before a task is whitelisted again. This value should be greater that the value set for taskBlackListCleanupPeriod.	PT15M
druid.indexer.runner.workerBlackListCleanupPeriod	A duration after which the cleanup thread will startup to clean blacklisted workers.	PT5M
druid.indexer.runner.maxPercentageBlacklistWorkers	The maximum percentage of workers to blacklist, this must be between 0 and 100.	20

If autoscaling is enabled, you can set these additional configs:

Property	Description	Default
druid.indexer.autoscale.strategy	Sets the strategy to run when autoscaling is required. One of noop, ec2 or gce.	noop
druid.indexer.autoscale.doAutoscale	If set to true, autoscaling will be enabled.	false
druid.indexer.autoscale.provisionPeriod	How often to check whether or not new MiddleManagers should be added.	PT1M
druid.indexer.autoscale.terminatePeriod	How often to check when MiddleManagers should be removed.	PT5M
druid.indexer.autoscale.originTime	The starting reference timestamp that the terminate period increments upon.	2012-01-01T00:55:00.000Z
druid.indexer.autoscale.workerIdleTimeout	How long can a worker be idle (not a run task) before it can be considered for termination.	PT90M
druid.indexer.autoscale.maxScalingDuration	How long the Overlord will wait around for a MiddleManager to show up before giving up.	PT15M
druid.indexer.autoscale.numEventsToTrack	The number of autoscaling related events (node creation and termination) to track.	10
druid.indexer.autoscale.pendingTaskTimeout	How long a task can be in "pending" state before the Overlord tries to scale up.	PT30S
druid.indexer.autoscale.workerVersion	If set, will only create nodes of set version during autoscaling. Overrides dynamic configuration.	null
druid.indexer.autoscale.workerPort	The port that MiddleManagers will run on.	8080
druid.indexer.autoscale.workerCapacityHint	An estimation of the number of task slots available for each worker launched by the auto scaler when there are no workers running. The auto scaler uses the worker capacity hint to launch workers with an adequate capacity to handle pending tasks. When unset or set to a value less than or equal to 0, the auto scaler scales workers equal to the value for minNumWorkers in autoScaler config instead. The auto scaler assumes that each worker, either a MiddleManager or indexer, has the same amount of task slots. Therefore, when all your workers have the same capacity (homogeneous capacity), set the value for autoscale.workerCapacityHint equal to druid.worker.capacity. If your workers have different capacities (heterogeneous capacity), set the value to the average of druid.worker.capacity across the workers. For example, if two workers have druid.worker.capacity=10, and one has druid.worker.capacity=4, set autoscale.workerCapacityHint=8. Only applies to pendingTaskBased provisioning strategy.	-1

Supervisors

Property	Description	Default
druid.supervisor.healthinessThreshold	The number of successful runs before an unhealthy supervisor is again considered healthy.	3
druid.supervisor.unhealthinessThreshold	The number of failed runs before the supervisor is considered unhealthy.	3
druid.supervisor.taskHealthinessThreshold	The number of consecutive task successes before an unhealthy supervisor is again considered healthy.	3
druid.supervisor.taskUnhealthinessThreshold	The number of consecutive task failures before the supervisor is considered unhealthy.	3
druid.supervisor.storeStackTrace	Whether full stack traces of supervisor exceptions should be stored and returned by the supervisor /status endpoint.	false
druid.supervisor.maxStoredExceptionEvents	The maximum number of exception events that can be returned through the supervisor /status endpoint.	max(healthinessThreshold, unhealthinessThreshold)
druid.supervisor.idleConfig.enabled	If true, supervisor can become idle if there is no data on input stream/topic for some time.	false
druid.supervisor.idleConfig.inactiveAfterMillis	Supervisor is marked as idle if all existing data has been read from input topic and no new data has been published for inactiveAfterMillis milliseconds.	600_000

The druid.supervisor.idleConfig.* specification in the Overlord runtime properties defines the default behavior for the entire cluster. See Idle Configuration in Kafka Supervisor IOConfig to override it for an individual supervisor.

Overlord dynamic configuration

The Overlord has dynamic configurations to tune how Druid assigns tasks to workers. You can configure these parameters using the web console or through the Overlord dynamic configuration API.

The following table shows the dynamic configuration properties for the Overlord.

Property	Description	Default
selectStrategy	Describes how to assign tasks to MiddleManagers. The type can be equalDistribution, equalDistributionWithCategorySpec, fillCapacity, fillCapacityWithCategorySpec, and javascript.	{"type":"equalDistribution"}
autoScaler	Only used if autoscaling is enabled.	null

The following is an example of an Overlord dynamic config:

Click to view the example

{
  "selectStrategy": {
    "type": "fillCapacity",
    "affinityConfig": {
      "affinity": {
        "datasource1": ["host1:port", "host2:port"],
        "datasource2": ["host3:port"]
      }
    }
  },
  "autoScaler": {
    "type": "ec2",
    "minNumWorkers": 2,
    "maxNumWorkers": 12,
    "envConfig": {
      "availabilityZone": "us-east-1a",
      "nodeData": {
        "amiId": "${AMI}",
        "instanceType": "c3.8xlarge",
        "minInstances": 1,
        "maxInstances": 1,
        "securityGroupIds": ["${IDs}"],
        "keyName": "${KEY_NAME}"
      },
      "userData": {
        "impl": "string",
        "data": "${SCRIPT_COMMAND}",
        "versionReplacementString": ":VERSION:",
        "version": null
      }
    }
  }
}

Worker select strategy

The select strategy controls how Druid assigns tasks to workers (MiddleManagers). At a high level, the select strategy determines the list of eligible workers for a given task using either an affinityConfig or a categorySpec. Then, Druid assigns the task by either trying to distribute load equally (equalDistribution) or to fill as many workers as possible to capacity (fillCapacity). There are 4 options for select strategies:

• equalDistribution
• equalDistributionWithCategorySpec
• fillCapacity
• fillCapacityWithCategorySpec

A javascript option is also available but should only be used for prototyping new strategies.

If an affinityConfig is provided (as part of fillCapacity and equalDistribution strategies) for a given task, the list of workers eligible to be assigned is determined as follows:

• a non-affinity worker if no affinity is specified for that datasource. Any worker not listed in the affinityConfig is considered a non-affinity worker.
• a non-affinity worker if preferred workers are not available and the affinity is weak i.e. strong: false.
• a preferred worker listed in the affinityConfig for this datasource if it has available capacity
• no worker if preferred workers are not available and affinity is strong i.e. strong: true. In this case, the task remains in "pending" state. The chosen provisioning strategy (e.g. pendingTaskBased) may then use the total number of pending tasks to determine if a new node should be provisioned.

Note that every worker listed in the affinityConfig will only be used for the assigned datasources and no other.

If a categorySpec is provided (as part of fillCapacityWithCategorySpec and equalDistributionWithCategorySpec strategies), then a task of a given datasource may be assigned to:

• any worker if no category config is given for task type
• any worker if category config is given for task type but no category is given for datasource and there's no default category
• a preferred worker (based on category config and category for datasource) if available
• any worker if category config and category are given but no preferred worker is available and category config is weak
• not assigned at all if preferred workers are not available and category config is strong

In both the cases, Druid determines the list of eligible workers and selects one depending on their load with the goal of either distributing the load equally or filling as few workers as possible.

If you are using auto-scaling, use the fillCapacity select strategy since auto-scaled nodes can not be assigned a category, and you want the work to be concentrated on the fewest number of workers to allow the empty ones to scale down.

equalDistribution

Tasks are assigned to the MiddleManager with the most free slots at the time the task begins running. This evenly distributes work across your MiddleManagers.

Property	Description	Default
type	equalDistribution	required; must be equalDistribution
affinityConfig	AffinityConfig object	null (no affinity)

equalDistributionWithCategorySpec

This strategy is a variant of equalDistribution, which supports workerCategorySpec field rather than affinityConfig. By specifying workerCategorySpec, you can assign tasks to run on different categories of MiddleManagers based on the type and dataSource of the task. This strategy doesn't work with AutoScaler since the behavior is undefined.

Property	Description	Default
type	equalDistributionWithCategorySpec	required; must be equalDistributionWithCategorySpec
workerCategorySpec	WorkerCategorySpec object	null (no worker category spec)

The following example shows tasks of type index_kafka that default to running on MiddleManagers of category c1, except for tasks that write to datasource ds1, which run on MiddleManagers of category c2.

{
  "selectStrategy": {
    "type": "equalDistributionWithCategorySpec",
    "workerCategorySpec": {
      "strong": false,
      "categoryMap": {
        "index_kafka": {
          "defaultCategory": "c1",
          "categoryAffinity": {
            "ds1": "c2"
          }
        }
      }
    }
  }
}

fillCapacity

Tasks are assigned to the worker with the most currently-running tasks. This is useful when you are auto-scaling MiddleManagers since it tends to pack some full and leave others empty. The empty ones can be safely terminated.

Note that if druid.indexer.runner.pendingTasksRunnerNumThreads is set to N > 1, then this strategy will fill N MiddleManagers up to capacity simultaneously, rather than a single MiddleManager.

Property	Description	Default
type	fillCapacity	required; must be fillCapacity
affinityConfig	AffinityConfig object	null (no affinity)

fillCapacityWithCategorySpec

This strategy is a variant of fillCapacity, which supports workerCategorySpec instead of an affinityConfig. The usage is the same as equalDistributionWithCategorySpec strategy. This strategy doesn't work with AutoScaler since the behavior is undefined.

Property	Description	Default
type	fillCapacityWithCategorySpec.	required; must be fillCapacityWithCategorySpec
workerCategorySpec	WorkerCategorySpec object	null (no worker category spec)

javascript

Allows defining arbitrary logic for selecting workers to run task using a JavaScript function. The function is passed remoteTaskRunnerConfig, map of workerId to available workers and task to be executed and returns the workerId on which the task should be run or null if the task cannot be run. It can be used for rapid development of missing features where the worker selection logic is to be changed or tuned often. If the selection logic is quite complex and cannot be easily tested in JavaScript environment, its better to write a druid extension module with extending current worker selection strategies written in java.

Property	Description	Default
type	javascript	required; must be javascript
function	String representing JavaScript function

The following example shows a function that sends batch_index_task to workers 10.0.0.1 and 10.0.0.2 and all other tasks to other available workers.

{
  "type":"javascript",
  "function":"function (config, zkWorkers, task) {\nvar batch_workers = new java.util.ArrayList();\nbatch_workers.add(\"middleManager1_hostname:8091\");\nbatch_workers.add(\"middleManager2_hostname:8091\");\nworkers = zkWorkers.keySet().toArray();\nvar sortedWorkers = new Array()\n;for(var i = 0; i < workers.length; i++){\n sortedWorkers[i] = workers[i];\n}\nArray.prototype.sort.call(sortedWorkers,function(a, b){return zkWorkers.get(b).getCurrCapacityUsed() - zkWorkers.get(a).getCurrCapacityUsed();});\nvar minWorkerVer = config.getMinWorkerVersion();\nfor (var i = 0; i < sortedWorkers.length; i++) {\n var worker = sortedWorkers[i];\n  var zkWorker = zkWorkers.get(worker);\n  if(zkWorker.canRunTask(task) && zkWorker.isValidVersion(minWorkerVer)){\n    if(task.getType() == 'index_hadoop' && batch_workers.contains(worker)){\n      return worker;\n    } else {\n      if(task.getType() != 'index_hadoop' && !batch_workers.contains(worker)){\n        return worker;\n      }\n    }\n  }\n}\nreturn null;\n}"
}

:::info JavaScript-based functionality is disabled by default. Refer to the Druid JavaScript programming guide for guidelines about using Druid's JavaScript functionality, including instructions on how to enable it. :::

affinityConfig

Use the affinityConfig field to pass affinity configuration to the equalDistribution and fillCapacity strategies. If not provided, the default is to have no affinity.

