Monday, October 22, 2012

Configuring Cassandra JDBC with JBoss AS 7

1. Build the driver source

cassandra-jdbc is not yet available in the public Maven repos so it has to be built from source. There is already an open ticket requesting that the artifacts get published to a public Maven repo. If you do not already have a copy of the source, clone the git repo,

git clone https://code.google.com/a/apache-extras.org/p/cassandra-jdbc/

Build the project,

mvn install -DskipTests

cassandra-jdbc uses Maven. This generate artifacts and installs them into the local Maven repository. I set the skipTests property to tell Maven not to execute any tests. There are some failures in my local repo I have yet to investigate.

2. Determine runtime dependencies

We need to determine the runtime dependencies for the driver so that we know what libraries need to be installed in the next step. The Maven dependency plugin makes this easy. Run the following,

mvn dependency:copy-dependencies -DincludeScope="runtime"

This generates a list of the runtime dependencies under <CASSANDRA_JDBC_HOME>/target/dependency. You should find the following:
  • cassandra-clientutil-1.2.0-beta1.jar
  • cassandra-thrift-1.2.0-beta1.jar
  • commons-lang-2.4.jar
  • guava-12.0.jar
  • jsr305-1.3.9.jar
  • libthrift-0.7.0.jar
  • slf4j-api-1.6.1.jar

3. Create the JBoss module

There are several ways to install to the driver in JBoss AS 7. I am going to describe creating a module since that is what I have done. As it turns out JBoss AS 7 already comes with modules for some of the dependencies; so, we will not include all dependencies in the above list in the module we create. First we need to create the module directory tree.

mkdir -p <JBOSS_HOME>/modules/org/apache-extras/cassandra-jdbc/main

Then copy the cassandra-jdbc build artifact.

cp <CASSANDRA_JDBC_HOME>/target/cassandra-jdbc-1.2.0-SNAPSHOT.jar <JBOSS_HOME>/modules/org/apache-extras/cassandra-jdbc/main 

Now copy the following dependencies to the module directory, right along side the driver JAR file.
  • cassandra-clientutil-1.2.0-beta1.jar
  • cassandra-thrift-1.2.0-beta1.jar
  • guava-12.0.jar
  • jsr305-1.3.9.jar
Do not copy slf4j-api or commons-lang because they are already installed as modules. There is also a module for guava as well, but it is an earlier version; consequently, we include guava in our module so that we have the correct version. Now create a module.xml to define the module resources and dependencies. This file goes in the same directory as the JAR file dependencies and it should look like,



That's it for creating the module. All that is left to do is define the data source and driver.

4. Declare and configure driver and data source

Open <JBOSS_HOME>/standalone/configuration/standalone.xml and scroll down until you reach the data sources subsystem which starts with the tag <subsystem xmlns="urn:jboss:domain:datasources:1.0"> We need to declare a data source as well as a driver. Here is what my additions look like,

This is a minimal configuration for illustration purposes. Changes were recently pushed to the cassandra-jdbc repo to provide more support for connection pooling. For the data source class we could also use org.apache.cassandra.cql.jdbc.PooledCassandraDataSource. Notice in the connection URL that the is a version parameter to tell the server we are using CQL v3. Take a look at the user guide for a full listing of available configuration options for data sources and drivers.

5. Start JBoss AS and verify data source configuration

In a terminal go to <JBOSS_HOME>/bin and then run ./standalone.sh. Now log into the web console at http://localhost:9990. Click on the Profile link in the upper right corner. Then click on Datasources in the menu on the left and you should see something like this,



Finally select the Connection tab and click the Test Connection button as shown below.



We are all set now to use the data source in application code. We can use resource injection just as we would with any other data source.

2 comments:

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  2. This is an excellent article, but unfortunately is 3 years old. I am currently working with Cassandra 2.0.8, and I can't find either of the driver classes mentioned (CassandraDataSource or PooledCassandraDataSource). Have they been replaced by other (newer) classes?

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