druid/docs/content/configuration/coordinator.md

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Coordinator Node Configuration

For general Coordinator Node information, see here.

Runtime Configuration

The coordinator node uses several of the global configs in Configuration and has the following set of configurations as well:

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 compact/merge/conversion tasks to the indexing service. It's recommended to be longer than druid.manager.segments.pollDuration	PT1800S (30 mins)
druid.coordinator.startDelay	The operation of the Coordinator works on the assumption that it has an up-to-date view of the state of the world when it runs, the current ZK interaction code, however, is written in a way that doesn’t allow the Coordinator to know for a fact that it’s done loading the current state of the world. This delay is a hack to give it enough time to believe that it has all the data.	PT300S
druid.coordinator.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.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.	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
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 Config (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

Compaction Configuration

Compaction configurations can also be set or updated dynamically without restarting coordinators. For segment compaction, please see Compacting Segments.

A description of the compaction config is:

Property	Description	Required
dataSource	dataSource name to be compacted.	yes
taskPriority	Priority of compact task.	no (default = 25)
targetCompactionSizeBytes	The target segment size of compaction. The actual size of a compact segment might be slightly larger or smaller than this value.	no (default = 838860800)
numTargetCompactionSegments	Max number of segments to compact together.	no (default = 150)
skipOffsetFromLatest	The offset for searching segments to be compacted. Strongly recommended to set for realtime dataSources.	no (default = "P1D")
tuningConfig	Tuning config for compact tasks. See below Compact Task TuningConfig.	no
taskContext	Task context for compact tasks.	no

An example of compaction config is:

{
  "dataSource": "wikiticker",
  "targetCompactionSizeBytes": 800000000,
  "skipOffsetFromLatest": "P1D"
}

For realtime dataSources, it's recommended to set skipOffsetFromLatest to some sufficiently large values to avoid frequent compact task failures.