Property	Description	Default
affinity	JSON object mapping a datasource String name to a list of indexing service MiddleManager host:port values. Druid doesn't perform DNS resolution, so the 'host' value must match what is configured on the MiddleManager and what the MiddleManager announces itself as (examine the Overlord logs to see what your MiddleManager announces itself as).	{}
strong	When true tasks for a datasource must be assigned to affinity-mapped MiddleManagers. Tasks remain queued until a slot becomes available. When false, Druid may assign tasks for a datasource to other MiddleManagers when affinity-mapped MiddleManagers are unavailable to run queued tasks.	false

workerCategorySpec

You can provide workerCategorySpec to the equalDistributionWithCategorySpec and fillCapacityWithCategorySpec strategies using the workerCategorySpec field. If not provided, the default is to not use it at all.

Property	Description	Default
categoryMap	A JSON map object mapping a task type String name to a CategoryConfig object, by which you can specify category config for different task type.	{}
strong	With weak workerCategorySpec (the default), tasks for a dataSource may be assigned to other MiddleManagers if the MiddleManagers specified in categoryMap are not able to run all pending tasks in the queue for that dataSource. With strong workerCategorySpec, tasks for a dataSource will only ever be assigned to their specified MiddleManagers, and will wait in the pending queue if necessary.	false

CategoryConfig

Property	Description	Default
defaultCategory	Specify default category for a task type.	null
categoryAffinity	A JSON map object mapping a datasource String name to a category String name of the MiddleManager. If category isn't specified for a datasource, then using the defaultCategory. If no specified category and the defaultCategory is also null, then tasks can run on any available MiddleManagers.	null

Autoscaler

Amazon's EC2 together with Google's GCE are currently the only supported autoscalers.

EC2's autoscaler properties are:

Property	Description	Default
type	ec2	0
minNumWorkers	The minimum number of workers that can be in the cluster at any given time.	0
maxNumWorkers	The maximum number of workers that can be in the cluster at any given time.	0
envConfig.availabilityZone	What Amazon availability zone to run in.	none
envConfig.nodeData	A JSON object that describes how to launch new nodes.	none; required
envConfig.userData	A JSON object that describes how to configure new nodes. If you have set druid.indexer.autoscale.workerVersion, this must have a versionReplacementString. Otherwise, a versionReplacementString is not necessary.	none; optional

For GCE's properties, please refer to the gce-extensions.

Data server

This section contains the configuration options for the services that reside on Data servers (MiddleManagers/Peons and Historicals) in the suggested three-server configuration.

Configuration options for the Indexer process are also provided here.

MiddleManager and Peons

These MiddleManager and Peon configurations can be defined in the middleManager/runtime.properties file.

MiddleManager service config

Property	Description	Default
druid.host	The host for the current service. This is used to advertise the current service location as reachable from another service and should generally be specified such that http://${druid.host}/ could actually talk to this service	InetAddress.getLocalHost().getCanonicalHostName()
druid.bindOnHost	Indicating whether the service's internal jetty server bind on druid.host. Default is false, which means binding to all interfaces.	false
druid.plaintextPort	This is the port to actually listen on; unless port mapping is used, this will be the same port as is on druid.host	8091
druid.tlsPort	TLS port for HTTPS connector, if druid.enableTlsPort is set then this config will be used. If druid.host contains port then that port will be ignored. This should be a non-negative Integer.	8291
druid.service	The name of the service. This is used as a dimension when emitting metrics and alerts to differentiate between the various services	druid/middlemanager

MiddleManager configuration

MiddleManagers pass their configurations down to their child peons. The MiddleManager requires the following configs:

Property	Description	Default
druid.indexer.runner.allowedPrefixes	Whitelist of prefixes for configs that can be passed down to child peons.	com.metamx, druid, org.apache.druid, user.timezone, file.encoding, java.io.tmpdir, hadoop
druid.indexer.runner.compressZnodes	Indicates whether or not the MiddleManagers should compress Znodes.	true
druid.indexer.runner.classpath	Java classpath for the peon.	System.getProperty("java.class.path")
druid.indexer.runner.javaCommand	Command required to execute java.	java
druid.indexer.runner.javaOpts	DEPRECATED A string of -X Java options to pass to the peon's JVM. Quotable parameters or parameters with spaces are encouraged to use javaOptsArray	''
druid.indexer.runner.javaOptsArray	A JSON array of strings to be passed in as options to the peon's JVM. This is additive to druid.indexer.runner.javaOpts and is recommended for properly handling arguments which contain quotes or spaces like ["-XX:OnOutOfMemoryError=kill -9 %p"]	[]
druid.indexer.runner.maxZnodeBytes	The maximum size Znode in bytes that can be created in ZooKeeper, should be in the range of [10KiB, 2GiB). Human-readable format is supported.	512KiB
druid.indexer.runner.startPort	Starting port used for Peon services, should be greater than 1023 and less than 65536.	8100
druid.indexer.runner.endPort	Ending port used for Peon services, should be greater than or equal to druid.indexer.runner.startPort and less than 65536.	65535
druid.indexer.runner.ports	A JSON array of integers to specify ports that used for Peon services. If provided and non-empty, ports for Peon services will be chosen from these ports. And druid.indexer.runner.startPort/druid.indexer.runner.endPort will be completely ignored.	[]
druid.worker.ip	The IP of the worker.	localhost
druid.worker.version	Version identifier for the MiddleManager. The version number is a string. This affects the expected behavior during certain operations like comparison against druid.indexer.runner.minWorkerVersion. Specifically, the version comparison follows dictionary order. Use ISO8601 date format for the version to accommodate date comparisons.	0
druid.worker.capacity	Maximum number of tasks the MiddleManager can accept.	Number of CPUs on the machine - 1
druid.worker.baseTaskDirs	List of base temporary working directories, one of which is assigned per task in a round-robin fashion. This property can be used to allow usage of multiple disks for indexing. This property is recommended in place of and takes precedence over ${druid.indexer.task.baseTaskDir}. If this configuration is not set, ${druid.indexer.task.baseTaskDir} is used. For example, druid.worker.baseTaskDirs=[\"PATH1\",\"PATH2\",...].	null
druid.worker.baseTaskDirSize	The total amount of bytes that can be used by tasks on any single task dir. This value is treated symmetrically across all directories, that is, if this is 500 GB and there are 3 baseTaskDirs, then each of those task directories is assumed to allow for 500 GB to be used and a total of 1.5 TB will potentially be available across all tasks. The actual amount of memory assigned to each task is discussed in Configuring task storage sizes	Long.MAX_VALUE
druid.worker.category	A string to name the category that the MiddleManager node belongs to.	_default_worker_category
druid.indexer.fork.property.druid.centralizedDatasourceSchema.enabled	This config should be set when Centralized Datasource Schema feature is enabled.	false

Peon processing

Processing properties set on the MiddleManager are passed through to Peons.

Property	Description	Default
druid.processing.buffer.sizeBytes	This specifies a buffer size (less than 2GiB) for the storage of intermediate results. The computation engine in both the Historical and Realtime processes will use a scratch buffer of this size to do all of their intermediate computations off-heap. Larger values allow for more aggregations in a single pass over the data while smaller values can require more passes depending on the query that is being executed. Human-readable format is supported.	auto (max 1 GiB)
druid.processing.buffer.poolCacheMaxCount	Processing buffer pool caches the buffers for later use. This is the maximum count that the cache will grow to. Note that pool can create more buffers than it can cache if necessary.	Integer.MAX_VALUE
druid.processing.formatString	Realtime and Historical processes use this format string to name their processing threads.	processing-%s
druid.processing.numMergeBuffers	The number of direct memory buffers available for merging query results. The buffers are sized by druid.processing.buffer.sizeBytes. This property is effectively a concurrency limit for queries that require merging buffers. If you are using any queries that require merge buffers (currently, just groupBy) then you should have at least two of these.	max(2, druid.processing.numThreads / 4)
druid.processing.numThreads	The number of processing threads to have available for parallel processing of segments. Our rule of thumb is num_cores - 1, which means that even under heavy load there will still be one core available to do background tasks like talking with ZooKeeper and pulling down segments. If only one core is available, this property defaults to the value 1.	Number of cores - 1 (or 1)
druid.processing.fifo	Enables the processing queue to treat tasks of equal priority in a FIFO manner.	true
druid.processing.tmpDir	Path where temporary files created while processing a query should be stored. If specified, this configuration takes priority over the default java.io.tmpdir path.	path represented by java.io.tmpdir
druid.processing.intermediaryData.storage.type	Storage type for intermediary segments of data shuffle between native parallel index tasks. Set to local to store segment files in the local storage of the MiddleManager or Indexer. Set to deepstore to use configured deep storage for better fault tolerance during rolling updates. When the storage type is deepstore, Druid stores the data in the shuffle-data directory under the configured deep storage path. Druid does not support automated cleanup for the shuffle-data directory. You can set up cloud storage lifecycle rules for automated cleanup of data at the shuffle-data prefix location.	local

The amount of direct memory needed by Druid is at least druid.processing.buffer.sizeBytes * (druid.processing.numMergeBuffers + druid.processing.numThreads + 1). You can ensure at least this amount of direct memory is available by providing -XX:MaxDirectMemorySize=<VALUE> in druid.indexer.runner.javaOptsArray as documented above.

Peon query configuration

See general query configuration.

Peon caching

You can optionally configure caching to be enabled on the peons by setting caching configs here.

Property	Possible Values	Description	Default
druid.realtime.cache.useCache	true, false	Enable the cache on the realtime.	false
druid.realtime.cache.populateCache	true, false	Populate the cache on the realtime.	false
druid.realtime.cache.unCacheable	All druid query types	All query types to not cache.	[]
druid.realtime.cache.maxEntrySize	positive integer	Maximum cache entry size in bytes.	1_000_000

See cache configuration for how to configure cache settings.

