Table of Contents

Configuration Reference

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

Table of Contents

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       tranquility

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

conf/tranquility:
kafka.json  server.json

Each directory has a runtime.properties file containing configuration properties for the specific Druid service correponding 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

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.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.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. "io.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 node type. Useful when some useful extension contains some module, which shouldn't be loaded on some Druid node 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

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

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.

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 node. Please see Configuration section of individual nodes 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)

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.authenticationChain 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.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 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=["io.druid.java.util.metrics.SysMonitor","io.druid.java.util.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.
io.druid.java.util.metrics.SysMonitor This uses the SIGAR library to report on various system activities and statuses.
io.druid.server.metrics.HistoricalMetricsMonitor Reports statistics on Historical nodes.
io.druid.java.util.metrics.JvmMonitor Reports various JVM-related statistics.
io.druid.java.util.metrics.JvmCpuMonitor Reports statistics of CPU consumption by the JVM.
io.druid.java.util.metrics.CpuAcctDeltaMonitor Reports consumed CPU as per the cpuacct cgroup.
io.druid.java.util.metrics.JvmThreadsMonitor Reports Thread statistics in the JVM, like numbers of total, daemon, started, died threads.
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.
io.druid.server.emitter.HttpEmitterMonitor 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/druid-io/druid/pull/4973.

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", "http" or "parametrized" 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.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 Login and password for authentification in "login:password" form, e. g. druid.emitter.http.basicAuthentication=admin:adminpassword not specified = no authentification
`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

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, 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, 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

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.

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. 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 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 nodes and backing store nodes might result in un-intended behavior.

Property Description Default
druid.indexer.logs.kill.enabled Boolean value for whether to enable deletion of old task logs. false
druid.indexer.logs.kill.durationToRetain Required if kill is enabled. In milliseconds, task logs 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

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

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.

Double Column storage

Druid's storage layer uses a 32-bit float representation to store columns created by the doubleSum, doubleMin, and doubleMax aggregators at indexing time. To instead use 64-bit floats for these columns, please set the system-wide property druid.indexing.doubleStorage=double. This will become the default behavior in a future version of Druid.

Property Description Default
druid.indexing.doubleStorage Set to "double" to use 64-bit double representation for double columns. float

Coordinator

For general Coordinator Node information, see here.

Static Configuration

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

Node Config

Property Description Default
druid.host The host for the current node. This is used to advertise the current processes location as reachable from another node and should generally be specified such that http://${druid.host}/ could actually talk to this process InetAddress.getLocalHost().getCanonicalHostName()
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’s operates by maintaining the current state of the world in memory and periodically looking at the set of segments available 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 indexing tasks to the indexing service. Only applies if merge or conversion is turned on. 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.merge.on Boolean flag for whether or not the coordinator should try and merge small segments into a more optimal segment size. false
druid.coordinator.conversion.on Boolean flag for converting old segment indexing versions to the latest segment indexing version. false
druid.coordinator.load.timeout The timeout duration for when the coordinator assigns a segment to a historical node. 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 earlist 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. false
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 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 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 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 nodes so that the disks fill up uniformly and use random to randomly pick nodes to distribute segments. cost
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 node should act like an overlord as well. This configuration allows users to simplify a druid cluster by not having to deploy any standalone overlord nodes. 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 nodes and druid.selectors.indexing.serviceName on Middle Managers. NULL

Segment Management

Property Possible Values Description Default
druid.announcer.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
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 node. 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.defaultTier The default tier from which default rules will be loaded from. _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 behaviour 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"]
}

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 active before it can start removing (marking unused) segments 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
emitBalancingStats Boolean flag for whether or not we should emit balancing stats. This is an expensive operation. false
killDataSourceWhitelist List of dataSources for which kill tasks are sent if property druid.coordinator.kill.on is true. This can be a list of comma-separated dataSources 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 dataSources for which pendingSegments are NOT cleaned up if property druid.coordinator.kill.pendingSegments.on is true. This can be a list of comma-separated dataSources 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

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 (EXPERIMENTAL)

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 node before considering the DELETE a failure PT1s
druid.manager.lookups.hostUpdateTimeout How long to wait for a POST request to a particular node 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 nodes 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

Overlord

Overlord Static Configuration

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

Overlord Node Configs

Property Description Default
druid.host The host for the current node. This is used to advertise the current processes location as reachable from another node and should generally be specified such that http://${druid.host}/ could actually talk to this process InetAddress.getLocalHost().getCanonicalHostName()
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 Operation

Property Description Default
druid.indexer.runner.type Choices "local" or "remote". Indicates whether tasks should be run locally or in a distributed environment. 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.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/indexing-service.html#overlord-node).

Property Description Default
druid.indexer.runner.taskAssignmentTimeout How long to wait after a task as been assigned to a middle manager before throwing an error. PT5M
druid.indexer.runner.minWorkerVersion The minimum middle manager version to send tasks to. "0"
druid.indexer.runner.compressZnodes Indicates whether or not the overlord should expect middle managers 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 middle manager is disconnected from Zookeeper. PT15M
druid.indexer.runner.taskShutdownLinkTimeout How long to wait on a shutdown request to a middle manager 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 middle manager 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" or "ec2". 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 middle managers should be added. PT1M
druid.indexer.autoscale.terminatePeriod How often to check when middle managers 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 middle manager 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 middle managers will run on. 8080

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 middle managers. 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 available capacity 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)
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)
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(\"10.0.0.1\");\nbatch_workers.add(\"10.0.0.2\");\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

Autoscaler

Amazon's EC2 is currently the only supported autoscaler.

