ZooKeeper watchdog monitors the health of the Apache ZooKeeper ensemble, and when quorum is lost, it restarts the ZooKeeper process with a reduced ensemble of the surviving nodes, thereby restoring the quorum. ZooKeeper watchdog is installed as part of the installation process.
The Installation Manager deploys ZooKeeper watchdog during the installation of ZooKeeper. The watchdog is deployed on the servers where ZooKeeper is installed. When the watchdog is deployed, the <install_Dir>/zookeeper/watchdog directory is created in the ZooKeeper installation directory. When you run the startGM.sh script in the <install_Dir>/MailboxUtilities/bin directory, the watchdog is started after the Cassandra, Reaper, and ZooKeeper nodes are started. No additional action is required.
If you need to start or stop the watchdog process, you must run the startGMCoordinateWatchdog.sh and stopGMCoordinateWatchdog.sh scripts in the <install_Dir>/MailboxUtilities/bin directory.
The Installation Manager modifies the watchdog.properties file to set the fully qualified path to the ZooKeeper startup and shutdown scripts. The other watchdog properties must stay as the defaults. The watchdog.properties file is in the <install_Dir>/zookeeper/watchdog/conf directory. To edit the properties, you must open the properties file in a text editor and make the necessary changes.