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 process corresponding to the directory (e.g., 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.

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 processes:

1. -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
2. -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.
3. -Djava.io.tmpdir=<a path> Various parts of the system that interact with the file system do it via temporary files, and these files can get somewhat large. Many production systems are set up to have small (but fast) /tmp directories, which can be problematic with Druid so we recommend pointing the JVM’s tmp directory to something with a little more meat. This directory should not be volatile tmpfs. This directory should also have good read and write speed and hence NFS mount should strongly be avoided.
4. -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 process 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 process type. Useful when some useful extension contains some module, which shouldn't be loaded on some Druid process 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 ZK through a set of standard path configurations. We recommend just setting the base ZK path, 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.paths.propertiesPath	Zookeeper properties path.	${druid.zk.paths.base}/properties
druid.zk.paths.announcementsPath	Druid process announcement path.	${druid.zk.paths.base}/announcements
druid.zk.paths.liveSegmentsPath	Current path for where Druid processes announce their segments.	${druid.zk.paths.base}/segments
druid.zk.paths.loadQueuePath	Entries here cause Historical processes to load and drop segments.	${druid.zk.paths.base}/loadQueue
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 processes 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	Middle managers 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

Exhibitor

Exhibitor is a supervisor system for ZooKeeper. Exhibitor can dynamically scale-up/down the cluster of ZooKeeper servers. Druid can update self-owned list of ZooKeeper servers through Exhibitor without restarting. That is, it allows Druid to keep the connections of Exhibitor-supervised ZooKeeper servers.

Property	Description	Default
druid.exhibitor.service.hosts	A JSON array which contains the hostnames of Exhibitor instances. Please specify this property if you want to use Exhibitor-supervised cluster.	none
druid.exhibitor.service.port	The REST port used to connect to Exhibitor.	8080
druid.exhibitor.service.restUriPath	The path of the REST call used to get the server set.	/exhibitor/v1/cluster/list
druid.exhibitor.service.useSsl	Boolean flag for whether or not to use https protocol.	false
druid.exhibitor.service.pollingMs	How often to poll the exhibitors for the list	10000

Note that druid.zk.service.host is used as a backup in case an Exhibitor instance can't be contacted and therefore should still be set.

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 process. Please see Configuration section of individual processes to check the valid and default values for these ports.

Jetty Server TLS Configuration

Druid uses Jetty as an embedded web server. To get familiar with TLS/SSL in general and related concepts like Certificates etc. reading this Jetty documentation might be helpful. To get more in depth knowledge of TLS/SSL support in Java in general, please refer to this guide. The documentation here can help in understanding TLS/SSL configurations listed below. This document lists all the possible values for the below mentioned configs among others provided by Java implementation.

Property	Description	Default	Required
druid.server.https.keyStorePath	The file path or URL of the TLS/SSL Key store.	none	yes
druid.server.https.keyStoreType	The type of the key store.	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 Key Store.	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.authenticationChain.	"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 processes 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 processes that can serve queries can also log the query requests they see. Broker processes can additionally log the SQL requests (both from HTTP and JDBC) they see.

Property	Description	Default
druid.request.logging.type	Choices: noop, file, emitter, slf4j, filtered, composing, switching. How to log every query request.	[required to configure request logging]

Note that, you can enable sending all the HTTP requests to log by setting "org.apache.druid.jetty.RequestLog" to DEBUG level. See Logging

File Request Logging

Daily request logs are stored on disk.

Property	Description	Default
druid.request.logging.dir	Historical, Realtime and Broker processes 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'"

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. 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. Example

2019-01-14T10:00:00.000Z        127.0.0.1       {"sqlQuery/time":100,"sqlQuery/bytes":600,"success":true,"identity":"user1"}  {"query":"SELECT page, COUNT(*) AS Edits FROM wikiticker WHERE __time BETWEEN TIMESTAMP '2015-09-12 00:00:00' AND TIMESTAMP '2015-09-13 00:00:00' 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

Every request is emitted to some external location.

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

SLF4J Request Logging

Every request is logged via SLF4J. Native queries are serialized into JSON in the log message regardless of the SLF4J format specification. They will be logged under the class org.apache.druid.server.log.LoggingRequestLogger.

