You should have the Java JDK and ZooKeeper ensemble installed before starting the deployment of the Storm cluster.

Perform the following steps to install the Java SDK 7 on your machine. You can also go with JDK 1.8:

1. Download the Java SDK 7 RPM from Oracle's site (http://www.oracle.com/technetwork/java/javase/downloads/index.html).
2. Install the Java jdk-7u<version>-linux-x64.rpm file on your CentOS machine using the following command:

sudo rpm -ivh jdk-7u<version>-linux-x64.rpm 

3. Add the following environment variable in the ~/.bashrc file:

export JAVA_HOME=/usr/java/jdk<version>

4. Add the path of the bin directory of the JDK to the PATH system environment variable...

In this chapter, we will learn how to set up a three nodes Storm cluster, of which one node will be the active master node (Nimbus) and the other two will be worker nodes (supervisors).

The following is the deployment diagram of our three node Storm cluster:

The following are the steps that need to be performed to set up a three node Storm cluster:

1. Install and run the ZooKeeper cluster. The steps for installing ZooKeeper are mentioned in the previous section.
2. Download the latest stable Storm release from https://storm.apache.org/downloads.html; at the time of writing, the latest version is Storm 1.0.2.

3. Once you have downloaded the latest version, copy and unzip it in all three machines. Now, we will set the $STORM_HOME environment variable on each machine to make the setup easier. The $STORM_HOME environment contains the path of the Storm...

Before starting the development, you should have Eclipse and Maven installed in your project. The sample topology explained here will cover how to create a basic Storm project, including a spout and bolt, and how to build, and execute them.

Create a Maven project by using com.stormadvance as groupId and storm-example as artifactId.

Add the following Maven dependencies to the pom.xml file:

<dependency> 
  <groupId>org.apache.storm</groupId> 
  <artifactId>storm-core</artifactId> 
  <version>1.0.2</version> 
  <scope>provided<scope> 
</dependency> 

Add the following Maven build plugins in the pom.xml file:

<build> 
  <plugins> 
    <plugin...

This section covers the following operations that a user can perform on the Storm cluster:

• Deactivate
• Activate
• Rebalance
• Kill
• Dynamic log level settings

Storm supports the deactivating a topology. In the deactivated state, spouts will not emit any new tuples into the pipeline, but the processing of the already emitted tuples will continue. The following is the command to deactivate the running topology:

$> bin/storm deactivate topologyName 

Deactivate SampleStormClusterTopology using the following command:

bin/storm deactivate SampleStormClusterTopology 

The following information is displayed:

0 [main] INFO backtype.storm.thrift - Connecting to Nimbus at...

This section will show you how we can start the Storm UI daemon. However, before starting the Storm UI daemon, we assume that you have a running Storm cluster. The Storm cluster deployment steps are mentioned in the previous sections of this chapter. Now, go to the Storm home directory (cd $STORM_HOME) at the leader Nimbus machine and run the following command to start the Storm UI daemon:

$> cd $STORM_HOME
$> bin/storm ui &  

By default, the Storm UI starts on the 8080 port of the machine where it is started. Now, we will browse to the http://nimbus-node:8080 page to view the Storm UI, where Nimbus node is the IP address or hostname of the the Nimbus machine.

The following is a screenshot of the Storm home page:

The dynamic log level allows us to change the log level setting of the topology on the runtime from the Storm CLI and the Storm UI.

Go through the following steps to update the log level from the Storm UI:

1. Deploy SampleStormClusterTopology again on the Storm cluster if it is not running.
2. Browse the Storm UI at http://nimbus-node:8080/.
3. Click on the storm_example topology.

4. Now click on the Change Log Level button to change the ROOT logger of the topology, as shown in the following are the screenshots:

5. Configure the entries mentioned in the following screenshots change the ROOT logger to ERROR:

6. If you are planning to...

In this chapter, we have covered the installation of Storm and ZooKeeper clusters, the deployment of topologies on Storm clusters, the high availability of Nimbus nodes, and topology monitoring through the Storm UI. We have also covered the different operations a user can perform on running topology. Finally, we focused on how we can change the log level of running topology.

In the next chapter, we will focus on the distribution of topologies on multiple Storm machines/nodes.