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Booting a Druid Cluster

Loading Your Data and All About Queries contain recipes to boot a small druid cluster on localhost. However, when it's time to run a more realistic setup—for production or just for testing production—you'll want to find a way to start the cluster on multiple hosts. This document describes two different ways to do this: manually, or as a cloud service via Apache Whirr.

Manually Booting a Druid Cluster

You can provision individual servers, loading Druid onto each machine (or building it) and setting the required configuration for each type of node. You'll also have to set up required external dependencies. Then you'll have to start each node. This process is outlined in Tutorial: The Druid Cluster.

Apache Whirr

Apache Whirr is a set of libraries for launching cloud services. For Druid, Whirr serves as an easy way to launch a cluster in Amazon AWS by using simple commands and configuration files (called recipes).

NOTE: Whirr will install Druid 0.6.115 (an older version of Druid). Also, it doesn't work with JDK1.7.0_55. JDK1.7.0_45 recommended.

You'll need an AWS account, S3 Bucket and an EC2 key pair from that account so that Whirr can connect to the cloud via the EC2 API. If you haven't generated a key pair, see the AWS documentation or see this Whirr FAQ.

Install Whirr

Clone the code from https://github.com/druid-io/whirr and build Whirr:

git clone git@github.com:druid-io/whirr.git
cd whirr
git checkout trunk
mvn clean install -Dmaven.test.failure.ignore=true

In order to run the test below, you'll also need two files that available only from a standard install of Druid or the Druid repo:

  • druid/examples/bin/examples/wikipedia/wikipedia_realtime.spec
  • druid/examples/bin/examples/indexing/wikipedia_realtime_task.json

Configure Whirr

The Whirr recipe for Druid is the configuration file $WHIRR_HOME/recipies/druid.properties. You can edit this file to suit your needs; it is annotated and self-explanatory. Here are some hints about that file:

  • Set whirr.location-id to a specific AWS region if desired. If this is left blank, a region is chosen for you. The default value is us-east-1.
  • You can choose the hardware used with whirr.hardware-id to a specific instance type (e.g., m1.large). By default druid.properties, m3.2xlarge (broker, historical, middle manager), m1.xlarge (coordinator, overlord), and m1.small (zookeeper, mysql) are used.
  • If you don't choose an image via whirr.image-id (image must be compatible with hardware), you'll get plain vanilla Linux. Default druid.properties uses ami-018c9568 (Ubuntu 12.04).
  • SSH keys (not password protected) must exist for the local user. If they are in the default locations, ${sys:user.home}/.ssh/id_rsa and ${sys:user.home}/.ssh/id_rsa.pub, Whirr will find them. Otherwise, you'll have to specify them with whirr.private-key-file and whirr.public-key-file.
  • Two Druid cluster templates (see whirr.instance-templates) are provided: a small cluster running on a single EC2 instance, and a larger cluster running on multiple instances.
  • You must specify the path to an S3 bucket. Otherwise the cluster won't be able to process tasks.
  • To successfully submit the test task below, you'll need to specify the location of the wikipedia_realtime.spec in the property whirr.druid.realtime.spec.path.
  • Specify Druid version only if Druid extenions are being used.

The following AWS information must be set in druid.properties, as environment variables, or in the file $WHIRR_HOME/conf/credentials:

PROVIDER=aws-ec2
IDENTITY=<aws-id-key>
CREDENTIAL=<aws-private-key>

How to get the IDENTITY and CREDENTIAL keys is discussed above.

In order to configure each node, you can edit services/druid/src/main/resources/functions/start_druid.sh for JVM configuration and services/druid/src/main/resources/functions/configure_[NODE_NAME].sh for specific node configuration. For more information on configuration, see the Druid configuration documentation.

Start a Test Cluster With Whirr

Run the following command:

% $WHIRR_HOME/bin/whirr launch-cluster --config $WHIRR_HOME/recipes/druid.properties

If Whirr starts without any errors, you should see the following message:

Running on provider aws-ec2 using identity <your-aws-id-here>

You can then use the EC2 dashboard to locate the instances and confirm that they have started up.

If both the instances and the Druid cluster launch successfully, a few minutes later other messages to STDOUT should follow with information returned from EC2, including the instance ID:

Started cluster of 8 instances
Cluster{instances=[Instance{roles=[zookeeper, druid-mysql, druid-coordinator, druid-broker, druid-historical, druid-realtime], publicIp= ...

The final message will contain login information for the instances.

Note that Whirr will return an exception if any of the nodes fail to launch, and the cluster will be destroyed. To destroy the cluster manually, run the following command:

% $WHIRR_HOME/bin/whirr destroy-cluster --config $WHIRR_HOME/recipes/druid.properties

Testing the Cluster

Now you can run an indexing task and a simple query to see if all the nodes have launched correctly. We are going to use a Wikipedia example again. For a realtime indexing task, run the following command:

curl -X 'POST' -H 'Content-Type:application/json' -d @#{PATH_TO}/wikipedia_realtime_task.json #{OVERLORD_PUBLIC_IP_ADDR}:#{PORT}/druid/indexer/v1/task

where OVERLORD_PUBLIC_IP_ADDR should be available from the EC2 information logged to STDOUT, the Overlord port is 8090 by default, and wikipedia_realtime_task.json is discussed above.

Issuing this request should return a task ID.

To check the state of the overlord, open up your browser and go to #{OVERLORD_PUBLIC_IP_ADDR}:#{PORT}/console.html.

Next, go to #{COORDINATOR_PUBLIC_IP_ADDR}:#{PORT}. Click "View Information about the Cluster"->"Full Cluster View." You should now see the information about servers and segments. If the cluster runs correctly, Segment dimensions and Segment binaryVersion fields should be filled up. Allow few minutes for the segments to be processed.

Now you should be able to query the data using broker's public IP address.