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druid/docs/content/tutorials/cluster.md

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Clustering

Druid is designed to be deployed as a scalable, fault-tolerant cluster.

In this document, we'll set up a simple cluster and discuss how it can be further configured to meet your needs. This simple cluster will feature scalable, fault-tolerant servers for Historicals and MiddleManagers, and a single coordination server to host the Coordinator and Overlord processes. In production, we recommend deploying Coordinators and Overlords in a fault-tolerant configuration as well.

Select hardware

The Coordinator and Overlord processes can be co-located on a single server that is responsible for handling the metadata and coordination needs of your cluster. The equivalent of an AWS m3.xlarge is sufficient for most clusters. This hardware offers:

  • 4 vCPUs
  • 15 GB RAM
  • 80 GB SSD storage

Historicals and MiddleManagers can be colocated on a single server to handle the actual data in your cluster. These servers benefit greatly from CPU, RAM, and SSDs. The equivalent of an AWS r3.2xlarge is a good starting point. This hardware offers:

  • 8 vCPUs
  • 61 GB RAM
  • 160 GB SSD storage

Druid Brokers accept queries and farm them out to the rest of the cluster. They also optionally maintain an in-memory query cache. These servers benefit greatly from CPU and RAM, and can also be deployed on the equivalent of an AWS r3.2xlarge. This hardware offers:

  • 8 vCPUs
  • 61 GB RAM
  • 160 GB SSD storage

You can consider co-locating any open source UIs or query libraries on the same server that the Broker is running on.

Very large clusters should consider selecting larger servers.

Select OS

We recommend running your favorite Linux distribution. You will also need:

  • Java 8 or better

Your OS package manager should be able to help for both Java. If your Ubuntu-based OS does not have a recent enough version of Java, WebUpd8 offers packages for those OSes.

Download the distribution

First, download and unpack the release archive. It's best to do this on a single machine at first, since you will be editing the configurations and then copying the modified distribution out to all of your servers.

curl -O http://static.druid.io/artifacts/releases/druid-#{DRUIDVERSION}-bin.tar.gz
tar -xzf druid-#{DRUIDVERSION}-bin.tar.gz
cd druid-#{DRUIDVERSION}

In this package, you'll find:

  • LICENSE - the license files.
  • bin/ - scripts related to the single-machine quickstart.
  • conf/* - template configurations for a clustered setup.
  • conf-quickstart/* - configurations for the single-machine quickstart.
  • extensions/* - all Druid extensions.
  • hadoop-dependencies/* - Druid Hadoop dependencies.
  • lib/* - all included software packages for core Druid.
  • quickstart/* - files related to the single-machine quickstart.

We'll be editing the files in conf/ in order to get things running.

Configure deep storage

Druid relies on a distributed filesystem or large object (blob) store for data storage. The most commonly used deep storage implementations are S3 (popular for those on AWS) and HDFS (popular if you already have a Hadoop deployment).

S3

In conf/druid/_common/common.runtime.properties,

  • Set druid.extensions.loadList=["druid-s3-extensions"].

  • Comment out the configurations for local storage under "Deep Storage" and "Indexing service logs".

  • Uncomment and configure appropriate values in the "For S3" sections of "Deep Storage" and "Indexing service logs".

After this, you should have made the following changes:

druid.extensions.loadList=["druid-s3-extensions"]

#druid.storage.type=local
#druid.storage.storageDirectory=var/druid/segments

druid.storage.type=s3
druid.storage.bucket=your-bucket
druid.storage.baseKey=druid/segments
druid.s3.accessKey=...
druid.s3.secretKey=...

#druid.indexer.logs.type=file
#druid.indexer.logs.directory=var/druid/indexing-logs

druid.indexer.logs.type=s3
druid.indexer.logs.s3Bucket=your-bucket
druid.indexer.logs.s3Prefix=druid/indexing-logs

HDFS

In conf/druid/_common/common.runtime.properties,

  • Set druid.extensions.loadList=["druid-hdfs-storage"].

  • Comment out the configurations for local storage under "Deep Storage" and "Indexing service logs".

  • Uncomment and configure appropriate values in the "For HDFS" sections of "Deep Storage" and "Indexing service logs".

