How do I configure c3p0 for a grails 2.X application with multiple datasources?

Question

I'm trying to find an easy-to-follow solution (possibly an answer to this question) for configuring c3p0 connection pooling on a grails 2.X web app with multiple datasources. I have not been able to find any clear and easy help via google searching.

The answer I'm looking for will say the following:

1) What jars are needed

2) What grails files need to be modified

3) Examples of what to put in these grails files including import statements and example code.

Assume I have two datasources in my app, dataSource and dataSource_A configured in DataSource.groovy.

How do I configure c3p0 connection pooling for multiple datasources in a grails 2.X web app?

Answer 1

Here is the corresponding documentation. This blog provides a code example how to delay DataSource creation in Grails... and it is possible to use C3P0 in such a code.

As Grails comes with DBCP by default, I do not find relevant to add code to setup C3P0 pooling (and later replace the default transaction manager...) when it is possible to delegate DataSource and pooling configuration to the underlying container, for instance Tomcat or JBoss. So I recommend that way of doing and here is an example how to setup C3P0 for a Tomcat DataSource, just add its jar in lib directory.

Now, when configuring multiple DataSources, you should take care to the section about the lacking two-phase-commit support in Grails.

If you expect operations done on connections from your two DataSource to be included in a single transaction (commit on both if success, rollback on both if failure), you will have to use a XA transaction manager.

In that case, I recommend you to deploy in JBoss and configure DataSources and pooling in JBoss itself, the JDBC driver must be installed in JBoss libraries.

You will get benefits of the included XA transaction manager. On Grails side, the DataSource is configured to query a JNDI resource-ref entry declared in WEB-INF/web.xml and WEB-INF/jboss-web.xml files of your WAR file.

dataSource {
    jndiName = "java:comp/env/myDataSource"
}

Answer 2

datasource.groovy / External configuration file

   dataSource {
    pooled = true
    dbCreate = "create-drop"
    url = "jdbc:mysql://<ip address>/test1"
    driverClassName = "com.mysql.jdbc.Driver"
    username = "test"
    password = "test123" 
   }

   dataSource_A {
      pooled = true
      dbCreate = "create-drop"
      url = "jdbc:mysql://<ip address>/test2"
      driverClassName = "com.mysql.jdbc.Driver"
      username = "test"
      password = "test123" 
  }

resources.groovy

 dataSource(ComboPooledDataSource) { bean ->
    idleConnectionTestPeriod = 1 * 60 * 60
    testConnectionOnCheckin = true
    bean.destroyMethod = 'close'
    user = grailsApplication.config.dataSource.username
    password = grailsApplication.config.dataSource.password
    driverClass = grailsApplication.config.dataSource.driverClassName
    jdbcUrl = grailsApplication.config.dataSource.url
}


dataSource_A(ComboPooledDataSource) { bean ->

    idleConnectionTestPeriod = 1 * 60 * 60
    testConnectionOnCheckin = true
    bean.destroyMethod = 'close'
    user = grailsApplication.config.dataSource_A.username
    password = grailsApplication.config.dataSource_A.password
    driverClass = grailsApplication.config.dataSource_A.driverClassName
    jdbcUrl = grailsApplication.config.dataSource_A.url

}

c3p0.jar in the project's lib folder.

These are the only changes that are required.