Property	Description	Default
druid.request.logging.setMDC	If MDC entries should be set in the log entry. Your logging setup still has to be configured to handle MDC to format this data	false
druid.request.logging.setContextMDC	If the druid query context should be added to the MDC entries. Has no effect unless setMDC is true	false

For native query, the following MDC fields are populated with setMDC:

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

Filtered Request Logger filters requests based on a configurable query/time threshold (for native query) and sqlQuery/time threshold (for SQL query). For native query, only request logs where query/time is above the threshold are emitted. For SQL query, only request logs where sqlQuery/time is above the threshold are emitted.

Property	Description	Default
druid.request.logging.queryTimeThresholdMs	Threshold value for query/time in milliseconds.	0, i.e., no filtering
druid.request.logging.sqlQueryTimeThresholdMs	Threshold value for sqlQuery/time 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

Composite Request Logging

Composite 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

Switching Request Logger routes native query's request logs to one request logger and SQL query's request logs to another request logger.

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

Enabling Metrics

Druid processes periodically emit metrics and different metrics monitors can be included. Each process can overwrite the default list of monitors.

Property	Description	Default
druid.monitoring.emissionPeriod	How often metrics are emitted.	PT1M
druid.monitoring.monitors	Sets list of Druid monitors used by a process. See below for names and more information. For example, you can specify monitors for a Broker with druid.monitoring.monitors=["org.apache.druid.java.util.metrics.SysMonitor","org.apache.druid.java.util.metrics.JvmMonitor"].	none (no monitors)

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 processes. 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	This uses the SIGAR library to report on various system activities and statuses.
org.apache.druid.server.metrics.HistoricalMetricsMonitor	Reports statistics on Historical processes.
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.segment.realtime.RealtimeMetricsMonitor	Reports statistics on Realtime processes.
org.apache.druid.server.metrics.EventReceiverFirehoseMonitor	Reports how many events have been queued in the EventReceiverFirehose.
org.apache.druid.server.metrics.QueryCountStatsMonitor	Reports how many queries have been successful/failed/interrupted.
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.

Emitting Metrics

The Druid servers emit various metrics and alerts via something we call an Emitter. There are three emitter implementations included with the code, a "noop" emitter (the default if none is specified), one that just logs to log4j ("logging"), and one that does POSTs of JSON events to a server ("http"). The properties for using the logging emitter are described below.

Property	Description	Default
druid.emitter	Setting this value to "noop", "logging", "http" or "parametrized" will initialize one of the emitter modules. The value "composing" can be used to initialize multiple emitter modules.	noop

Logging Emitter Module

Property	Description	Default
druid.emitter.logging.loggerClass	Choices: HttpPostEmitter, LoggingEmitter, NoopServiceEmitter, ServiceEmitter. The class used for logging.	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, e.g., 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 (5191680 (i. e. 5 MB))
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 5MB)
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

When emitting events to a TLS-enabled receiver, the Http Emitter will by default use an SSLContext obtained via the process described at Druid's internal communication over TLS, i.e., the same SSLContext that would be used for internal communications between Druid processes.

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

druid.emitter.parametrized.httpEmitting.* configs correspond to the configs of Http Emitter Modules, see above. Except recipientBaseUrl. E.g., druid.emitter.parametrized.httpEmitting.flushMillis, druid.emitter.parametrized.httpEmitting.flushCount, druid.emitter.parametrized.httpEmitting.ssl.trustStorePath, etc.

The additional configs are:

Property	Description	Default
druid.emitter.parametrized.recipientBaseUrlPattern	The URL pattern to send an event to, based on the event's feed. E.g., 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, e.g., ["logging","http"].	[]

Graphite Emitter

To use graphite as emitter set druid.emitter=graphite. For configuration details please follow this link.

Metadata storage

These properties specify the JDBC connection and other configuration around the metadata storage. The only processes 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. Choose from "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 which 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_taskLog
druid.metadata.storage.tables.taskLock	Used by the indexing service to store task locks.	druid_taskLock
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, e.g., Coordinator rules.	druid_audit

Deep storage

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

Property	Description	Default
druid.storage.type	Choices:local, noop, s3, hdfs, c*. The type of deep storage to use.	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. Note that the druid-hdfs-storage extension must be loaded.