Additional Peon configuration

Although Peons inherit the configurations of their parent MiddleManagers, explicit child Peon configs in MiddleManager can be set by prefixing them with:

druid.indexer.fork.property

Additional Peon configs include:

Property	Description	Default
druid.peon.mode	One of local or remote. Setting this property to local means you intend to run the Peon as a standalone process which is not recommended.	remote
druid.indexer.task.baseDir	Base temporary working directory.	System.getProperty("java.io.tmpdir")
druid.indexer.task.baseTaskDir	Base temporary working directory for tasks.	${druid.indexer.task.baseDir}/persistent/task
druid.indexer.task.defaultHadoopCoordinates	Hadoop version to use with HadoopIndexTasks that do not request a particular version.	org.apache.hadoop:hadoop-client-api:3.3.6, org.apache.hadoop:hadoop-client-runtime:3.3.6
druid.indexer.task.defaultRowFlushBoundary	Highest row count before persisting to disk. Used for indexing generating tasks.	75000
druid.indexer.task.directoryLockTimeout	Wait this long for zombie Peons to exit before giving up on their replacements.	PT10M
druid.indexer.task.gracefulShutdownTimeout	Wait this long on MiddleManager restart for restorable tasks to gracefully exit.	PT5M
druid.indexer.task.hadoopWorkingPath	Temporary working directory for Hadoop tasks.	/tmp/druid-indexing
druid.indexer.task.restoreTasksOnRestart	If true, MiddleManagers will attempt to stop tasks gracefully on shutdown and restore them on restart.	false
druid.indexer.task.ignoreTimestampSpecForDruidInputSource	If true, tasks using the Druid input source will ignore the provided timestampSpec, and will use the __time column of the input datasource. This option is provided for compatibility with ingestion specs written before Druid 0.22.0.	false
druid.indexer.task.storeEmptyColumns	Boolean value for whether or not to store empty columns during ingestion. When set to true, Druid stores every column specified in the dimensionsSpec. If you use the string-based schemaless ingestion and don't specify any dimensions to ingest, you must also set includeAllDimensions for Druid to store empty columns. If you set storeEmptyColumns to false, Druid SQL queries referencing empty columns will fail. If you intend to leave storeEmptyColumns disabled, you should either ingest placeholder data for empty columns or else not query on empty columns. You can overwrite this configuration by setting storeEmptyColumns in the task context.	true
druid.indexer.task.tmpStorageBytesPerTask	Maximum number of bytes per task to be used to store temporary files on disk. This config is generally intended for internal usage. Attempts to set it are very likely to be overwritten by the TaskRunner that executes the task, so be sure of what you expect to happen before directly adjusting this configuration parameter. The config is documented here primarily to provide an understanding of what it means if/when someone sees that it has been set. A value of -1 disables this limit.	-1
druid.indexer.server.maxChatRequests	Maximum number of concurrent requests served by a task's chat handler. Set to 0 to disable limiting.	0

If the Peon is running in remote mode, there must be an Overlord up and running. Peons in remote mode can set the following configurations:

Property	Description	Default
druid.peon.taskActionClient.retry.minWait	The minimum retry time to communicate with Overlord.	PT5S
druid.peon.taskActionClient.retry.maxWait	The maximum retry time to communicate with Overlord.	PT1M
druid.peon.taskActionClient.retry.maxRetryCount	The maximum number of retries to communicate with Overlord.	60

SegmentWriteOutMediumFactory

When new segments are created, Druid temporarily stores some preprocessed data in some buffers. The following types of medium exist for the buffers:

• Temporary files (tmpFile) are stored under the task working directory (see druid.worker.baseTaskDirs configuration above) and thus share it's mounting properties. For example, they could be backed by HDD, SSD or memory (tmpfs). This type of medium may do unnecessary disk I/O and requires some disk space to be available.

• Off-heap memory (offHeapMemory) creates buffers in off-heap memory of a JVM process that is running a task. This type of medium is preferred, but it may require to allow the JVM to have more off-heap memory, by changing -XX:MaxDirectMemorySize configuration. It is not yet understood how does the required off-heap memory size relates to the size of the segments being created. But definitely it doesn't make sense to add more extra off-heap memory, than the configured maximum heap size (-Xmx) for the same JVM.

• On-heap memory (onHeapMemory) creates buffers using the allocated heap memory of the JVM process running a task. Using on-heap memory introduces garbage collection overhead and so is not recommended in most cases. This type of medium is most helpful for tasks run on external clusters where it may be difficult to allocate and work with direct memory effectively.

For most types of tasks, SegmentWriteOutMediumFactory can be configured per-task (see Tasks for more information), but if it's not specified for a task, or it's not supported for a particular task type, then Druid uses the value from the following configuration:

Property	Description	Default
druid.peon.defaultSegmentWriteOutMediumFactory.type	tmpFile, offHeapMemory, or onHeapMemory	tmpFile

Indexer

Indexer process configuration

Property	Description	Default
druid.host	The host for the current process. This is used to advertise the current processes location as reachable from another process and should generally be specified such that http://${druid.host}/ could actually talk to this process	InetAddress.getLocalHost().getCanonicalHostName()
druid.bindOnHost	Indicating whether the process's internal jetty server bind on druid.host. Default is false, which means binding to all interfaces.	false
druid.plaintextPort	This is the port to actually listen on; unless port mapping is used, this will be the same port as is on druid.host	8091
druid.tlsPort	TLS port for HTTPS connector, if druid.enableTlsPort is set then this config will be used. If druid.host contains port then that port will be ignored. This should be a non-negative Integer.	8283
druid.service	The name of the service. This is used as a dimension when emitting metrics and alerts to differentiate between the various services	druid/indexer

Indexer general configuration

Property	Description	Default
druid.worker.version	Version identifier for the Indexer.	0
druid.worker.capacity	Maximum number of tasks the Indexer can accept.	Number of available processors - 1
druid.worker.baseTaskDirs	List of base temporary working directories, one of which is assigned per task in a round-robin fashion. This property can be used to allow usage of multiple disks for indexing. This property is recommended in place of and takes precedence over ${druid.indexer.task.baseTaskDir}. If this configuration is not set, ${druid.indexer.task.baseTaskDir} is used. Example: druid.worker.baseTaskDirs=[\"PATH1\",\"PATH2\",...].	null
druid.worker.baseTaskDirSize	The total amount of bytes that can be used by tasks on any single task dir. This value is treated symmetrically across all directories, that is, if this is 500 GB and there are 3 baseTaskDirs, then each of those task directories is assumed to allow for 500 GB to be used and a total of 1.5 TB will potentially be available across all tasks. The actual amount of memory assigned to each task is discussed in Configuring task storage sizes	Long.MAX_VALUE
druid.worker.globalIngestionHeapLimitBytes	Total amount of heap available for ingestion processing. This is applied by automatically setting the maxBytesInMemory property on tasks.	Configured max JVM heap size / 6
druid.worker.numConcurrentMerges	Maximum number of segment persist or merge operations that can run concurrently across all tasks.	druid.worker.capacity / 2, rounded down
druid.indexer.task.baseDir	Base temporary working directory.	System.getProperty("java.io.tmpdir")
druid.indexer.task.baseTaskDir	Base temporary working directory for tasks.	${druid.indexer.task.baseDir}/persistent/tasks
druid.indexer.task.defaultHadoopCoordinates	Hadoop version to use with HadoopIndexTasks that do not request a particular version.	org.apache.hadoop:hadoop-client-api:3.3.6, org.apache.hadoop:hadoop-client-runtime:3.3.6
druid.indexer.task.gracefulShutdownTimeout	Wait this long on Indexer restart for restorable tasks to gracefully exit.	PT5M
druid.indexer.task.hadoopWorkingPath	Temporary working directory for Hadoop tasks.	/tmp/druid-indexing
druid.indexer.task.restoreTasksOnRestart	If true, the Indexer will attempt to stop tasks gracefully on shutdown and restore them on restart.	false
druid.indexer.task.ignoreTimestampSpecForDruidInputSource	If true, tasks using the Druid input source will ignore the provided timestampSpec, and will use the __time column of the input datasource. This option is provided for compatibility with ingestion specs written before Druid 0.22.0.	false
druid.indexer.task.storeEmptyColumns	Boolean value for whether or not to store empty columns during ingestion. When set to true, Druid stores every column specified in the dimensionsSpec. If you set storeEmptyColumns to false, Druid SQL queries referencing empty columns will fail. If you intend to leave storeEmptyColumns disabled, you should either ingest placeholder data for empty columns or else not query on empty columns. You can overwrite this configuration by setting storeEmptyColumns in the task context.	true
druid.peon.taskActionClient.retry.minWait	The minimum retry time to communicate with Overlord.	PT5S
druid.peon.taskActionClient.retry.maxWait	The maximum retry time to communicate with Overlord.	PT1M
druid.peon.taskActionClient.retry.maxRetryCount	The maximum number of retries to communicate with Overlord.	60

Indexer concurrent requests

Druid uses Jetty to serve HTTP requests.

Property	Description	Default
druid.server.http.numThreads	Number of threads for HTTP requests. Please see the Indexer Server HTTP threads documentation for more details on how the Indexer uses this configuration.	max(10, (Number of cores * 17) / 16 + 2) + 30
druid.server.http.queueSize	Size of the worker queue used by Jetty server to temporarily store incoming client connections. If this value is set and a request is rejected by jetty because queue is full then client would observe request failure with TCP connection being closed immediately with a completely empty response from server.	Unbounded
druid.server.http.maxIdleTime	The Jetty max idle time for a connection.	PT5M
druid.server.http.enableRequestLimit	If enabled, no requests would be queued in jetty queue and "HTTP 429 Too Many Requests" error response would be sent.	false
druid.server.http.defaultQueryTimeout	Query timeout in millis, beyond which unfinished queries will be cancelled	300000
druid.server.http.gracefulShutdownTimeout	The maximum amount of time Jetty waits after receiving shutdown signal. After this timeout the threads will be forcefully shutdown. This allows any queries that are executing to complete(Only values greater than zero are valid).	PT30S
druid.server.http.unannouncePropagationDelay	How long to wait for ZooKeeper unannouncements to propagate before shutting down Jetty. This is a minimum and druid.server.http.gracefulShutdownTimeout does not start counting down until after this period elapses.	PT0S (do not wait)
druid.server.http.maxQueryTimeout	Maximum allowed value (in milliseconds) for timeout parameter. See query-context to know more about timeout. Query is rejected if the query context timeout is greater than this value.	Long.MAX_VALUE
druid.server.http.maxRequestHeaderSize	Maximum size of a request header in bytes. Larger headers consume more memory and can make a server more vulnerable to denial of service attacks.	8 * 1024
druid.server.http.enableForwardedRequestCustomizer	If enabled, adds Jetty ForwardedRequestCustomizer which reads X-Forwarded-* request headers to manipulate servlet request object when Druid is used behind a proxy.	false
druid.server.http.allowedHttpMethods	List of HTTP methods that should be allowed in addition to the ones required by Druid APIs. Druid APIs require GET, PUT, POST, and DELETE, which are always allowed. This option is not useful unless you have installed an extension that needs these additional HTTP methods or that adds functionality related to CORS. None of Druid's bundled extensions require these methods.	[]
druid.server.http.contentSecurityPolicy	Content-Security-Policy header value to set on each non-POST response. Setting this property to an empty string, or omitting it, both result in the default frame-ancestors: none being set.	frame-ancestors 'none'

Indexer processing resources

Property	Description	Default
druid.processing.buffer.sizeBytes	This specifies a buffer size (less than 2GiB) for the storage of intermediate results. The computation engine in the Indexer processes will use a scratch buffer of this size to do all of their intermediate computations off-heap. Larger values allow for more aggregations in a single pass over the data while smaller values can require more passes depending on the query that is being executed. Human-readable format is supported.	auto (max 1GiB)
druid.processing.buffer.poolCacheMaxCount	processing buffer pool caches the buffers for later use, this is the maximum count cache will grow to. note that pool can create more buffers than it can cache if necessary.	Integer.MAX_VALUE
druid.processing.formatString	Indexer processes use this format string to name their processing threads.	processing-%s
druid.processing.numMergeBuffers	The number of direct memory buffers available for merging query results. The buffers are sized by druid.processing.buffer.sizeBytes. This property is effectively a concurrency limit for queries that require merging buffers. If you are using any queries that require merge buffers (currently, just groupBy) then you should have at least two of these.	max(2, druid.processing.numThreads / 4)
druid.processing.numThreads	The number of processing threads to have available for parallel processing of segments. Our rule of thumb is num_cores - 1, which means that even under heavy load there will still be one core available to do background tasks like talking with ZooKeeper and pulling down segments. If only one core is available, this property defaults to the value 1.	Number of cores - 1 (or 1)
druid.processing.fifo	If the processing queue should treat tasks of equal priority in a FIFO manner	true
druid.processing.tmpDir	Path where temporary files created while processing a query should be stored. If specified, this configuration takes priority over the default java.io.tmpdir path.	path represented by java.io.tmpdir

The amount of direct memory needed by Druid is at least druid.processing.buffer.sizeBytes * (druid.processing.numMergeBuffers + druid.processing.numThreads + 1). You can ensure at least this amount of direct memory is available by providing -XX:MaxDirectMemorySize=<VALUE> at the command line.