After this, you should have made the following changes:

druid.extensions.loadList=["druid-hdfs-storage"]

#druid.storage.type=local
#druid.storage.storageDirectory=var/druid/segments

druid.storage.type=hdfs
druid.storage.storageDirectory=/druid/segments

#druid.indexer.logs.type=file
#druid.indexer.logs.directory=var/druid/indexing-logs

druid.indexer.logs.type=hdfs
druid.indexer.logs.directory=/druid/indexing-logs

Also,

  • Place your Hadoop configuration XMLs (core-site.xml, hdfs-site.xml, yarn-site.xml, mapred-site.xml) on the classpath of your Druid nodes. You can do this by copying them into conf/druid/_common/.

Configure Tranquility Server (optional)

Data streams can be sent to Druid through a simple HTTP API powered by Tranquility Server. If you will be using this functionality, then at this point you should configure Tranquility Server.

Configure Tranquility Kafka (optional)

Druid can consuming streams from Kafka through Tranquility Kafka. If you will be using this functionality, then at this point you should configure Tranquility Kafka.

Configure for connecting to Hadoop (optional)

If you will be loading data from a Hadoop cluster, then at this point you should configure Druid to be aware of your cluster:

  • Update druid.indexer.task.hadoopWorkingPath in conf/middleManager/runtime.properties to a path on HDFS that you'd like to use for temporary files required during the indexing process. druid.indexer.task.hadoopWorkingPath=/tmp/druid-indexing is a common choice.

  • Place your Hadoop configuration XMLs (core-site.xml, hdfs-site.xml, yarn-site.xml, mapred-site.xml) on the classpath of your Druid nodes. You can do this by copying them into conf/druid/_common/core-site.xml, conf/druid/_common/hdfs-site.xml, and so on.

Note that you don't need to use HDFS deep storage in order to load data from Hadoop. For example, if your cluster is running on Amazon Web Services, we recommend using S3 for deep storage even if you are loading data using Hadoop or Elastic MapReduce.

For more info, please see batch ingestion.

Configure addresses for Druid coordination

In this simple cluster, you will deploy a single Druid Coordinator, a single Druid Overlord, a single ZooKeeper instance, and an embedded Derby metadata store on the same server.

In conf/druid/_common/common.runtime.properties, replace "zk.service.host" with the address of the machine that runs your ZK instance:

  • druid.zk.service.host

In conf/druid/_common/common.runtime.properties, replace "metadata.storage.*" with the address of the machine that you will use as your metadata store:

  • druid.metadata.storage.connector.connectURI
  • druid.metadata.storage.connector.host
In production, we recommend running 2 servers, each running a Druid Coordinator and a Druid Overlord. We also recommend running a ZooKeeper cluster on its own dedicated hardware, as well as replicated metadata storage such as MySQL or PostgreSQL, on its own dedicated hardware.

Tune Druid processes that serve queries

Druid Historicals and MiddleManagers can be co-located on the same hardware. Both Druid processes benefit greatly from being tuned to the hardware they run on. If you are running Tranquility Server or Kafka, you can also colocate Tranquility with these two Druid processes. If you are using r3.2xlarge EC2 instances, or similar hardware, the configuration in the distribution is a reasonable starting point.

If you are using different hardware, we recommend adjusting configurations for your specific hardware. The most commonly adjusted configurations are:

  • -Xmx and -Xms
  • druid.server.http.numThreads
  • druid.processing.buffer.sizeBytes
  • druid.processing.numThreads
  • druid.query.groupBy.maxIntermediateRows
  • druid.query.groupBy.maxResults
  • druid.server.maxSize and druid.segmentCache.locations on Historical Nodes
  • druid.worker.capacity on MiddleManagers
Keep -XX:MaxDirectMemory >= numThreads*sizeBytes, otherwise Druid will fail to start up..

Please see the Druid configuration documentation for a full description of all possible configuration options.

Tune Druid Brokers

Druid Brokers also benefit greatly from being tuned to the hardware they run on. If you are using r3.2xlarge EC2 instances, or similar hardware, the configuration in the distribution is a reasonable starting point.

If you are using different hardware, we recommend adjusting configurations for your specific hardware. The most commonly adjusted configurations are:

  • -Xmx and -Xms
  • druid.server.http.numThreads
  • druid.cache.sizeInBytes
  • druid.processing.buffer.sizeBytes
  • druid.processing.numThreads
  • druid.query.groupBy.maxIntermediateRows
  • druid.query.groupBy.maxResults
Keep -XX:MaxDirectMemory >= numThreads*sizeBytes, otherwise Druid will fail to start up.