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. Note that the druid-cassandra-storage extension must be loaded.

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

Task Logging

If you are running the indexing service in remote mode, the task logs must be stored in S3, Azure Blob Store, Google Cloud Storage or HDFS.

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

You can also configure the Overlord to automatically retain the task logs in log directory and entries in task-related metadata storage tables only for last x milliseconds by configuring following additional properties. Caution: Automatic log file deletion typically works based on log file modification timestamp on the backing store, so large clock skews between druid processes and backing store nodes might result in unintended behavior.

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)

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.

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

Property	Description	Default
druid.indexer.logs.container	The Azure Blob Store container to write logs to	none
druid.indexer.logs.prefix	The path to prepend to logs	none

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

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 process. 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 processes to get information about the segments loaded in the cluster.

Property	Description	Default
druid.selectors.coordinator.serviceName	The druid.service name of the Coordinator process. 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.	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

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

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

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	When set to true, null values will be stored as '' for string columns and 0 for numeric columns. Set to false to store and query data in SQL compatible mode.	true

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.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)

Master Server

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

Coordinator

For general Coordinator Process information, see here.

Static Configuration

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

Coordinator Process Config

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	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 ZK 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 process.	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 specified.	true
druid.coordinator.kill.on	Boolean flag for whether or not the Coordinator should submit kill task for unused segments, that is, hard 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. These kill tasks will delete all unused segments except for the last durationToRetain period. Whitelist or All can be set via dynamic configuration killAllDataSources and killDataSourceWhitelist described later.	false
druid.coordinator.kill.period	How often to send kill tasks to the indexing service. Value must be greater than druid.coordinator.period.indexingPeriod. Only applies if kill is turned on.	P1D (1 Day)
druid.coordinator.kill.durationToRetain	Do not kill unused segments in last durationToRetain, must be greater or equal to 0. Only applies and MUST be specified if kill is turned on. Note that default value is invalid.	PT-1S (-1 seconds)
druid.coordinator.kill.maxSegments	Kill at most n unused segments per kill task submission, must be greater than 0. Only applies and MUST be specified if kill is turned on. Note that default value is invalid.	0
druid.coordinator.balancer.strategy	Specify the type of balancing strategy that the coordinator should use to distribute segments among the historicals. cachingCost is logically equivalent to cost but is more CPU-efficient on large clusters and will replace cost in the future versions, users are invited to try it. Use diskNormalized to distribute segments among processes so that the disks fill up uniformly and use random to randomly pick processes to distribute segments.	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. Notes, 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.repeatDelay	The start and repeat delay for the loadqueuepeon, which manages the load and drop of segments.	PT0.050S (50 ms)
druid.coordinator.asOverlord.enabled	Boolean value for whether this Coordinator process should act like an Overlord as well. This configuration allows users to simplify a druid cluster by not having to deploy any standalone Overlord processes. 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. See next.	false
druid.coordinator.asOverlord.overlordService	Required, if druid.coordinator.asOverlord.enabled is true. This must be same value as druid.service on standalone Overlord processes and druid.selectors.indexing.serviceName on Middle Managers.	NULL

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.	batch
druid.coordinator.loadqueuepeon.type	curator or http	Whether to use "http" or "curator" implementation to assign segment loads/drops to historical	curator
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

Additional config when "http" loadqueuepeon is used

Property	Description	Default
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 process.	1

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 configuration to change certain behavior on the fly. The Coordinator uses a JSON spec object from the Druid metadata storage config table. This object is detailed below:

It is recommended that you use the Coordinator Console to configure these parameters. However, if you need to do it via HTTP, the JSON object can be submitted to the Coordinator via a POST request at:

http://<COORDINATOR_IP>:<PORT>/druid/coordinator/v1/config

Optional Header Parameters for auditing the config change can also be specified.