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

MiddleManager and Peons

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

MiddleManager Node Config

Property Description Default
druid.host The host for the current node. This is used to advertise the current processes location as reachable from another node and should generally be specified such that http://${druid.host}/ could actually talk to this process InetAddress.getLocalHost().getCanonicalHostName()
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 middle manager 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", "io.druid", "user.timezone", "file.encoding", "java.io.tmpdir", "hadoop"
druid.indexer.runner.compressZnodes Indicates whether or not the middle managers 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. 8100
druid.indexer.runner.tlsStartPort Starting TLS port for peon processes, should be greater than 1023. 8300
druid.indexer.runner.separateIngestionEndpoint Deprecated. Use separate server and consequently separate jetty thread pool for ingesting events. Not supported with TLS. false
druid.worker.ip The IP of the worker. localhost
druid.worker.version Version identifier for the middle manager. 0
druid.worker.capacity Maximum number of tasks the middle manager can accept. Number of available processors - 1

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 nodes 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. 1073741824 (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 nodes 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. ["groupBy", "select"]

See cache configuration for how to configure cache settings.

Additional Peon Configuration

Although peons inherit the configurations of their parent middle managers, explicit child peon configs in middle manager 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 node (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/tasks
druid.indexer.task.defaultHadoopCoordinates Hadoop version to use with HadoopIndexTasks that do not request a particular version. org.apache.hadoop:hadoop-client:2.3.0
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 deprecated druid.indexer.runner.separateIngestionEndpoint property is set to true then following configurations are available for the ingestion server at peon:

Property Description Default
druid.indexer.server.chathandler.http.numThreads Deprecated. Number of threads for HTTP requests. Math.max(10, (Number of available processors * 17) / 16 + 2) + 30
druid.indexer.server.chathandler.http.maxIdleTime Deprecated. The Jetty max idle time for a connection. PT5m

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 pre-processed data in some buffers. Currently two types of medium exist for those buffers: temporary files and off-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 properies, 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.

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 tmpFile or offHeapMemory, see explanation above tmpFile

Broker

For general Broker Node information, see here.

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

Broker Node Configs

Property Description Default
druid.host The host for the current node. This is used to advertise the current processes location as reachable from another node and should generally be specified such that http://${druid.host}/ could actually talk to this process InetAddress.getLocalHost().getCanonicalHostName()
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 Prioritization

Property Possible Values Description Default
druid.broker.balancer.type random, connectionCount Determines how the broker balances connections to historical nodes. random choose randomly, connectionCount picks the node 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. Select servers in tiers with a custom priority list. None

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.maxScatterGatherBytes Maximum number of bytes gathered from data nodes such as historicals and realtime processes to execute a query. 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.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 node, 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 and real-time processes. PT15M
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

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. And, optionally, Long-interval queries (of any type) can be broken into shorter interval queries and processed in parallel inside this thread pool. For more details, see "chunkPeriod" in Query Context doc.

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 nodes 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. 1073741824 (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 nodes 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.

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. false
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. 50
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. 100,000
druid.sql.avatica.maxStatementsPerConnection Maximum number of simultaneous open statements per Avatica client connection. 1
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.maxQueryCount Maximum number of queries to issue, including nested queries. Set to 1 to disable sub-queries, or set to 0 for unlimited. 8
druid.sql.planner.maxSemiJoinRowsInMemory Maximum number of rows to keep in memory for executing two-stage semi-join queries like SELECT * FROM Employee WHERE DeptName IN (SELECT DeptName FROM Dept). 100000
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.selectPageSize Page size threshold for Select queries. Select queries for larger resultsets will be issued back-to-back using pagination. 1000
druid.sql.planner.useApproximateCountDistinct Whether to use an approximate cardinalty 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.useFallback Whether to evaluate operations on the broker when they cannot be expressed as Druid queries. This option is not recommended for production since it can generate unscalable query plans. If false, SQL queries that cannot be translated to Druid queries will fail. false

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.unCacheable All druid query types All query types to not cache. ["groupBy", "select"]
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

See cache configuration for how to configure cache settings.

Segment Discovery

Property Possible Values Description Default
druid.announcer.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 nodes serving segments to build cache of which node 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 nodes serving segments to build cache of which node 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

Historical

For general Historical Node information, see here.

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

Historical Node Configuration

Property Description Default
druid.host The host for the current node. This is used to advertise the current processes location as reachable from another node and should generally be specified such that http://${druid.host}/ could actually talk to this process InetAddress.getLocalHost().getCanonicalHostName()
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 node wants assigned to it. This is not a limit that Historical nodes actually enforces, just a value published to the Coordinator node so it can plan accordingly. 0
druid.server.tier A string to name the distribution tier that the storage node belongs to. Many of the rules Coordinator nodes 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 nodes 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 node are first stored on the local file system (in a disk cache) and then served by the Historical node. 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.deleteOnRemove Delete segment files from cache once a node is no longer serving a segment. true
druid.segmentCache.dropSegmentDelayMillis How long a node delays before completely dropping segment. 30000 (30 seconds)
druid.segmentCache.infoDir Historical nodes 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 from deep storage. 10
druid.segmentCache.numBootstrapThreads How many segments to load concurrently from local storage at startup. Same as numLoadingThreads

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.

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.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 nodes 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. 1073741824 (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 nodes 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. ["groupBy", "select"]

See cache configuration for how to configure cache settings.

Cache Configuration

This section describes caching configuration that is common to broker, historical, and middleManager/peon nodes.

Caching can optionally be enabled on the broker, historical, and realtime processing. See broker, historical, and realtime
configuration options for how to enable it for different processes.

Druid uses a local in-memory cache by default, unless a diffrent 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 nodes, 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. None (unlimited)
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 node) 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 nodes 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

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 nodes, 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 middle manager nodes.

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

Segment Metadata 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 nodes. 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 nodes 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 nodes. 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

Realtime nodes

Configuration for the deprecated realtime node can be found here.