org.apache.avalon.excalibur.datasource.cluster

Class DefaultRoundRobinDataSourceCluster

java.lang.Object

org.apache.avalon.framework.logger.AbstractLogEnabled

org.apache.avalon.excalibur.datasource.cluster.AbstractDataSourceCluster

org.apache.avalon.excalibur.datasource.cluster.DefaultRoundRobinDataSourceCluster

All Implemented Interfaces:

RoundRobinDataSourceCluster, DataSourceComponent, org.apache.avalon.framework.activity.Disposable, org.apache.avalon.framework.activity.Initializable, org.apache.avalon.framework.component.Component, org.apache.avalon.framework.configuration.Configurable, org.apache.avalon.framework.logger.LogEnabled, org.apache.avalon.framework.service.Serviceable, org.apache.avalon.framework.thread.ThreadSafe

public class DefaultRoundRobinDataSourceCluster
extends AbstractDataSourceCluster
implements RoundRobinDataSourceCluster

The DefaultRoundRobinDataSourceCluster allows the user to specify a cluster of DataSources which all act as one. The Cluster works by cycling through its member DataSources returning a connection from a different one with each call to getConnection().

This form of Clustering has the benefit that it can be used by components without requiring any changes. But care must be taken as to the kind of data written or read from the database. Wich this clustering method, there is no control over which DataSource will provide a connection for any given call.

Round Robin Clusters are useful in cases where lots of read-only data needs to be accessed and multiple copies of the data can be stored on different database servers to balance load.

The Configuration for a 2 database cluster is like this:

   <datasources>
     <roundrobin-cluster name="mydb-cluster" size="2">
       <dbpool index="0">mydb-0</dbpool>
       <dbpool index="1">mydb-1</dbpool>
     </roundrobin-cluster>
   </datasources>
   <cluster-datasources>
     <jdbc name="mydb-0">
       <pool-controller min="1" max="10"/>
       <auto-commit>true</auto-commit>
       <driver>com.database.jdbc.JdbcDriver</driver>
       <dburl>jdbc:driver://host0/mydb</dburl>
       <user>username</user>
       <password>password</password>
     </jdbc>
     <jdbc name="mydb-1">
       <pool-controller min="1" max="10"/>
       <auto-commit>true</auto-commit>
       <driver>com.database.jdbc.JdbcDriver</driver>
       <dburl>jdbc:driver://host1/mydb</dburl>
       <user>username</user>
       <password>password</password>
     </jdbc>
   </cluster-datasources>
 

With the following roles declaration:

   <role name="org.apache.avalon.excalibur.datasource.DataSourceComponentSelector"
       shorthand="datasources"
       default-class="org.apache.avalon.excalibur.component.ExcaliburComponentSelector">
     <hint shorthand="jdbc" class="org.apache.avalon.excalibur.datasource.JdbcDataSource"/>
     <hint shorthand="j2ee" class="org.apache.avalon.excalibur.datasource.J2eeDataSource"/>
     <hint shorthand="roundrobin-cluster"
         class="org.apache.avalon.excalibur.datasource.cluster.DefaultRoundRobinDataSourceCluster"/>
   </role>
   <role name="org.apache.avalon.excalibur.datasource.DataSourceComponentClusterSelector"
       shorthand="cluster-datasources"
       default-class="org.apache.avalon.excalibur.component.ExcaliburComponentSelector">
     <hint shorthand="jdbc" class="org.apache.avalon.excalibur.datasource.JdbcDataSource"/>
     <hint shorthand="j2ee" class="org.apache.avalon.excalibur.datasource.J2eeDataSource"/>
   </role>
 

Since:

4.1

Version:

CVS $Revision: 1.4 $ $Date: 2004/02/28 11:47:20 $

Author:

Avalon Development Team

Field Summary

Fields

Modifier and Type	Field and Description
private int	m_nextIndex
private java.lang.Object	m_semaphore

Fields inherited from class org.apache.avalon.excalibur.datasource.cluster.AbstractDataSourceCluster

m_size

Fields inherited from interface org.apache.avalon.excalibur.datasource.cluster.RoundRobinDataSourceCluster

ROLE

Constructor Summary

Constructors

Constructor and Description
DefaultRoundRobinDataSourceCluster()

Method Summary

Methods

Modifier and Type	Method and Description
java.sql.Connection	getConnection() Returns a Connection to one of the Cluster's member DataSources.

Methods inherited from class org.apache.avalon.excalibur.datasource.cluster.AbstractDataSourceCluster

configure, dispose, getClusterSize, getConnectionForIndex, initialize, service

Methods inherited from class org.apache.avalon.framework.logger.AbstractLogEnabled

enableLogging, getLogger, setupLogger, setupLogger, setupLogger

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.apache.avalon.framework.configuration.Configurable

configure

Field Detail

m_semaphore

private java.lang.Object m_semaphore

m_nextIndex

private int m_nextIndex

Constructor Detail

DefaultRoundRobinDataSourceCluster

public DefaultRoundRobinDataSourceCluster()

Method Detail

getConnection

public java.sql.Connection getConnection()
                                  throws java.sql.SQLException

Returns a Connection to one of the Cluster's member DataSources.

Specified by:

getConnection in interface DataSourceComponent

Returns:

Connection a valid connection for you to use

Throws:

NoValidConnectionException - when there is no valid Connection wrapper available in the classloader.

NoValidConnectionException - when there are no more available Connections in the pool.

NoAvailableConnectionException - when there are no more available Connections in the pool.

java.sql.SQLException