Header Param Name	Description	Default
X-Druid-Author	author making the config change	""
X-Druid-Comment	comment describing the change being done	""

A sample Coordinator dynamic config JSON object is shown below:

{
  "millisToWaitBeforeDeleting": 900000,
  "mergeBytesLimit": 100000000,
  "mergeSegmentsLimit" : 1000,
  "maxSegmentsToMove": 5,
  "replicantLifetime": 15,
  "replicationThrottleLimit": 10,
  "emitBalancingStats": false,
  "killDataSourceWhitelist": ["wikipedia", "testDatasource"],
  "decommissioningNodes": ["localhost:8182", "localhost:8282"],
  "decommissioningMaxPercentOfMaxSegmentsToMove": 70,
  "pauseCoordinator": false
}

Issuing a GET request at the same URL will return the spec that is currently in place. A description of the config setup spec is shown below.

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
maxSegmentsToMove	The maximum number of segments that can be moved at any given time.	5
replicantLifetime	The maximum number of Coordinator runs for a segment to be replicated before we start alerting.	15
replicationThrottleLimit	The maximum number of segments that can be replicated at one time.	10
balancerComputeThreads	Thread pool size for computing moving cost of segments in segment balancing. Consider increasing this if you have a lot of segments and moving segments starts to get stuck.	1
emitBalancingStats	Boolean flag for whether or not we should emit balancing stats. This is an expensive operation.	false
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
killAllDataSources	Send kill tasks for ALL dataSources if property druid.coordinator.kill.on is true. If this is set to true then killDataSourceWhitelist must not be specified or be empty list.	false
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 that could be queued for loading to any given server. This parameter could be used to speed up segments loading process, especially if there are "slow" nodes in the cluster (with low loading speed) or if too much segments scheduled to be replicated to some particular node (faster loading could be preferred to better segments distribution). Desired value depends on segments loading speed, acceptable replication time and number of nodes. Value 1000 could be a start point for a rather big cluster. Default value is 0 (loading queue is unbounded)	0
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 decommissioningMaxPercentOfMaxSegmentsToMove.	none
decommissioningMaxPercentOfMaxSegmentsToMove	The maximum number of segments that may be moved away from 'decommissioning' servers to non-decommissioning (that is, active) servers during one Coordinator run. This value is relative to the total maximum segment movements allowed during one run which is determined by maxSegmentsToMove. If decommissioningMaxPercentOfMaxSegmentsToMove is 0, segments will neither be moved from or to 'decommissioning' servers, effectively putting them in a sort of "maintenance" mode that will not participate in balancing or assignment by load rules. Decommissioning can also become stalled if there are no available active servers to place the segments. By leveraging the maximum percent of decommissioning segment movements, an operator can prevent active servers from overload by prioritizing balancing, or decrease decommissioning time instead. The value should be between 0 and 100.	70
pauseCoordinator	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, Emission of metrics controlled by the dynamic coordinator config emitBalancingStats, 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

To view the audit history of Coordinator dynamic config issue a GET request to the URL -

http://<COORDINATOR_IP>:<PORT>/druid/coordinator/v1/config/history?interval=<interval>

default value of interval can be specified by setting druid.audit.manager.auditHistoryMillis (1 week if not configured) in Coordinator runtime.properties

To view last entries of the audit history of Coordinator dynamic config issue a GET request to the URL -

http://<COORDINATOR_IP>:<PORT>/druid/coordinator/v1/config/history?count=<n>

Lookups Dynamic Configuration

These configuration options control the behavior of the Lookup dynamic configuration described in the lookups page

Property	Description	Default
druid.manager.lookups.hostDeleteTimeout	How long to wait for a DELETE request to a particular process before considering the DELETE a failure	PT1S
druid.manager.lookups.hostUpdateTimeout	How long to wait for a POST request to a particular process 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 processes 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	How many milliseconds between checks for configuration changes	30_000

Compaction Dynamic Configuration

Compaction configurations can also be set or updated dynamically using Coordinator's API without restarting Coordinators.

For details about segment compaction, please check Segment Size Optimization.

