druid/docs/content/configuration/index.md

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Configuring Druid

This describes the common configuration shared by all Druid nodes. These configurations can be defined in the common.runtime.properties file.

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.
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.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.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

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

Zookeeper Behavior

Property	Description	Default
druid.zk.service.sessionTimeoutMs	ZooKeeper session timeout, in milliseconds.	30000
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 node announcement path.	${druid.zk.paths.base}/announcements
druid.zk.paths.liveSegmentsPath	Current path for where Druid nodes announce their segments.	${druid.zk.paths.base}/segments
druid.zk.paths.loadQueuePath	Entries here cause historical nodes 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 nodes 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 middle managers.	${druid.zk.paths.indexer.base}/tasks
druid.zk.paths.indexer.statusPath	Parent path for announcement of task statuses.	${druid.zk.paths.indexer.base}/status
druid.zk.paths.indexer.leaderLatchPath	Used for Overlord leader election.	${druid.zk.paths.indexer.base}/leaderLatchPath

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 ofter 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.

Startup Logging

All nodes 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 nodes that can serve queries can also log the query requests they see.

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

Note that, you can enable sending all the HTTP requests to log by setting "io.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 nodes maintain request logs of all of the requests they get (interacton 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

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. Queries are serialized into JSON in the log message regardless of the SJF4J format specification. They will be logged under the class io.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

MDC fields populated with setMDC:

MDC field	Description
queryId	The query ID
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. Only request logs where query/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.delegate	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

Enabling Metrics

Druid nodes periodically emit metrics and different metrics monitors can be included. Each node 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 node. See below for names and more information. For example, you can specify monitors for a Broker with druid.monitoring.monitors=["com.metamx.metrics.SysMonitor","com.metamx.metrics.JvmMonitor"].	none (no monitors)

The following monitors are available:

Name	Description
io.druid.client.cache.CacheMonitor	Emits metrics (to logs) about the segment results cache for Historical and Broker nodes. Reports typical cache statistics include hits, misses, rates, and size (bytes and number of entries), as well as timeouts and and errors.
com.metamx.metrics.SysMonitor	This uses the SIGAR library to report on various system activities and statuses. Make sure to add the sigar library jar to your classpath if using this monitor.
io.druid.server.metrics.HistoricalMetricsMonitor	Reports statistics on Historical nodes.
com.metamx.metrics.JvmMonitor	Reports JVM-related statistics.
io.druid.segment.realtime.RealtimeMetricsMonitor	Reports statistics on Realtime nodes.
io.druid.server.metrics.EventReceiverFirehoseMonitor	Reports how many events have been queued in the EventReceiverFirehose.
io.druid.server.metrics.QueryCountStatsMonitor	Reports how many queries have been successful/failed/interrupted.

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, one that just logs to log4j ("logging", which is used by default if no emitter is specified) 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", or "http" will initialize one of the emitter modules. 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.timeOut	The timeout for data reads.	PT5M
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.recipientBaseUrl	The base URL to emit messages to. Druid will POST JSON to be consumed at the HTTP endpoint specified by this property.	none

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, Indexing service and Realtime Nodes.

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.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

Password Provider

Environment variable password provider provides password by looking at specified environment variable. Use this in order to avoid specifying password in runtime.properties file. e.g

{ 
    "type": "environment",
    "variable": "METADATA_STORAGE_PASSWORD"   
}

The values are described below.

Field	Type	Description	Required
type	String	password provider type	Yes: environment
variable	String	environment variable to read password from	Yes

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.

Property	Description	Default
druid.s3.accessKey	The access key to use to access S3.	none
druid.s3.secretKey	The secret key to use to access S3.	none
druid.storage.bucket	S3 bucket name.	none
druid.storage.baseKey	S3 object key prefix for storage.	none
druid.storage.disableAcl	Boolean flag for ACL.	false
druid.storage.archiveBucket	S3 bucket name for archiving when running the indexing-service archive task.	none
druid.storage.archiveBaseKey	S3 object key prefix for archiving.	none

HDFS Deep Storage

This deep storage is used to interface with HDFS.

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.

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

Caching

You can enable caching of results at the broker, historical, or realtime level using following configurations.

Property	Description	Default
druid.cache.type	local, memcached	The type of cache to use for queries.
druid.(broker|historical|realtime).cache.unCacheable	All druid query types	All query types to not cache.
druid.(broker|historical|realtime).cache.useCache	Whether to use cache for getting query results.	false
druid.(broker|historical|realtime).cache.populateCache	Whether to populate cache.	false

Local Cache

Property	Description	Default
druid.cache.sizeInBytes	Maximum cache size in bytes. You must set this if you enabled populateCache/useCache, or else cache size of zero wouldn't really cache anything.	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

Memcache

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

Indexing Service Discovery

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

Property	Description	Default
druid.selectors.indexing.serviceName	The druid.service name of the indexing service Overlord node. 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 nodes to get information about the segments loaded in the cluster.

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