18.3. Container-level Locking

Overview

Container-level locking allows bundles to be preloaded into the slave kernel instance in order to provide faster failover performance. Container-level locking is supported in both the simple file and JDBC locking mechanisms.

Configuring container-level locking

To implement container-level locking, add the following to the etc/system.properties file on each system in the master/slave setup:

Example 18.7. Container-level Locking Configuration

karaf.lock=true
karaf.lock.level=50
karaf.lock.delay=10000
The karaf.lock.level property tells the Red Hat JBoss Fuse instance how far up the boot process to bring the OSGi container. Bundles assigned the same start level or lower will then also be started in that JBoss Fuse instance.
Bundle start levels are specified in etc/startup.properties, in the format BundleName.jar=level. The core system bundles have levels below 50, where as user bundles have levels greater than 50.

Table 18.1. Bundle Start Levels

Start Level Behavior
1A 'cold' standby instance. Core bundles are not loaded into container. Slaves will wait until lock acquired to start server.
<50A '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.
>50This setting is not recommended as user bundles will be started.

Avoiding port conflicts

When using a 'hot' spare on the same host you need to set the JMX remote port to a unique value to avoid bind conflicts. You can edit the fuse start script (or the karaf script on a child instance) to include the following:
DEFAULT_JAVA_OPTS="-server $DEFAULT_JAVA_OPTS -Dcom.sun.management.jmxremote.port=1100 -Dcom.sun.management.jmxremote.authenticate=false"