A description of the compaction config is:

Property	Description	Required
dataSource	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. Because each compaction task runs with a single thread, setting this value too far above 1–2GB will result in compaction tasks taking an excessive amount of time.	no (default = 419430400)
maxRowsPerSegment	Max number of rows per segment after compaction.	no
skipOffsetFromLatest	The offset for searching segments to be compacted. Strongly recommended to set for realtime dataSources.	no (default = "P1D")
tuningConfig	Tuning config for compaction tasks. See below Compaction Task TuningConfig.	no
taskContext	Task context for compaction tasks.	no

An example of compaction config is:

{
  "dataSource": "wikiticker"
}

Note that compaction tasks can fail if their locks are revoked by other tasks of higher priorities. Since realtime tasks have a higher priority than compaction task by default, it can be problematic if there are frequent conflicts between compaction tasks and realtime tasks. If this is the case, the coordinator's automatic compaction might get stuck because of frequent compaction task failures. This kind of problem may happen especially in Kafka/Kinesis indexing systems which allow late data arrival. If you see this problem, it's recommended to set skipOffsetFromLatest to some large enough value to avoid such conflicts between compaction tasks and realtime tasks.

Compaction TuningConfig

Property	Description	Required
maxRowsInMemory	See tuningConfig for indexTask	no (default = 1000000)
maxBytesInMemory	See tuningConfig for indexTask	no (1/6 of max JVM memory)
maxTotalRows	See tuningConfig for indexTask	no (default = 20000000)
splitHintSpec	See tuningConfig for indexTask	no (default = null)
indexSpec	See IndexSpec	no
maxPendingPersists	See tuningConfig for indexTask	no (default = 0 (meaning one persist can be running concurrently with ingestion, and none can be queued up))
pushTimeout	See tuningConfig for indexTask	no (default = 0)
maxNumConcurrentSubTasks	See tuningConfig for indexTask	no (default = 1)

Overlord

For general Overlord Process information, see here.

Overlord Static Configuration

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

Overlord 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	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	Choices "local" or "remote". Indicates whether tasks should be run locally or in a distributed environment. Experimental task runner "httpRemote" is also available which is same as "remote" but uses HTTP to interact with Middle Managers instead of Zookeeper.	local
druid.indexer.storage.type	Choices are "local" or "metadata". Indicates whether incoming tasks should be stored locally (in heap) or in metadata storage. Storing incoming tasks in metadata storage allows for tasks to be resumed if the Overlord should fail.	local
druid.indexer.storage.recentlyFinishedThreshold	A duration of time to store task results.	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.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 after e.g. 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

The following configs only apply if the Overlord is running in remote mode. For a description of local vs. remote mode, please see (../design/overlord.html).

Property	Description	Default
druid.indexer.runner.taskAssignmentTimeout	How long to wait after a task as been assigned to a MiddleManager before throwing an error.	PT5M
druid.indexer.runner.minWorkerVersion	The minimum MiddleManager version to send tasks to.	"0"
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.	524288
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

There are additional configs for autoscaling (if it is enabled):

Property	Description	Default
druid.indexer.autoscale.strategy	Choices are "noop", "ec2" or "gce". Sets the strategy to run when autoscaling is required.	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

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)

Overlord Dynamic Configuration

The Overlord can dynamically change worker behavior.

The JSON object can be submitted to the Overlord via a POST request at:

http://<OVERLORD_IP>:<port>/druid/indexer/v1/worker

Optional Header Parameters for auditing the config change can also be specified.

Header Param Name	Description	Default
X-Druid-Author	author making the config change	""
X-Druid-Comment	comment describing the change being done	""

A sample worker config spec is shown below:

{
  "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
      }
    }
  }
}

Issuing a GET request at the same URL will return the current worker config spec that is currently in place. The worker config spec list above is just a sample for EC2 and it is possible to extend the code base for other deployment environments. A description of the worker config spec is shown below.

Property	Description	Default
selectStrategy	How to assign tasks to MiddleManagers. Choices are fillCapacity, equalDistribution, and javascript.	equalDistribution
autoScaler	Only used if autoscaling is enabled. See below.	null

To view the audit history of worker config issue a GET request to the URL -

http://<OVERLORD_IP>:<port>/druid/indexer/v1/worker/history?interval=<interval>

default value of interval can be specified by setting druid.audit.manager.auditHistoryMillis (1 week if not configured) in Overlord runtime.properties.