Query configurations

See general query configuration.

Indexer caching

You can optionally configure caching to be enabled on the Indexer by setting caching configs here.

Property	Possible Values	Description	Default
druid.realtime.cache.useCache	true, false	Enable the cache on the realtime.	false
druid.realtime.cache.populateCache	true, false	Populate the cache on the realtime.	false
druid.realtime.cache.unCacheable	All druid query types	All query types to not cache.	[]
druid.realtime.cache.maxEntrySize	positive integer	Maximum cache entry size in bytes.	1_000_000

See cache configuration for how to configure cache settings.

Note that only local caches such as the local-type cache and caffeine cache are supported. If a remote cache such as memcached is used, it will be ignored.

Historical

For general Historical service information, see Historical.

These Historical configurations can be defined in the historical/runtime.properties file.

Historical service configuration

Property	Description	Default
druid.host	The host for the current service. This is used to advertise the current service location as reachable from another service and should generally be specified such that http://${druid.host}/ could actually talk to this service	InetAddress.getLocalHost().getCanonicalHostName()
druid.bindOnHost	Indicating whether the service's internal jetty server bind on druid.host. Default is false, which means binding to all interfaces.	false
druid.plaintextPort	This is the port to actually listen on; unless port mapping is used, this will be the same port as is on druid.host	8083
druid.tlsPort	TLS port for HTTPS connector, if druid.enableTlsPort is set then this config will be used. If druid.host contains port then that port will be ignored. This should be a non-negative Integer.	8283
druid.service	The name of the service. This is used as a dimension when emitting metrics and alerts to differentiate between the various services	druid/historical

Historical general configuration

Property	Description	Default
druid.server.maxSize	The maximum number of bytes-worth of segments that the service wants assigned to it. The Coordinator service will attempt to assign segments to a Historical service only if this property is greater than the total size of segments served by it. Since this property defines the upper limit on the total segment size that can be assigned to a Historical, it is defaulted to the sum of all maxSize values specified within druid.segmentCache.locations property. Human-readable format is supported, see here.	Sum of maxSize values defined within druid.segmentCache.locations
druid.server.tier	A string to name the distribution tier that the storage service belongs to. Many of the rules Coordinator services use to manage segments can be keyed on tiers.	_default_tier
druid.server.priority	In a tiered architecture, the priority of the tier, thus allowing control over which services are queried. Higher numbers mean higher priority. The default (no priority) works for architecture with no cross replication (tiers that have no data-storage overlap). Data centers typically have equal priority.	0

Storing segments

Property	Description	Default
druid.segmentCache.locations	Segments assigned to a Historical services are first stored on the local file system (in a disk cache) and then served by the Historical services. These locations define where that local cache resides. This value cannot be NULL or EMPTY. Here is an example druid.segmentCache.locations=[{"path": "/mnt/druidSegments", "maxSize": "10k", "freeSpacePercent": 1.0}]. "freeSpacePercent" is optional, if provided then enforces that much of free disk partition space while storing segments. But, it depends on File.getTotalSpace() and File.getFreeSpace() methods, so enable if only if they work for your File System.	none
druid.segmentCache.locationSelector.strategy	The strategy used to select a location from the configured druid.segmentCache.locations for segment distribution. Possible values are leastBytesUsed, roundRobin, random, or mostAvailableSize.	leastBytesUsed
druid.segmentCache.deleteOnRemove	Delete segment files from cache once a service is no longer serving a segment.	true
druid.segmentCache.dropSegmentDelayMillis	How long a service delays before completely dropping segment.	30000 (30 seconds)
druid.segmentCache.infoDir	Historical services keep track of the segments they are serving so that when the service is restarted they can reload the same segments without waiting for the Coordinator to reassign. This path defines where this metadata is kept. Directory will be created if needed.	${first_location}/info_dir
druid.segmentCache.announceIntervalMillis	How frequently to announce segments while segments are loading from cache. Set this value to zero to wait for all segments to be loaded before announcing.	5000 (5 seconds)
druid.segmentCache.numLoadingThreads	How many segments to drop or load concurrently from deep storage. Note that the work of loading segments involves downloading segments from deep storage, decompressing them and loading them to a memory mapped location. So the work is not all I/O Bound. Depending on CPU and network load, one could possibly increase this config to a higher value.	max(1,Number of cores / 6)
druid.segmentCache.numBootstrapThreads	How many segments to load concurrently during historical startup.	druid.segmentCache.numLoadingThreads
druid.segmentCache.lazyLoadOnStart	Whether or not to load segment columns metadata lazily during historical startup. When set to true, Historical startup time will be dramatically improved by deferring segment loading until the first time that segment takes part in a query, which will incur this cost instead.	false
druid.segmentCache.numThreadsToLoadSegmentsIntoPageCacheOnDownload	Number of threads to asynchronously read segment index files into null output stream on each new segment download after the Historical service finishes bootstrapping. Recommended to set to 1 or 2 or leave unspecified to disable. See also druid.segmentCache.numThreadsToLoadSegmentsIntoPageCacheOnBootstrap	0
druid.segmentCache.numThreadsToLoadSegmentsIntoPageCacheOnBootstrap	Number of threads to asynchronously read segment index files into null output stream during Historical service bootstrap. This thread pool is terminated after Historical service finishes bootstrapping. Recommended to set to half of available cores. If left unspecified, druid.segmentCache.numThreadsToLoadSegmentsIntoPageCacheOnDownload will be used. If both configs are unspecified, this feature is disabled. Preemptively loading segments into page cache helps in the sense that later when a segment is queried, it's already in page cache and only a minor page fault needs to be triggered instead of a more costly major page fault to make the query latency more consistent. Note that loading segment into page cache just does a blind loading of segment index files and will evict any existing segments from page cache at the discretion of operating system when the total segment size on local disk is larger than the page cache usable in the RAM, which roughly equals to total available RAM in the host - druid process memory including both heap and direct memory allocated - memory used by other non druid processes on the host, so it is the user's responsibility to ensure the host has enough RAM to host all the segments to avoid random evictions to fully leverage this feature.	druid.segmentCache.numThreadsToLoadSegmentsIntoPageCacheOnDownload

In druid.segmentCache.locations, freeSpacePercent was added because the maxSize setting is only a theoretical limit and assumes that much space will always be available for storing segments. In case of any druid bug leading to unaccounted segment files left alone on disk or some other service writing stuff to disk, This check can start failing segment loading early before filling up the disk completely and leaving the host usable otherwise.

In druid.segmentCache.locationSelector.strategy, one of leastBytesUsed, roundRobin, random, or mostAvailableSize could be specified to represent the strategy to distribute segments across multiple segment cache locations.

Strategy	Description
leastBytesUsed	Selects a location which has least bytes used in absolute terms.
roundRobin	Selects a location in a round robin fashion oblivious to the bytes used or the capacity.
random	Selects a segment cache location randomly each time among the available storage locations.
mostAvailableSize	Selects a segment cache location that has most free space among the available storage locations.

Note that if druid.segmentCache.numLoadingThreads > 1, multiple threads can download different segments at the same time. In this case, with the leastBytesUsed strategy or mostAvailableSize strategy, Historicals may select a sub-optimal storage location because each decision is based on a snapshot of the storage location status of when a segment is requested to download.

Historical query configs

Concurrent requests

Druid uses Jetty to serve HTTP requests.

Property	Description	Default
druid.server.http.numThreads	Number of threads for HTTP requests.	max(10, (Number of cores * 17) / 16 + 2) + 30
druid.server.http.queueSize	Size of the worker queue used by Jetty server to temporarily store incoming client connections. If this value is set and a request is rejected by jetty because queue is full then client would observe request failure with TCP connection being closed immediately with a completely empty response from server.	Unbounded
druid.server.http.maxIdleTime	The Jetty max idle time for a connection.	PT5M
druid.server.http.enableRequestLimit	If enabled, no requests would be queued in jetty queue and "HTTP 429 Too Many Requests" error response would be sent.	false
druid.server.http.defaultQueryTimeout	Query timeout in millis, beyond which unfinished queries will be cancelled	300000
druid.server.http.gracefulShutdownTimeout	The maximum amount of time Jetty waits after receiving shutdown signal. After this timeout the threads will be forcefully shutdown. This allows any queries that are executing to complete(Only values greater than zero are valid).	PT30S
druid.server.http.unannouncePropagationDelay	How long to wait for ZooKeeper unannouncements to propagate before shutting down Jetty. This is a minimum and druid.server.http.gracefulShutdownTimeout does not start counting down until after this period elapses.	PT0S (do not wait)
druid.server.http.maxQueryTimeout	Maximum allowed value (in milliseconds) for timeout parameter. See query-context to know more about timeout. Query is rejected if the query context timeout is greater than this value.	Long.MAX_VALUE
druid.server.http.maxRequestHeaderSize	Maximum size of a request header in bytes. Larger headers consume more memory and can make a server more vulnerable to denial of service attacks.	8 * 1024
druid.server.http.contentSecurityPolicy	Content-Security-Policy header value to set on each non-POST response. Setting this property to an empty string, or omitting it, both result in the default frame-ancestors: none being set.	frame-ancestors 'none'

Processing

Property	Description	Default
druid.processing.buffer.sizeBytes	This specifies a buffer size (less than 2GiB), for the storage of intermediate results. The computation engine in both the Historical and Realtime processes will use a scratch buffer of this size to do all of their intermediate computations off-heap. Larger values allow for more aggregations in a single pass over the data while smaller values can require more passes depending on the query that is being executed. Human-readable format is supported.	auto (max 1GiB)
druid.processing.buffer.poolCacheMaxCount	processing buffer pool caches the buffers for later use, this is the maximum count cache will grow to. note that pool can create more buffers than it can cache if necessary.	Integer.MAX_VALUE
druid.processing.formatString	Realtime and Historical processes use this format string to name their processing threads.	processing-%s
druid.processing.numMergeBuffers	The number of direct memory buffers available for merging query results. The buffers are sized by druid.processing.buffer.sizeBytes. This property is effectively a concurrency limit for queries that require merging buffers. If you are using any queries that require merge buffers (currently, just groupBy) then you should have at least two of these.	max(2, druid.processing.numThreads / 4)
druid.processing.numThreads	The number of processing threads to have available for parallel processing of segments. Our rule of thumb is num_cores - 1, which means that even under heavy load there will still be one core available to do background tasks like talking with ZooKeeper and pulling down segments. If only one core is available, this property defaults to the value 1.	Number of cores - 1 (or 1)
druid.processing.fifo	If the processing queue should treat tasks of equal priority in a FIFO manner	true
druid.processing.tmpDir	Path where temporary files created while processing a query should be stored. If specified, this configuration takes priority over the default java.io.tmpdir path.	path represented by java.io.tmpdir

The amount of direct memory needed by Druid is at least druid.processing.buffer.sizeBytes * (druid.processing.numMergeBuffers + druid.processing.numThreads + 1). You can ensure at least this amount of direct memory is available by providing -XX:MaxDirectMemorySize=<VALUE> at the command line.

