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Coordinator Node Configuration
==============================
For general Coordinator Node information, see [here](../design/coordinator.html).

Runtime Configuration
---------------------

The coordinator node uses several of the global configs in [Configuration](../configuration/index.html) 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](../operations/tls-support.html) 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.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](#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](../dependencies/metadata-storage.html) 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:

```json
{
  "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|
|--------|-----------|-------|
|`balancerComputeThreads`|The number of threads used in a coordinator balancing run.|1|
|`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](../ingestion/tasks.html).|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 <n> 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](../querying/lookups.html)

|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](../design/coordinator.html#compacting-segments).

A description of the compaction config is:

|Property|Description|Required|
|--------|-----------|--------|
|`dataSource`|dataSource name to be compacted.|yes|
|`taskPriority`|[Priority](../ingestion/tasks.html#task-priorities) 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](#compact-task-tuningconfig).|no|
|`taskContext`|[Task context](../ingestion/tasks.html#task-context) for compact tasks.|no|

An example of compaction config is:

```json
{
  "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.