To view last entries of the audit history of worker config issue a GET request to the URL -

http://<OVERLORD_IP>:<port>/druid/indexer/v1/worker/history?count=<n>

Worker Select Strategy

Worker select strategies control how Druid assigns tasks to MiddleManagers.

Equal Distribution

Tasks are assigned to the MiddleManager with the most free slots at the time the task begins running. This is useful if you want work evenly distributed across your MiddleManagers.

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

Equal Distribution With Category Spec

This strategy is a variant of Equal Distribution, which support workerCategorySpec field rather than affinityConfig. By specifying workerCategorySpec, you can assign tasks to run on different categories of MiddleManagers based on the tasks' taskType and dataSource name. This strategy can't work with AutoScaler since the behavior is undefined.

Property	Description	Default
type	equalDistributionWithCategorySpec.	required; must be equalDistributionWithCategorySpec
workerCategorySpec	Worker Category Spec object	null (no worker category spec)

Example: specify tasks default to run on c1 whose task type is "index_kafka", while dataSource "ds1" run on c2.

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

Fill Capacity

Tasks are assigned to the worker with the most currently-running tasks at the time the task begins running. This is useful in situations where you are elastically auto-scaling MiddleManagers, since it will tend 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	Affinity config object	null (no affinity)

Fill Capacity With Category Spec

This strategy is a variant of Fill Capacity, which support workerCategorySpec field rather than affinityConfig. The usage is the same with equalDistributionWithCategorySpec strategy. This strategy can't work with AutoScaler since the behavior is undefined.

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

Before using the equalDistributionWithCategorySpec and fillCapacityWithCategorySpec strategies, you must upgrade overlord and all MiddleManagers to the version that support this feature.

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

Example: 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}"
}

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.

Affinity

Affinity configs can be provided to the equalDistribution and fillCapacity strategies using the "affinityConfig" field. If not provided, the default is to not use affinity at all.

Property	Description	Default
affinity	JSON object mapping a datasource String name to a list of indexing service MiddleManager host:port String 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	With weak affinity (the default), tasks for a dataSource may be assigned to other MiddleManagers if their affinity-mapped MiddleManagers are not able to run all pending tasks in the queue for that dataSource. With strong affinity, tasks for a dataSource will only ever be assigned to their affinity-mapped MiddleManagers, and will wait in the pending queue if necessary.	false

WorkerCategorySpec

WorkerCategorySpec can be provided 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
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
availabilityZone	What availability zone to run in.	none
nodeData	A JSON object that describes how to launch new nodes.	none; required
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 processes that reside on Data servers (MiddleManagers/Peons and Historicals) in the suggested three-server configuration.

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

MiddleManager and Peons

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

MiddleManager Process Config

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.	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

Middle managers 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 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.	524288
druid.indexer.runner.startPort	Starting port used for peon processes, should be greater than 1023 and less than 65536.	8100
druid.indexer.runner.endPort	Ending port used for peon processes, 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 processes. If provided and non-empty, ports for peon processes 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.	0
druid.worker.capacity	Maximum number of tasks the MiddleManager can accept.	Number of CPUs on the machine - 1
druid.worker.category	A string to name the category that the MiddleManager node belongs to.	__default_worker_category

Peon Processing

Processing properties set on the Middlemanager will be passed through to Peons.

Property	Description	Default
druid.processing.buffer.sizeBytes	This specifies a buffer size 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.	auto (max 1GB)
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 v2) 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.columnCache.sizeBytes	Maximum size in bytes for the dimension value lookup cache. Any value greater than 0 enables the cache. It is currently disabled by default. Enabling the lookup cache can significantly improve the performance of aggregators operating on dimension values, such as the JavaScript aggregator, or cardinality aggregator, but can slow things down if the cache hit rate is low (i.e. dimensions with few repeating values). Enabling it may also require additional garbage collection tuning to avoid long GC pauses.	0 (disabled)
druid.processing.fifo	If the processing queue should treat tasks of equal priority in a FIFO manner	false
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> 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	Choices are "local" and "remote". Setting this to local means you intend to run the peon as a standalone process (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:2.8.5
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.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. Currently three types of medium exist for those buffers: temporary files, off-heap memory, and on-heap memory.