Please see the Druid configuration documentation for a full description of all possible configuration options.

Open ports (if using a firewall)

If you're using a firewall or some other system that only allows traffic on specific ports, allow inbound connections on the following:

  • 1527 (Derby on your Coordinator; not needed if you are using a separate metadata store like MySQL or PostgreSQL)
  • 2181 (ZooKeeper; not needed if you are using a separate ZooKeeper cluster)
  • 8081 (Coordinator)
  • 8082 (Broker)
  • 8083 (Historical)
  • 8084 (Standalone Realtime, if used)
  • 8088 (Router, if used)
  • 8090 (Overlord)
  • 8091, 8100–8199 (Druid Middle Manager; you may need higher than port 8199 if you have a very high druid.worker.capacity)
  • 8200 (Tranquility Server, if used)
In production, we recommend deploying ZooKeeper and your metadata store on their own dedicated hardware, rather than on the Coordinator server.

Start Coordinator, Overlord, Zookeeper, and metadata store

Copy the Druid distribution and your edited configurations to your coordination server. If you have been editing the configurations on your local machine, you can use rsync to copy them:

rsync -az druid-#{DRUIDVERSION}/ COORDINATION_SERVER:druid-#{DRUIDVERSION}/

Log on to your coordination server and install Zookeeper:

curl http://www.gtlib.gatech.edu/pub/apache/zookeeper/zookeeper-3.4.11/zookeeper-3.4.11.tar.gz -o zookeeper-3.4.11.tar.gz
tar -xzf zookeeper-3.4.11.tar.gz
cd zookeeper-3.4.11
cp conf/zoo_sample.cfg conf/zoo.cfg
./bin/zkServer.sh start
In production, we also recommend running a ZooKeeper cluster on its own dedicated hardware.

On your coordination server, cd into the distribution and start up the coordination services (you should do this in different windows or pipe the log to a file):

java `cat conf/druid/coordinator/jvm.config | xargs` -cp conf/druid/_common:conf/druid/coordinator:lib/* io.druid.cli.Main server coordinator
java `cat conf/druid/overlord/jvm.config | xargs` -cp conf/druid/_common:conf/druid/overlord:lib/* io.druid.cli.Main server overlord

You should see a log message printed out for each service that starts up. You can view detailed logs for any service by looking in the var/log/druid directory using another terminal.

Start Historicals and MiddleManagers

Copy the Druid distribution and your edited configurations to your servers set aside for the Druid Historicals and MiddleManagers.

On each one, cd into the distribution and run this command to start a Data server:

java `cat conf/druid/historical/jvm.config | xargs` -cp conf/druid/_common:conf/druid/historical:lib/* io.druid.cli.Main server historical
java `cat conf/druid/middleManager/jvm.config | xargs` -cp conf/druid/_common:conf/druid/middleManager:lib/* io.druid.cli.Main server middleManager

You can add more servers with Druid Historicals and MiddleManagers as needed.

For clusters with complex resource allocation needs, you can break apart Historicals and MiddleManagers and scale the components individually. This also allows you take advantage of Druid's built-in MiddleManager autoscaling facility.

If you are doing push-based stream ingestion with Kafka or over HTTP, you can also start Tranquility Server on the same hardware that holds MiddleManagers and Historicals. For large scale production, MiddleManagers and Tranquility Server can still be co-located. If you are running Tranquility (not server) with a stream processor, you can co-locate Tranquility with the stream processor and not require Tranquility Server.

curl -O http://static.druid.io/tranquility/releases/tranquility-distribution-0.8.0.tgz
tar -xzf tranquility-distribution-0.8.0.tgz
cd tranquility-distribution-0.8.0
bin/tranquility <server or kafka> -configFile <path_to_druid_distro>/conf/tranquility/<server or kafka>.json

Start Druid Broker

Copy the Druid distribution and your edited configurations to your servers set aside for the Druid Brokers.

On each one, cd into the distribution and run this command to start a Broker (you may want to pipe the output to a log file):

java `cat conf/druid/broker/jvm.config | xargs` -cp conf/druid/_common:conf/druid/broker:lib/* io.druid.cli.Main server broker

You can add more Brokers as needed based on query load.

Loading data

Congratulations, you now have a Druid cluster! The next step is to learn about recommended ways to load data into Druid based on your use case. Read more about loading data.