Historical query configuration

See general query configuration.

Historical caching

You can optionally only configure caching to be enabled on the Historical by setting caching configs here.

Property	Possible Values	Description	Default
druid.historical.cache.useCache	true, false	Enable the cache on the Historical.	false
druid.historical.cache.populateCache	true, false	Populate the cache on the Historical.	false
druid.historical.cache.unCacheable	All druid query types	All query types to not cache.	[]
druid.historical.cache.maxEntrySize	positive integer	Maximum cache entry size in bytes.	1_000_000

See cache configuration for how to configure cache settings.

Query server

This section contains the configuration options for the services that reside on Query servers (Brokers) in the suggested three-server configuration.

Configuration options for the experimental Router process are also provided here.

Broker

For general Broker process information, see here.

These Broker configurations can be defined in the broker/runtime.properties file.

Broker process configs

Property	Description	Default
druid.host	The host for the current process. This is used to advertise the current processes location as reachable from another process and should generally be specified such that http://${druid.host}/ could actually talk to this process	InetAddress.getLocalHost().getCanonicalHostName()
druid.bindOnHost	Indicating whether the process's internal jetty server bind on druid.host. Default is false, which means binding to all interfaces.	false
druid.plaintextPort	This is the port to actually listen on; unless port mapping is used, this will be the same port as is on druid.host	8082
druid.tlsPort	TLS port for HTTPS connector, if druid.enableTlsPort is set then this config will be used. If druid.host contains port then that port will be ignored. This should be a non-negative Integer.	8282
druid.service	The name of the service. This is used as a dimension when emitting metrics and alerts to differentiate between the various services	druid/broker

Query configuration

Query routing

Property	Possible Values	Description	Default
druid.broker.balancer.type	random, connectionCount	Determines how the broker balances connections to Historical processes. random choose randomly, connectionCount picks the process with the fewest number of active connections to	random
druid.broker.select.tier	highestPriority, lowestPriority, custom	If segments are cross-replicated across tiers in a cluster, you can tell the broker to prefer to select segments in a tier with a certain priority.	highestPriority
druid.broker.select.tier.custom.priorities	An array of integer priorities, such as [-1, 0, 1, 2]	Select servers in tiers with a custom priority list.	The config only has effect if druid.broker.select.tier is set to custom. If druid.broker.select.tier is set to custom but this config is not specified, the effect is the same as druid.broker.select.tier set to highestPriority. Any of the integers in this config can be ignored if there's no corresponding tiers with such priorities. Tiers with priorities explicitly specified in this config always have higher priority than those not and those not specified fall back to use highestPriority strategy among themselves.

Query prioritization and laning

Laning strategies allow you to control capacity utilization for heterogeneous query workloads. With laning, the broker examines and classifies a query for the purpose of assigning it to a lane. Lanes have capacity limits, enforced by the broker, that can be used to ensure sufficient resources are available for other lanes or for interactive queries (with no lane), or to limit overall throughput for queries within the lane. Requests in excess of the capacity are discarded with an HTTP 429 status code.

Property	Description	Default
druid.query.scheduler.numThreads	Maximum number of concurrently-running queries. When this parameter is set lower than druid.server.http.numThreads, query requests beyond the limit are put into the Jetty request queue. This has the effect of reserving the leftover Jetty threads for non-query requests. When this parameter is set equal to or higher than druid.server.http.numThreads, it has no effect.	Unbounded
druid.query.scheduler.laning.strategy	Query laning strategy to use to assign queries to a lane in order to control capacities for certain classes of queries.	none
druid.query.scheduler.prioritization.strategy	Query prioritization strategy to automatically assign priorities.	manual

Prioritization strategies

Manual prioritization strategy

With this configuration, queries are never assigned a priority automatically, but will preserve a priority manually set on the query context with the priority key. This mode can be explicitly set by setting druid.query.scheduler.prioritization.strategy to manual.

Threshold prioritization strategy

This prioritization strategy lowers the priority of queries that cross any of a configurable set of thresholds, such as how far in the past the data is, how large of an interval a query covers, or the number of segments taking part in a query.

This strategy can be enabled by setting druid.query.scheduler.prioritization.strategy to threshold.

Property	Description	Default
druid.query.scheduler.prioritization.periodThreshold	ISO duration threshold for how old data can be queried before automatically adjusting query priority.	none
druid.query.scheduler.prioritization.durationThreshold	ISO duration threshold for maximum duration a queries interval can span before the priority is automatically adjusted.	none
druid.query.scheduler.prioritization.segmentCountThreshold	Number threshold for maximum number of segments that can take part in a query before its priority is automatically adjusted.	none
druid.query.scheduler.prioritization.adjustment	Amount to reduce the priority of queries which cross any threshold.	none

Laning strategies

No laning strategy

In this mode, queries are never assigned a lane, and the concurrent query count will only be limited by druid.server.http.numThreads or druid.query.scheduler.numThreads, if set. This is the default Druid query scheduler operating mode. Enable this strategy explicitly by setting druid.query.scheduler.laning.strategy to none.

'High/Low' laning strategy

This laning strategy splits queries with a priority below zero into a low query lane, automatically. Queries with priority of zero (the default) or above are considered 'interactive'. The limit on low queries can be set to some desired percentage of the total capacity (or HTTP thread pool size), reserving capacity for interactive queries. Queries in the low lane are not guaranteed their capacity, which may be consumed by interactive queries, but may use up to this limit if total capacity is available.

If the low lane is specified in the query context lane parameter, this will override the computed lane.

This strategy can be enabled by setting druid.query.scheduler.laning.strategy=hilo.

Property	Description	Default
druid.query.scheduler.laning.maxLowPercent	Maximum percent of the smaller number of druid.server.http.numThreads or druid.query.scheduler.numThreads, defining the number of HTTP threads that can be used by queries with a priority lower than 0. Value must be an integer in the range 1 to 100, and will be rounded up	No default, must be set if using this mode

Guardrails for materialization of subqueries

Druid stores the subquery rows in temporary tables that live in the Java heap. It is a good practice to avoid large subqueries in Druid. Therefore, there are guardrails that are built in Druid to prevent the queries from generating subquery results which can exhaust the heap space. They can be set on a cluster level or modified per query level as desired. Note the following guardrails that can be set by the cluster admin to limit the subquery results:

1. druid.server.http.maxSubqueryRows in broker's config to set a default for the entire cluster or maxSubqueryRows in the query context to set an upper limit on the number of rows a subquery can generate
2. druid.server.http.maxSubqueryBytes in broker's config to set a default for the entire cluster or maxSubqueryBytes in the query context to set an upper limit on the number of bytes a subquery can generate

Limiting the subquery by bytes is an experimental feature as it materializes the results differently.

You can configure maxSubqueryBytes to the following values:

• disabled: It is the default setting out of the box. It disables the subquery's from the byte based limit, and effectively disables this feature.
• auto: Druid automatically decides the optimal byte based limit based upon the heap space available and the max number of concurrent queries.
• A positive long value: User can manually specify the number of bytes that the results of the subqueries of a single query can occupy on the heap.

Due to the conversion between the Java objects and the Frame's format, setting maxSubqueryBytes can become slow if the subquery starts generating rows in the order of magnitude of around 10 million and above. In those scenarios, disable the maxSubqueryBytes settings for such queries, assess the number of rows that the subqueries generate and override the maxSubqueryRows to appropriate value.

If you choose to modify or set any of the above limits, you must also think about the heap size of all Brokers, Historicals, and task Peons that process data for the subqueries to accommodate the subquery results. There is no formula to calculate the correct value. Trial and error is the best approach.

Manual laning strategy

This laning strategy is best suited for cases where one or more external applications which query Druid are capable of manually deciding what lane a given query should belong to. Configured with a map of lane names to percent or exact max capacities, queries with a matching lane parameter in the query context will be subjected to those limits.

Property	Description	Default
druid.query.scheduler.laning.lanes.{name}	Maximum percent or exact limit of queries that can concurrently run in the defined lanes. Any number of lanes may be defined like this. The lane names 'total' and 'default' are reserved for internal use.	No default, must define at least one lane with a limit above 0. If druid.query.scheduler.laning.isLimitPercent is set to true, values must be integers in the range of 1 to 100.
druid.query.scheduler.laning.isLimitPercent	If set to true, the values set for druid.query.scheduler.laning.lanes will be treated as a percent of the smaller number of druid.server.http.numThreads or druid.query.scheduler.numThreads. Note that in this mode, these lane values across lanes are not required to add up to, and can exceed, 100%.	false

Server configuration

Druid uses Jetty to serve HTTP requests. Each query being processed consumes a single thread from druid.server.http.numThreads, so consider defining druid.query.scheduler.numThreads to a lower value in order to reserve HTTP threads for responding to health checks, lookup loading, and other non-query, (in most cases) comparatively very short-lived, HTTP requests.