Temporary files (tmpFile) are stored under the task working directory (see druid.indexer.task.baseTaskDir configuration above) and thus share it's mounting properties, e. g. 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 medium (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 medium (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 could be configured per-task (see Tasks page, "TuningConfig" section), but if it's not specified for a task, or it's not supported for a particular task type, then the value from the configuration below is used:

Property	Description	Default
druid.peon.defaultSegmentWriteOutMediumFactory.type	tmpFile, offHeapMemory, or onHeapMemory, see explanation above	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.globalIngestionHeapLimitBytes	Total amount of heap available for ingestion processing. This is applied by automatically setting the maxBytesInMemory property on tasks.	60% of configured JVM heap
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:2.8.5
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.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.	PT0S (do not wait)
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.	[]

Indexer Processing Resources

Property	Description	Default
druid.processing.buffer.sizeBytes	This specifies a buffer size 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.	auto (max 1GB)
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 v2) 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.columnCache.sizeBytes	Maximum size in bytes for the dimension value lookup cache. Any value greater than 0 enables the cache. It is currently disabled by default. Enabling the lookup cache can significantly improve the performance of aggregators operating on dimension values, such as the JavaScript aggregator, or cardinality aggregator, but can slow things down if the cache hit rate is low (i.e. dimensions with few repeating values). Enabling it may also require additional garbage collection tuning to avoid long GC pauses.	0 (disabled)
druid.processing.fifo	If the processing queue should treat tasks of equal priority in a FIFO manner	false
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 Process information, see here.

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

Historical 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	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 process wants assigned to it. This is not a limit that Historical processes actually enforces, just a value published to the Coordinator process so it can plan accordingly.	0
druid.server.tier	A string to name the distribution tier that the storage process belongs to. Many of the rules Coordinator processes 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 processes 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 process are first stored on the local file system (in a disk cache) and then served by the Historical process. 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": 10000, "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.locationSelectorStrategy	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 process is no longer serving a segment.	true
druid.segmentCache.dropSegmentDelayMillis	How long a process delays before completely dropping segment.	30000 (30 seconds)
druid.segmentCache.infoDir	Historical processes keep track of the segments they are serving so that when the process 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. One catch is that if historical crashes while in the process of downloading and creating segment files, it is possible to end up with a corrupted segment on disk, this requires manual intervention to delete corrupted files. When the flag is set to true, historical startup would complete successfully and queries using this segment would fail at runtime.	false
druid.coordinator.loadqueuepeon.curator.numCallbackThreads	Number of threads for executing callback actions associated with loading or dropping of segments. One might want to increase this number when noticing clusters are lagging behind w.r.t. balancing segments across historical nodes.	2

In druid.segmentCache.locations, freeSpacePercent was added because 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 process 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.locationSelectorStrategy, 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.	PT0S (do not wait)
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

Processing

Property	Description	Default
druid.processing.buffer.sizeBytes	This specifies a buffer size 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.	auto (max 1GB)
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 v2) 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.columnCache.sizeBytes	Maximum size in bytes for the dimension value lookup cache. Any value greater than 0 enables the cache. It is currently disabled by default. Enabling the lookup cache can significantly improve the performance of aggregators operating on dimension values, such as the JavaScript aggregator, or cardinality aggregator, but can slow things down if the cache hit rate is low (i.e. dimensions with few repeating values). Enabling it may also require additional garbage collection tuning to avoid long GC pauses.	0 (disabled)
druid.processing.fifo	If the processing queue should treat tasks of equal priority in a FIFO manner	false
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	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 processes 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. E.g., [-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 HTTP threads to dedicate to query processing. To save HTTP thread capacity, this should be lower than druid.server.http.numThreads, but it is worth noting that like druid.server.http.enableRequestLimit is set that query requests over this limit will be denied instead of waiting in the Jetty HTTP request queue.	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 none.

