Wednesday, January 28, 2009

Adding container level locking to your H.A. Servicemix 4 deployment.

As an improvement to the High Availability features being implemented in the latest versions of the Servicemix 4 Kernel the concept of container level locking has been introduced.

The Container Level locking mechanism allows bundles to be loaded into slave kernel instances in order to provide faster failover performance (when a slave instance becomes the master it will have fewer bundles to load before starting operation). The Container Level refers to the starting priority assigned to each bundle in the OSGI container. These start levels are specified in $SERVICEMIX_HOME/etc/, in the format The core system bundles have levels below 50, where as user bundles have levels greater than 50.

Level: 1 Behavior: A 'cold' standby instance. Core bundles are not loaded into container. Slaves will wait until lock acquired to start server.

Level: <50 Behavior: A 'hot' standby instance. Core bundles are loaded into the container. Slaves will wait until lock acquired to start user level bundles. The console will be accessible for each slave instance at this level.

Level: >50 Behavior: This setting is Not recommended as user bundles will be started.

Container Level locking is supported in both currently supported failover deployment schemes;
  • Simple Lock File
  • JDBC Locking
To make use of this capability the following must be set on each system in the master/slave setup:
  • $SERVICEMIX_HOME/etc/ file updated to include the below entries in addition to other configuration entries to enable H.A.

For more information on how to use the High Availability features supported with Servicemix 4 please visit the users guide.

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