Property	Description	Default
druid.server.http.numThreads	Number of threads for HTTP requests.	max(10, (Number of cores * 17) / 16 + 2) + 30
druid.server.http.queueSize	Size of the worker queue used by Jetty server to temporarily store incoming client connections. If this value is set and a request is rejected by jetty because queue is full then client would observe request failure with TCP connection being closed immediately with a completely empty response from server.	Unbounded
druid.server.http.maxIdleTime	The Jetty max idle time for a connection.	PT5M
druid.server.http.enableRequestLimit	If enabled, no requests would be queued in jetty queue and "HTTP 429 Too Many Requests" error response would be sent.	false
druid.server.http.defaultQueryTimeout	Query timeout in millis, beyond which unfinished queries will be cancelled	300000
druid.server.http.maxScatterGatherBytes	Maximum number of bytes gathered from data processes such as Historicals and realtime processes to execute a query. Queries that exceed this limit will fail. This is an advance configuration that allows to protect in case Broker is under heavy load and not utilizing the data gathered in memory fast enough and leading to OOMs. This limit can be further reduced at query time using maxScatterGatherBytes in the context. Note that having large limit is not necessarily bad if broker is never under heavy concurrent load in which case data gathered is processed quickly and freeing up the memory used. Human-readable format is supported, see here.	Long.MAX_VALUE
druid.server.http.maxSubqueryRows	Maximum number of rows from all subqueries per query. Druid stores the subquery rows in temporary tables that live in the Java heap. druid.server.http.maxSubqueryRows is a guardrail to prevent the system from exhausting available heap. When a subquery exceeds the row limit, Druid throws a resource limit exceeded exception: "Subquery generated results beyond maximum." It is a good practice to avoid large subqueries in Druid. However, if you choose to raise the subquery row limit, you must also increase the heap size of all Brokers, Historicals, and task Peons that process data for the subqueries to accommodate the subquery results. There is no formula to calculate the correct value. Trial and error is the best approach.	100000
druid.server.http.maxSubqueryBytes	Maximum number of bytes from all subqueries per query. Since the results are stored on the Java heap, druid.server.http.maxSubqueryBytes is a guardrail like druid.server.http.maxSubqueryRows to prevent the heap space from exhausting. When a subquery exceeds the byte limit, Druid throws a resource limit exceeded exception. A negative value for the guardrail indicates that Druid won't guardrail by memory. This can be set to 'disabled' which disables the results from being limited via the byte limit, 'auto' which sets this value automatically taking free heap space into account, or a positive long value depicting the number of bytes per query's subqueries' results can occupy. This is an experimental feature for now as this materializes the results in a different format.	'disabled'
druid.server.http.gracefulShutdownTimeout	The maximum amount of time Jetty waits after receiving shutdown signal. After this timeout the threads will be forcefully shutdown. This allows any queries that are executing to complete(Only values greater than zero are valid).	PT30S
druid.server.http.unannouncePropagationDelay	How long to wait for ZooKeeper unannouncements to propagate before shutting down Jetty. This is a minimum and druid.server.http.gracefulShutdownTimeout does not start counting down until after this period elapses.	PT0S (do not wait)
druid.server.http.maxQueryTimeout	Maximum allowed value (in milliseconds) for timeout parameter. See query-context to know more about timeout. Query is rejected if the query context timeout is greater than this value.	Long.MAX_VALUE
druid.server.http.maxRequestHeaderSize	Maximum size of a request header in bytes. Larger headers consume more memory and can make a server more vulnerable to denial of service attacks.	8 * 1024
druid.server.http.contentSecurityPolicy	Content-Security-Policy header value to set on each non-POST response. Setting this property to an empty string, or omitting it, both result in the default frame-ancestors: none being set.	frame-ancestors 'none'
druid.server.http.enableHSTS	If set to true, druid services will add strict transport security header Strict-Transport-Security: max-age=63072000; includeSubDomains to all HTTP responses	false

Client configuration

Druid Brokers use an HTTP client to communicate with data servers (Historical servers and real-time tasks). This client has the following configuration options.

Property	Description	Default
druid.broker.http.numConnections	Size of connection pool for the Broker to connect to Historical and real-time processes. If there are more queries than this number that all need to speak to the same process, then they will queue up.	20
druid.broker.http.eagerInitialization	Indicates that http connections from Broker to Historical and Real-time processes should be eagerly initialized. If set to true, numConnections connections are created upon initialization	true
druid.broker.http.compressionCodec	Compression codec the Broker uses to communicate with Historical and real-time processes. May be "gzip" or "identity".	gzip
druid.broker.http.readTimeout	The timeout for data reads from Historical servers and real-time tasks.	PT15M
druid.broker.http.unusedConnectionTimeout	The timeout for idle connections in connection pool. The connection in the pool will be closed after this timeout and a new one will be established. This timeout should be less than druid.broker.http.readTimeout. Set this timeout = ~90% of druid.broker.http.readTimeout	PT4M
druid.broker.http.maxQueuedBytes	Maximum number of bytes queued per query before exerting backpressure on channels to the data servers. Similar to druid.server.http.maxScatterGatherBytes, except that maxQueuedBytes triggers backpressure instead of query failure. Set to zero to disable. You can override this setting by using the maxQueuedBytes query context parameter. Druid supports human-readable format.	25 MB or 2% of maximum Broker heap size, whichever is greater.
druid.broker.http.numMaxThreads	`Maximum number of I/O worker threads	max(10, ((number of cores * 17) / 16 + 2) + 30)`

Retry policy

Druid broker can optionally retry queries internally for transient errors.

Property	Description	Default
druid.broker.retryPolicy.numTries	Number of tries.	1

Processing

The broker uses processing configs for nested groupBy queries.

Property	Description	Default
druid.processing.buffer.sizeBytes	This specifies a buffer size (less than 2GiB) for the storage of intermediate results. The computation engine in both the Historical and Realtime processes will use a scratch buffer of this size to do all of their intermediate computations off-heap. Larger values allow for more aggregations in a single pass over the data while smaller values can require more passes depending on the query that is being executed. Human-readable format is supported.	auto (max 1GiB)
druid.processing.buffer.poolCacheInitialCount	initializes the number of buffers allocated on the intermediate results pool. Note that pool can create more buffers if necessary.	0
druid.processing.buffer.poolCacheMaxCount	processing buffer pool caches the buffers for later use, this is the maximum count cache will grow to. note that pool can create more buffers than it can cache if necessary.	Integer.MAX_VALUE
druid.processing.numMergeBuffers	The number of direct memory buffers available for merging query results. The buffers are sized by druid.processing.buffer.sizeBytes. This property is effectively a concurrency limit for queries that require merging buffers. If you are using any queries that require merge buffers (currently, just groupBy) then you should have at least two of these.	max(2, druid.processing.numThreads / 4)
druid.processing.fifo	If the processing queue should treat tasks of equal priority in a FIFO manner	true
druid.processing.tmpDir	Path where temporary files created while processing a query should be stored. If specified, this configuration takes priority over the default java.io.tmpdir path.	path represented by java.io.tmpdir
druid.processing.merge.useParallelMergePool	Enable automatic parallel merging for Brokers on a dedicated async ForkJoinPool. If false, instead merges will be done serially on the HTTP thread pool.	true
druid.processing.merge.pool.parallelism	Size of ForkJoinPool. Note that the default configuration assumes that the value returned by Runtime.getRuntime().availableProcessors() represents 2 hyper-threads per physical core, and multiplies this value by 0.75 in attempt to size 1.5 times the number of physical cores.	Runtime.getRuntime().availableProcessors() * 0.75 (rounded up)
druid.processing.merge.pool.defaultMaxQueryParallelism	Default maximum number of parallel merge tasks per query. Note that the default configuration assumes that the value returned by Runtime.getRuntime().availableProcessors() represents 2 hyper-threads per physical core, and multiplies this value by 0.5 in attempt to size to the number of physical cores.	Runtime.getRuntime().availableProcessors() * 0.5 (rounded up)
druid.processing.merge.pool.awaitShutdownMillis	Time to wait for merge ForkJoinPool tasks to complete before ungracefully stopping on process shutdown in milliseconds.	60_000
druid.processing.merge.task.targetRunTimeMillis	Ideal run-time of each ForkJoinPool merge task, before forking off a new task to continue merging sequences.	100
druid.processing.merge.task.initialYieldNumRows	Number of rows to yield per ForkJoinPool merge task, before forking off a new task to continue merging sequences.	16384
druid.processing.merge.task.smallBatchNumRows	Size of result batches to operate on in ForkJoinPool merge tasks.	4096

The amount of direct memory needed by Druid is at least druid.processing.buffer.sizeBytes * (druid.processing.numMergeBuffers + 1). You can ensure at least this amount of direct memory is available by providing -XX:MaxDirectMemorySize=<VALUE> at the command line.

Broker query configuration

See general query configuration.

Broker generated query configuration supplementation

The Broker generates queries internally. This configuration section describes how an operator can augment the configuration of these queries.

As of now the only supported augmentation is overriding the default query context. This allows an operator the flexibility to adjust it as they see fit. A common use of this configuration is to override the query priority of the cluster generated queries in order to avoid running as a default priority of 0.

Property	Description	Default
druid.broker.internal.query.config.context	A string formatted key:value map of a query context to add to internally generated broker queries.	null

SQL

The Druid SQL server is configured through the following properties on the Broker.