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

'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, and 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.	Long.MAX_VALUE
druid.server.http.maxSubqueryRows	Maximum number of rows from subqueries per query. These rows are stored in memory.	100000
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.	PT0S (do not wait)
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

Client Configuration

Druid Brokers use an HTTP client to communicate with 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.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 the channel to the data server. Similar to druid.server.http.maxScatterGatherBytes, except unlike that configuration, this one will trigger backpressure rather than query failure. Zero means disabled. Can be overridden by the "maxQueuedBytes" query context parameter.	0 (disabled)
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 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.	auto (max 1GB)
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 v2) 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.columnCache.sizeBytes	Maximum size in bytes for the dimension value lookup cache. Any value greater than 0 enables the cache. It is currently disabled by default. Enabling the lookup cache can significantly improve the performance of aggregators operating on dimension values, such as the JavaScript aggregator, or cardinality aggregator, but can slow things down if the cache hit rate is low (i.e. dimensions with few repeating values). Enabling it may also require additional garbage collection tuning to avoid long GC pauses.	0 (disabled)
druid.processing.fifo	If the processing queue should treat tasks of equal priority in a FIFO manner	false
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 + 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.

Broker query configuration

See general query configuration.

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 number of rows to return in a single JDBC frame. Setting this property to -1 indicates that no row limit should be applied. Clients can optionally specify a row limit in their requests; if a client specifies a row limit, the lesser value of the client-provided limit and maxRowsPerFrame will be used.	5,000
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.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.useApproximateCountDistinct	Whether to use an approximate cardinality algorithm for COUNT(DISTINCT foo).	true
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

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.

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.	batch
druid.broker.segment.watchedTiers	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 tiers. By default, Broker would consider 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.	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.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

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 hashtable 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

Below are 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.	min(1GB, 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

Here 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>.	none
druid.cache.maxObjectSize	Maximum object size in bytes for a Memcached object.	52428800 (50 MB)
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

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	type of cache to use for L1 cache. See druid.cache.type configuration for valid types.	caffeine
druid.cache.l2.type	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.

Query vectorization config

The following configurations are to set the default behavior for query vectorization.

Property	Description	Default
druid.query.vectorize	See Vectorization parameters for details. This value can be overridden by vectorize in the query contexts.	true
druid.query.vectorSize	See Vectorization parameters for details. This value can be overridden by vectorSize in the query contexts.	512

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/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.

Configurations for groupBy v2

Supported runtime properties:

Property	Description	Default
druid.query.groupBy.maxMergingDictionarySize	Maximum amount of heap space (approximately) to use for the string dictionary during merging. When the dictionary exceeds this size, a spill to disk will be triggered.	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)

Supported query contexts:

Key	Description
maxMergingDictionarySize	Can be used to lower the value of druid.query.groupBy.maxMergingDictionarySize for this query.
maxOnDiskStorage	Can be used to lower the value of druid.query.groupBy.maxOnDiskStorage for this query.

Advanced configurations

Common configurations for all groupBy strategies

Supported runtime properties:

Property	Description	Default
druid.query.groupBy.defaultStrategy	Default groupBy query strategy.	v2
druid.query.groupBy.singleThreaded	Merge results using a single thread.	false

Supported query contexts:

Key	Description
groupByStrategy	Overrides the value of druid.query.groupBy.defaultStrategy for this query.
groupByIsSingleThreaded	Overrides the value of druid.query.groupBy.singleThreaded for this query.

GroupBy v2 configurations

Supported runtime properties:

Property	Description	Default
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
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

GroupBy v1 configurations

Supported runtime properties:

Property	Description	Default
druid.query.groupBy.maxIntermediateRows	Maximum number of intermediate rows for the per-segment grouping engine. This is a tuning parameter that does not impose a hard limit; rather, it potentially shifts merging work from the per-segment engine to the overall merging index. Queries that exceed this limit will not fail.	50000
druid.query.groupBy.maxResults	Maximum number of results. Queries that exceed this limit will fail.	500000

Supported query contexts:

Key	Description	Default
maxIntermediateRows	Can be used to lower the value of druid.query.groupBy.maxIntermediateRows for this query.	None
maxResults	Can be used to lower the value of druid.query.groupBy.maxResults for this query.	None
useOffheap	Set to true to store aggregations off-heap when merging results.	false

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": ""}
druid.router.defaultRule	The default rule for all datasources.	"_default"
druid.router.pollPeriod	How often to poll for new rules.	PT1M
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.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