The Talend ESB instances share a lock on the filesystem. It means that the filesystem storing the lock has to be accessible to the different instances (using SAN, NFS, and so on).
The configuration of the lock system has to be defined in the etc/system.properties file, on each instance (master/slave):
karaf.lock=true karaf.lock.class=org.apache.karaf.main.lock.SimpleFileLock karaf.lock.dir=<PathToLockFileDirectory> karaf.lock.delay=10000
karaf.lockproperty enables the HA/failover mechanism.
karaf.lock.classproperty contains the class name providing the lock implementation. Here, the filesystem lock is used.
karaf.lock.dirproperty contains the location where the lock will be written. All instances have to share the same lock.
karaf.lock.delayproperty is the interval period (in milliseconds) to check if the lock has been released or not.