Property	Description	Default
druid.sql.enable	Whether to enable SQL at all, including background metadata fetching. If false, this overrides all other SQL-related properties and disables SQL metadata, serving, and planning completely.	true
druid.sql.avatica.enable	Whether to enable JDBC querying at /druid/v2/sql/avatica/.	true
druid.sql.avatica.maxConnections	Maximum number of open connections for the Avatica server. These are not HTTP connections, but are logical client connections that may span multiple HTTP connections.	25
druid.sql.avatica.maxRowsPerFrame	Maximum acceptable value for the JDBC client Statement.setFetchSize method. This setting determines the maximum number of rows that Druid will populate in a single 'fetch' for a JDBC ResultSet. Set this property to -1 to enforce no row limit on the server-side and potentially return the entire set of rows on the initial statement execution. If the JDBC client calls Statement.setFetchSize with a value other than -1, Druid uses the lesser value of the client-provided limit and maxRowsPerFrame. If maxRowsPerFrame is smaller than minRowsPerFrame, then the ResultSet size will be fixed. To handle queries that produce results with a large number of rows, you can increase value of druid.sql.avatica.maxRowsPerFrame to reduce the number of fetches required to completely transfer the result set.	5,000
druid.sql.avatica.minRowsPerFrame	Minimum acceptable value for the JDBC client Statement.setFetchSize method. The value for this property must greater than 0. If the JDBC client calls Statement.setFetchSize with a lesser value, Druid uses minRowsPerFrame instead. If maxRowsPerFrame is less than minRowsPerFrame, Druid uses the minimum value of the two. For handling queries which produce results with a large number of rows, you can increase this value to reduce the number of fetches required to completely transfer the result set.	100
druid.sql.avatica.maxStatementsPerConnection	Maximum number of simultaneous open statements per Avatica client connection.	4
druid.sql.avatica.connectionIdleTimeout	Avatica client connection idle timeout.	PT5M
druid.sql.avatica.fetchTimeoutMs	Avatica fetch timeout, in milliseconds. When a request for the next batch of data takes longer than this time, Druid returns an empty result set, causing the client to poll again. This avoids HTTP timeouts for long-running queries. The default of 5 sec. is good for most cases.	5000
druid.sql.http.enable	Whether to enable JSON over HTTP querying at /druid/v2/sql/.	true
druid.sql.planner.maxTopNLimit	Maximum threshold for a TopN query. Higher limits will be planned as GroupBy queries instead.	100000
druid.sql.planner.metadataRefreshPeriod	Throttle for metadata refreshes.	PT1M
druid.sql.planner.metadataColumnTypeMergePolicy	Defines how column types will be chosen when faced with differences between segments when computing the SQL schema. Options are specified as a JSON object, with valid choices of leastRestrictive or latestInterval. For leastRestrictive, Druid will automatically widen the type computed for the schema to a type which data across all segments can be converted into, however planned schema migrations can only take effect once all segments have been re-ingested to the new schema. With latestInterval, the column type in most recent time chunks defines the type for the schema.	leastRestrictive
druid.sql.planner.useApproximateCountDistinct	Whether to use an approximate cardinality algorithm for COUNT(DISTINCT foo).	true
druid.sql.planner.useGroupingSetForExactDistinct	Only relevant when useApproximateCountDistinct is disabled. If set to true, exact distinct queries are re-written using grouping sets. Otherwise, exact distinct queries are re-written using joins. This should be set to true for group by query with multiple exact distinct aggregations. This flag can be overridden per query.	false
druid.sql.planner.useApproximateTopN	Whether to use approximate TopN queries when a SQL query could be expressed as such. If false, exact GroupBy queries will be used instead.	true
druid.sql.planner.requireTimeCondition	Whether to require SQL to have filter conditions on __time column so that all generated native queries will have user specified intervals. If true, all queries without filter condition on __time column will fail	false
druid.sql.planner.sqlTimeZone	Sets the default time zone for the server, which will affect how time functions and timestamp literals behave. Should be a time zone name like "America/Los_Angeles" or offset like "-08:00".	UTC
druid.sql.planner.metadataSegmentCacheEnable	Whether to keep a cache of published segments in broker. If true, broker polls coordinator in background to get segments from metadata store and maintains a local cache. If false, coordinator's REST API will be invoked when broker needs published segments info.	false
druid.sql.planner.metadataSegmentPollPeriod	How often to poll coordinator for published segments list if druid.sql.planner.metadataSegmentCacheEnable is set to true. Poll period is in milliseconds.	60000
druid.sql.planner.authorizeSystemTablesDirectly	If true, Druid authorizes queries against any of the system schema tables (sys in SQL) as SYSTEM_TABLE resources which require READ access, in addition to permissions based content filtering.	false
druid.sql.planner.useNativeQueryExplain	If true, EXPLAIN PLAN FOR will return the explain plan as a JSON representation of equivalent native query(s), else it will return the original version of explain plan generated by Calcite. It can be overridden per query with useNativeQueryExplain context key.	true
druid.sql.planner.maxNumericInFilters	Max limit for the amount of numeric values that can be compared for a string type dimension when the entire SQL WHERE clause of a query translates to an OR of Bound filter. By default, Druid does not restrict the amount of numeric Bound Filters on String columns, although this situation may block other queries from running. Set this property to a smaller value to prevent Druid from running queries that have prohibitively long segment processing times. The optimal limit requires some trial and error; we recommend starting with 100. Users who submit a query that exceeds the limit of maxNumericInFilters should instead rewrite their queries to use strings in the WHERE clause instead of numbers. For example, WHERE someString IN (‘123’, ‘456’). If this value is disabled, maxNumericInFilters set through query context is ignored.	-1 (disabled)
druid.sql.approxCountDistinct.function	Implementation to use for the APPROX_COUNT_DISTINCT function. Without extensions loaded, the only valid value is APPROX_COUNT_DISTINCT_BUILTIN (a HyperLogLog, or HLL, based implementation). If the DataSketches extension is loaded, this can also be APPROX_COUNT_DISTINCT_DS_HLL (alternative HLL implementation) or APPROX_COUNT_DISTINCT_DS_THETA. Theta sketches use significantly more memory than HLL sketches, so you should prefer one of the two HLL implementations.	APPROX_COUNT_DISTINCT_BUILTIN

:::info Previous versions of Druid had properties named druid.sql.planner.maxQueryCount and druid.sql.planner.maxSemiJoinRowsInMemory. These properties are no longer available. Since Druid 0.18.0, you can use druid.server.http.maxSubqueryRows to control the maximum number of rows permitted across all subqueries. :::

Broker caching

You can optionally only configure caching to be enabled on the Broker by setting caching configs here.

Property	Possible Values	Description	Default
druid.broker.cache.useCache	true, false	Enable the cache on the Broker.	false
druid.broker.cache.populateCache	true, false	Populate the cache on the Broker.	false
druid.broker.cache.useResultLevelCache	true, false	Enable result level caching on the Broker.	false
druid.broker.cache.populateResultLevelCache	true, false	Populate the result level cache on the Broker.	false
druid.broker.cache.resultLevelCacheLimit	positive integer	Maximum size of query response that can be cached.	Integer.MAX_VALUE
druid.broker.cache.unCacheable	All druid query types	All query types to not cache.	[]
druid.broker.cache.cacheBulkMergeLimit	positive integer or 0	Queries with more segments than this number will not attempt to fetch from cache at the broker level, leaving potential caching fetches (and cache result merging) to the Historicals	Integer.MAX_VALUE
druid.broker.cache.maxEntrySize	positive integer	Maximum cache entry size in bytes.	1_000_000

See cache configuration for how to configure cache settings.

:::info Note: Even if cache is enabled, for groupBy queries, segment level cache does not work on Brokers. See Query caching for more information. :::

Segment discovery

Property	Possible Values	Description	Default
druid.serverview.type	batch or http	Segment discovery method to use. "http" enables discovering segments using HTTP instead of ZooKeeper.	http
druid.broker.segment.watchedTiers	List of strings	The Broker watches segment announcements from processes that serve segments to build a cache to relate each process to the segments it serves. This configuration allows the Broker to only consider segments being served from a list of tiers. By default, Broker considers all tiers. This can be used to partition your dataSources in specific Historical tiers and configure brokers in partitions so that they are only queryable for specific dataSources. This config is mutually exclusive from druid.broker.segment.ignoredTiers and at most one of these can be configured on a Broker.	none
druid.broker.segment.ignoredTiers	List of strings	The Broker watches segment announcements from processes that serve segments to build a cache to relate each process to the segments it serves. This configuration allows the Broker to ignore the segments being served from a list of tiers. By default, Broker considers all tiers. This config is mutually exclusive from druid.broker.segment.watchedTiers and at most one of these can be configured on a Broker.	none
druid.broker.segment.watchedDataSources	List of strings	Broker watches the segment announcements from processes serving segments to build cache of which process is serving which segments, this configuration allows to only consider segments being served from a whitelist of dataSources. By default, Broker would consider all datasources. This can be used to configure brokers in partitions so that they are only queryable for specific dataSources.	none
druid.broker.segment.watchRealtimeTasks	Boolean	The Broker watches segment announcements from processes that serve segments to build a cache to relate each process to the segments it serves. When watchRealtimeTasks is true, the Broker watches for segment announcements from both Historicals and realtime processes. To configure a broker to exclude segments served by realtime processes, set watchRealtimeTasks to false.	true
druid.broker.segment.awaitInitializationOnStart	Boolean	Whether the Broker will wait for its view of segments to fully initialize before starting up. If set to 'true', the Broker's HTTP server will not start up, and the Broker will not announce itself as available, until the server view is initialized. See also druid.sql.planner.awaitInitializationOnStart, a related setting.	true

Cache configuration

This section describes caching configuration that is common to Broker, Historical, and MiddleManager/Peon processes.

Caching could optionally be enabled on the Broker, Historical, and MiddleManager/Peon processes. See Broker, Historical, and Peon configuration options for how to enable it for different processes.

Druid uses a local in-memory cache by default, unless a different type of cache is specified. Use the druid.cache.type configuration to set a different kind of cache.

Cache settings are set globally, so the same configuration can be re-used for both Broker and Historical processes, when defined in the common properties file.

Cache type

Property	Possible Values	Description	Default
druid.cache.type	local, memcached, hybrid, caffeine	The type of cache to use for queries. See below of the configuration options for each cache type	caffeine

Local cache

:::info DEPRECATED: Use caffeine (default as of v0.12.0) instead :::

The local cache is deprecated in favor of the Caffeine cache, and may be removed in a future version of Druid. The Caffeine cache affords significantly better performance and control over eviction behavior compared to local cache, and is recommended in any situation where you are using JRE 8u60 or higher.

A simple in-memory LRU cache. Local cache resides in JVM heap memory, so if you enable it, make sure you increase heap size accordingly.

Property	Description	Default
druid.cache.sizeInBytes	Maximum cache size in bytes. Zero disables caching.	0
druid.cache.initialSize	Initial size of the hash table backing the cache.	500000
druid.cache.logEvictionCount	If non-zero, log cache eviction every logEvictionCount items.	0

Caffeine cache

A highly performant local cache implementation for Druid based on Caffeine. Requires a JRE8u60 or higher if using COMMON_FJP.

Configuration

The following table shows the configuration options known to this module:

runtime.properties	Description	Default
druid.cache.type	Set this to caffeine or leave out parameter	caffeine
druid.cache.sizeInBytes	The maximum size of the cache in bytes on heap. It can be configured as described in here.	min(1GiB, Runtime.maxMemory / 10)
druid.cache.expireAfter	The time (in ms) after an access for which a cache entry may be expired	None (no time limit)
druid.cache.cacheExecutorFactory	The executor factory to use for Caffeine maintenance. One of COMMON_FJP, SINGLE_THREAD, or SAME_THREAD	ForkJoinPool common pool (COMMON_FJP)
druid.cache.evictOnClose	If a close of a namespace (ex: removing a segment from a process) should cause an eager eviction of associated cache values	false

druid.cache.cacheExecutorFactory

The following are the possible values for druid.cache.cacheExecutorFactory, which controls how maintenance tasks are run:

• COMMON_FJP (default) use the common ForkJoinPool. Should use with JRE 8u60 or higher. Older versions of the JRE may have worse performance than newer JRE versions.
• SINGLE_THREAD Use a single-threaded executor.
• SAME_THREAD Cache maintenance is done eagerly.

Metrics

In addition to the normal cache metrics, the caffeine cache implementation also reports the following in both total and delta:

Metric	Description	Normal value
query/cache/caffeine/*/requests	Count of hits or misses.	hit + miss
query/cache/caffeine/*/loadTime	Length of time caffeine spends loading new values (unused feature).	0
query/cache/caffeine/*/evictionBytes	Size in bytes that have been evicted from the cache	Varies, should tune cache sizeInBytes so that sizeInBytes/evictionBytes is approximately the rate of cache churn you desire.

Memcached

Uses memcached as cache backend. This allows all processes to share the same cache.

Property	Description	Default
druid.cache.expiration	Memcached expiration time.	2592000 (30 days)
druid.cache.timeout	Maximum time in milliseconds to wait for a response from Memcached.	500
druid.cache.hosts	Comma separated list of Memcached hosts <host:port>. Need to specify all nodes when druid.cache.clientMode is set to static. Dynamic mode automatically identifies nodes in your cluster so just specifying the configuration endpoint and port is fine.	none
druid.cache.maxObjectSize	Maximum object size in bytes for a Memcached object.	52428800 (50 MiB)
druid.cache.memcachedPrefix	Key prefix for all keys in Memcached.	druid
druid.cache.numConnections	Number of memcached connections to use.	1
druid.cache.protocol	Memcached communication protocol. Can be binary or text.	binary
druid.cache.locator	Memcached locator. Can be consistent or array_mod.	consistent
druid.cache.enableTls	Enable TLS based connection for Memcached client. Boolean.	false
druid.cache.clientMode	Client Mode. Static mode requires the user to specify individual cluster nodes. Dynamic mode uses AutoDiscovery feature of AWS Memcached. String. "static" or "dynamic"	static
druid.cache.skipTlsHostnameVerification	Skip TLS Hostname Verification. Boolean.	true

Hybrid

Uses a combination of any two caches as a two-level L1 / L2 cache. This may be used to combine a local in-memory cache with a remote memcached cache.

