README.markdown

Example Storm Topologies

Learn to use Storm!


Table of Contents


Getting started

Prerequisites

First, you need java and git installed and in your user's PATH. Also, two of the examples in storm-starter require Python and Ruby.

Next, make sure you have the storm-starter code available on your machine. Git/GitHub beginners may want to use the following command to download the latest storm-starter code and change to the new directory that contains the downloaded code.

$ git clone git://github.com/apache/storm.git && cd storm/examples/storm-starter

storm-starter overview

storm-starter contains a variety of examples of using Storm. If this is your first time working with Storm, check out these topologies first:

  1. ExclamationTopology: Basic topology written in all Java
  2. WordCountTopology: Basic topology that makes use of multilang by implementing one bolt in Python
  3. ReachTopology: Example of complex DRPC on top of Storm

After you have familiarized yourself with these topologies, take a look at the other topopologies in src/jvm/org/apache/storm/starter/ such as RollingTopWords for more advanced implementations.

If you want to learn more about how Storm works, please head over to the Storm project page.

Using storm-starter with Maven

Install Maven

Install Maven (preferably version 3.x) by following the Maven installation instructions.

Build and install Storm jars locally

If you are using the latest development version of Storm, e.g. by having cloned the Storm git repository, then you must first perform a local build of Storm itself. Otherwise you will run into Maven errors such as "Could not resolve dependencies for project org.apache.storm:storm-starter:<storm-version>-SNAPSHOT".

# Must be run from the top-level directory of the Storm code repository
$ mvn clean install -DskipTests=true

This command will build Storm locally and install its jar files to your user's $HOME/.m2/repository/. When you run the Maven command to build and run storm-starter (see below), Maven will then be able to find the corresponding version of Storm in this local Maven repository at $HOME/.m2/repository.

Packaging storm-starter for use on a Storm cluster

You can package a jar suitable for submitting to a Storm cluster with the command:

$ mvn package

This will package your code and all the non-Storm dependencies into a single "uberjar" (or "fat jar") at the path target/storm-starter-{version}.jar.

Example filename of the uberjar:

>>> target/storm-starter-0.9.3-incubating-SNAPSHOT.jar

You can submit (run) a topology contained in this uberjar to Storm via the storm CLI tool:

# Example 1: Run the ExclamationTopology in local mode (LocalCluster)
$ storm jar target/storm-starter-*.jar org.apache.storm.starter.ExclamationTopology

# Example 2: Run the RollingTopWords in remote/cluster mode,
#            under the name "production-topology"
$ storm jar target/storm-starter-*.jar org.apache.storm.starter.RollingTopWords production-topology remote

With submitting you can run topologies which use multilang, for example, WordCountTopology.

Submitting a topology in local vs. remote mode: It depends on the actual code of a topology how you can or even must tell Storm whether to run the topology locally (in an in-memory LocalCluster instance of Storm) or remotely (in a "real" Storm cluster). In the case of RollingTopWords, for instance, this can be done by passing command line arguments. Topologies other than RollingTopWords -- such as ExclamationTopology -- may behave differently, e.g. by always submitting to a remote cluster (i.e. hardcoded in a way that you, as a user, cannot change without modifying the topology code), or by requiring a customized configuration file that the topology code will parse prior submitting the topology to Storm. Similarly, further options such as the name of the topology may be user-configurable or be hardcoded into the topology code. So make sure you understand how the topology of your choice is set up and configured!

Running unit tests

Use the following Maven command to run the unit tests that ship with storm-starter. Unfortunately lein test does not yet run the included unit tests.

$ mvn test

Using storm-starter with IntelliJ IDEA

Importing storm-starter as a project in IDEA

The following instructions will import storm-starter as a new project in IntelliJ IDEA.

  • Open File > Import Project... and navigate to the storm-starter directory of your storm clone (e.g. ~/git/storm/examples/storm-starter).
  • Select Import project from external model, select "Maven", and click Next.
  • In the following screen, enable the checkbox Import Maven projects automatically. Leave all other values at their defaults. Click Next.
  • Make sure to select the intellij profile in the profiles screen. This is important for making sure dependencies set correctly.
  • Click Next on the following screen about selecting Maven projects to import.
  • Select the JDK to be used by IDEA for storm-starter, then click Next.
    • At the time of this writing you should use JDK 7 and above.
    • It is strongly recommended to use Oracle JDK rather than OpenJDK.
  • You may now optionally change the name of the project in IDEA. The default name suggested by IDEA is "storm-starter". Click Finish once you are done.