The Talend ESB failover capability uses a lock system.
This container-level lock system allows bundles installed on the master to be preloaded on the slave, in order to provide faster failover performance.
Two types of lock are supported:
When a first instance starts, if the lock is available, it takes the lock and become the master.
If a second instance starts, it tries to acquire the lock. As the lock is already hold by the master, the instance becomes a slave, in standby mode (not active). A slave periodically check if the lock has been released or not.