Cache requests will first check L1 cache before checking L2. If there is an L1 miss and L2 hit, it will also populate L1.

Property	Description	Default
druid.cache.l1.type	The type of cache to use for L1 cache. See druid.cache.type configuration for valid types.	caffeine
druid.cache.l2.type	The type of cache to use for L2 cache. See druid.cache.type configuration for valid types.	caffeine
druid.cache.l1.*	Any property valid for the given type of L1 cache can be set using this prefix. For instance, if you are using a caffeine L1 cache, specify druid.cache.l1.sizeInBytes to set its size.	defaults are the same as for the given cache type
druid.cache.l2.*	Prefix for L2 cache settings, see description for L1.	defaults are the same as for the given cache type
druid.cache.useL2	A boolean indicating whether to query L2 cache, if it's a miss in L1. It makes sense to configure this to false on Historical processes, if L2 is a remote cache like memcached, and this cache also used on brokers, because in this case if a query reached Historical it means that a broker didn't find corresponding results in the same remote cache, so a query to the remote cache from Historical is guaranteed to be a miss.	true
druid.cache.populateL2	A boolean indicating whether to put results into L2 cache.	true

General query configuration

This section describes configurations that control behavior of Druid's query types, applicable to Broker, Historical, and MiddleManager processes.

Overriding default query context values

You can override any query context general parameter default value by setting the runtime property in the format of druid.query.default.context.{query_context_key}. The druid.query.default.context.{query_context_key} runtime property prefix applies to all current and future query context keys, the same as how query context parameter passed with the query works. You can override the runtime property value if the value for the same key is specified in the query contexts.

The precedence chain for query context values is as follows:

hard-coded default value in Druid code <- runtime property not prefixed with druid.query.default.context <- runtime property prefixed with druid.query.default.context <- context parameter in the query

Note that not all query context key has a runtime property not prefixed with druid.query.default.context that can override the hard-coded default value. For example, maxQueuedBytes has druid.broker.http.maxQueuedBytes but joinFilterRewriteMaxSize does not. Hence, the only way of overriding joinFilterRewriteMaxSize hard-coded default value is with runtime property druid.query.default.context.joinFilterRewriteMaxSize.

To further elaborate on the previous example:

If neither druid.broker.http.maxQueuedBytes or druid.query.default.context.maxQueuedBytes is set and the query does not have maxQueuedBytes in the context, then the hard-coded value in Druid code is use. If runtime property only contains druid.broker.http.maxQueuedBytes=x and query does not have maxQueuedBytes in the context, then the value of the property, x, is use. However, if query does have maxQueuedBytes in the context, then that value is use instead. If runtime property only contains druid.query.default.context.maxQueuedBytes=y OR runtime property contains both druid.broker.http.maxQueuedBytes=x and druid.query.default.context.maxQueuedBytes=y, then the value of druid.query.default.context.maxQueuedBytes, y, is use (given that query does not have maxQueuedBytes in the context). If query does have maxQueuedBytes in the context, then that value is use instead.

TopN query config

Property	Description	Default
druid.query.topN.minTopNThreshold	See TopN Aliasing for details.	1000

Search query config

Property	Description	Default
druid.query.search.maxSearchLimit	Maximum number of search results to return.	1000
druid.query.search.searchStrategy	Default search query strategy.	useIndexes

SegmentMetadata query config

Property	Description	Default
druid.query.segmentMetadata.defaultHistory	When no interval is specified in the query, use a default interval of defaultHistory before the end time of the most recent segment, specified in ISO8601 format. This property also controls the duration of the default interval used by GET /druid/v2/datasources/{dataSourceName} interactions for retrieving datasource dimensions and metrics.	P1W
druid.query.segmentMetadata.defaultAnalysisTypes	This can be used to set the Default Analysis Types for all segment metadata queries, this can be overridden when making the query	["cardinality", "interval", "minmax"]

GroupBy query config

This section describes the configurations for groupBy queries. You can set the runtime properties in the runtime.properties file on Broker, Historical, and MiddleManager processes. You can set the query context parameters through the query context.

Supported runtime properties:

Property	Description	Default
druid.query.groupBy.maxSelectorDictionarySize	Maximum amount of heap space (approximately) to use for per-segment string dictionaries. See groupBy memory tuning and resource limits for details.	100000000
druid.query.groupBy.maxMergingDictionarySize	Maximum amount of heap space (approximately) to use for per-query string dictionaries. When the dictionary exceeds this size, a spill to disk will be triggered. See groupBy memory tuning and resource limits for details.	100000000
druid.query.groupBy.maxOnDiskStorage	Maximum amount of disk space to use, per-query, for spilling result sets to disk when either the merging buffer or the dictionary fills up. Queries that exceed this limit will fail. Set to zero to disable disk spilling.	0 (disabled)
druid.query.groupBy.defaultOnDiskStorage	Default amount of disk space to use, per-query, for spilling the result sets to disk when either the merging buffer or the dictionary fills up. Set to zero to disable disk spilling for queries which don't override maxOnDiskStorage in their context.	druid.query.groupBy.maxOnDiskStorage

Supported query contexts:

Key	Description
maxSelectorDictionarySize	Can be used to lower the value of druid.query.groupBy.maxMergingDictionarySize for this query.
maxMergingDictionarySize	Can be used to lower the value of druid.query.groupBy.maxMergingDictionarySize for this query.
maxOnDiskStorage	Can be used to set maxOnDiskStorage to a value between 0 and druid.query.groupBy.maxOnDiskStorage for this query. If this query context override exceeds druid.query.groupBy.maxOnDiskStorage, the query will use druid.query.groupBy.maxOnDiskStorage. Omitting this from the query context will cause the query to use druid.query.groupBy.defaultOnDiskStorage for maxOnDiskStorage

Advanced configurations

Supported runtime properties:

Property	Description	Default
druid.query.groupBy.singleThreaded	Merge results using a single thread.	false
druid.query.groupBy.bufferGrouperInitialBuckets	Initial number of buckets in the off-heap hash table used for grouping results. Set to 0 to use a reasonable default (1024).	0
druid.query.groupBy.bufferGrouperMaxLoadFactor	Maximum load factor of the off-heap hash table used for grouping results. When the load factor exceeds this size, the table will be grown or spilled to disk. Set to 0 to use a reasonable default (0.7).	0
druid.query.groupBy.forceHashAggregation	Force to use hash-based aggregation.	false
druid.query.groupBy.intermediateCombineDegree	Number of intermediate processes combined together in the combining tree. Higher degrees will need less threads which might be helpful to improve the query performance by reducing the overhead of too many threads if the server has sufficiently powerful CPU cores.	8
druid.query.groupBy.numParallelCombineThreads	Hint for the number of parallel combining threads. This should be larger than 1 to turn on the parallel combining feature. The actual number of threads used for parallel combining is min(druid.query.groupBy.numParallelCombineThreads, druid.processing.numThreads).	1 (disabled)

Supported query contexts:

Key	Description	Default
groupByIsSingleThreaded	Overrides the value of druid.query.groupBy.singleThreaded for this query.
bufferGrouperInitialBuckets	Overrides the value of druid.query.groupBy.bufferGrouperInitialBuckets for this query.	none
bufferGrouperMaxLoadFactor	Overrides the value of druid.query.groupBy.bufferGrouperMaxLoadFactor for this query.	none
forceHashAggregation	Overrides the value of druid.query.groupBy.forceHashAggregation	none
intermediateCombineDegree	Overrides the value of druid.query.groupBy.intermediateCombineDegree	none
numParallelCombineThreads	Overrides the value of druid.query.groupBy.numParallelCombineThreads	none
sortByDimsFirst	Sort the results first by dimension values and then by timestamp.	false
forceLimitPushDown	When all fields in the orderby are part of the grouping key, the broker will push limit application down to the Historical processes. When the sorting order uses fields that are not in the grouping key, applying this optimization can result in approximate results with unknown accuracy, so this optimization is disabled by default in that case. Enabling this context flag turns on limit push down for limit/orderbys that contain non-grouping key columns.	false

Expression processing configurations

Key	Description	Default
druid.expressions.useStrictBooleans	Controls the behavior of Druid boolean operators and functions, if set to true all boolean values are either 1 or 0. This configuration has been deprecated and will be removed in a future release, taking on the true behavior. See expression documentation for more information.	true
druid.expressions.allowNestedArrays	If enabled, Druid array expressions can create nested arrays. This configuration has been deprecated and will be removed in a future release, taking on the true behavior.	true

Router

Router process configs

Property	Description	Default
druid.host	The host for the current process. This is used to advertise the current processes location as reachable from another process and should generally be specified such that http://${druid.host}/ could actually talk to this process	InetAddress.getLocalHost().getCanonicalHostName()
druid.bindOnHost	Indicating whether the process's internal jetty server bind on druid.host. Default is false, which means binding to all interfaces.	false
druid.plaintextPort	This is the port to actually listen on; unless port mapping is used, this will be the same port as is on druid.host	8888
druid.tlsPort	TLS port for HTTPS connector, if druid.enableTlsPort is set then this config will be used. If druid.host contains port then that port will be ignored. This should be a non-negative Integer.	9088
druid.service	The name of the service. This is used as a dimension when emitting metrics and alerts to differentiate between the various services	druid/router

Runtime configuration

Property	Description	Default
druid.router.defaultBrokerServiceName	The default Broker to connect to in case service discovery fails.	druid/broker
druid.router.tierToBrokerMap	Queries for a certain tier of data are routed to their appropriate Broker. This value should be an ordered JSON map of tiers to Broker names. The priority of Brokers is based on the ordering.	{"_default_tier": "<defaultBrokerServiceName>"}
druid.router.defaultRule	The default rule for all datasources.	_default
druid.router.pollPeriod	How often to poll for new rules.	PT1M
druid.router.sql.enable	Enable routing of SQL queries using strategies. Whentrue, the Router uses the strategies defined in druid.router.strategies to determine the broker service for a given SQL query. When false, the Router uses the defaultBrokerServiceName.	false
druid.router.strategies	Please see Router Strategies for details.	[{"type":"timeBoundary"},{"type":"priority"}]
druid.router.avatica.balancer.type	Class to use for balancing Avatica queries across Brokers. Please see Avatica Query Balancing.	rendezvousHash
druid.router.managementProxy.enabled	Enables the Router's management proxy functionality.	false
druid.router.http.numConnections	Size of connection pool for the Router to connect to Broker processes. If there are more queries than this number that all need to speak to the same process, then they will queue up.	20
druid.router.http.eagerInitialization	Indicates that http connections from Router to Broker should be eagerly initialized. If set to true, numConnections connections are created upon initialization	true
druid.router.http.readTimeout	The timeout for data reads from Broker processes.	PT15M
druid.router.http.numMaxThreads	Maximum number of worker threads to handle HTTP requests and responses	max(10, ((number of cores * 17) / 16 + 2) + 30)
druid.router.http.numRequestsQueued	Maximum number of requests that may be queued to a destination	1024
druid.router.http.requestBuffersize	Size of the content buffer for receiving requests. These buffers are only used for active connections that have requests with bodies that will not fit within the header buffer	8 * 1024