Table of Contents API documentation

For general Indexing Service information, see here.

Runtime Configuration

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

Must be set on Overlord and Middle Manager

Node Configs

Property Description Default 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://${}/ could actually talk to this process InetAddress.getLocalHost().getCanonicalHostName()
druid.port This is the port to actually listen on; unless port mapping is used, this will be the same port as is on 8090
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

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 Local filesystem path. log
S3 Task Logs

Store task logs in S3.

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: 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: 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.

Property Description Default The directory to store logs. none

Overlord Configs

Property Description Default
druid.indexer.runner.type Choices "local" or "remote". Indicates whether tasks should be run locally or in a distributed environment. local 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 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:

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

Dynamic Configuration

The overlord can dynamically change worker behavior.

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


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": "fillCapacityWithAffinity",
    "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, fillCapacityWithAffinity, equalDistribution, equalDistributionWithAffinity 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 -


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

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


Worker Select Strategy

Fill Capacity

Workers are assigned tasks until capacity.

Property Description Default
type fillCapacity. required; must be fillCapacity

Note that, if druid.indexer.runner.pendingTasksRunnerNumThreads is set to n (> 1) then it means to fill n workers upto capacity simultaneously and then moving on.

Fill Capacity With Affinity

An affinity config can be provided.

Property Description Default
type fillCapacityWithAffinity. required; must be fillCapacityWithAffinity
affinity JSON object mapping a datasource String name to a list of indexing service middle manager host:port String values. Druid doesn't perform DNS resolution, so the 'host' value must match what is configured on the middle manager and what the middle manager announces itself as (examine the Overlord logs to see what your middle manager announces itself as). {}

Tasks will try to be assigned to preferred workers. Fill capacity strategy is used if no preference for a datasource specified.

Note that, if druid.indexer.runner.pendingTasksRunnerNumThreads is set to n (> 1) then it means to fill n preferred workers upto capacity simultaneously and then moving on.

Equal Distribution

The workers with the least amount of tasks is assigned the task.

Property Description Default
type equalDistribution. required; must be equalDistribution
Equal Distribution With Affinity

An affinity config can be provided.

Property Description Default
type equalDistributionWithAffinity. required; must be equalDistributionWithAffinity
affinity Exactly same with fillCapacityWithAffinity 's affinity. {}

Tasks will try to be assigned to preferred workers. Equal Distribution strategy is used if no preference for a datasource specified.


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 and and all other tasks to other available workers.

"function":"function (config, zkWorkers, task) {\nvar batch_workers = new java.util.ArrayList();\nbatch_workers.add(\"\");\nbatch_workers.add(\"\");\nworkers = zkWorkers.keySet().toArray();\nvar sortedWorkers = new Array()\n;for(var i = 0; i < workers.length; i++){\n sortedWorkers[i] = workers[i];\n}\,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.


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 Configs

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"
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 The port that peons begin running on. 8100
druid.indexer.runner.separateIngestionEndpoint Deprecated. Use separate server and consequently separate jetty thread pool for ingesting events 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 Configs

Although peons inherit the configurations of their parent middle managers, explicit child peon configs in middle manager can be set by prefixing them with:

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("")
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