https://community.cloudera.com/t5/Support-Questions/ZKFC-maintains-session-for-namenode-in-zookeeper/m-p/390150#M247214 <P>How does the ZKFC running in the namenode server maintain a open session in zookeeper?</P> Thu, 11 Jul 2024 12:13:29 GMT NaveenBlaze 2024-07-11T12:13:29Z https://community.cloudera.com/t5/Support-Questions/ZKFC-maintains-session-for-namenode-in-zookeeper/m-p/390150#M247214 <P>How does the ZKFC running in the namenode server maintain a open session in zookeeper?</P> Thu, 11 Jul 2024 12:13:29 GMT https://community.cloudera.com/t5/Support-Questions/ZKFC-maintains-session-for-namenode-in-zookeeper/m-p/390150#M247214 NaveenBlaze 2024-07-11T12:13:29Z https://community.cloudera.com/t5/Support-Questions/ZKFC-maintains-session-for-namenode-in-zookeeper/m-p/390509#M247281 <P><SPAN>When the local NameNode is healthy, the ZKFC holds a session open in ZooKeeper. If the local NameNode is active, it also holds a special “lock” znode. This lock uses ZooKeeper’s support for “ephemeral” nodes; if the session expires, the lock node will be automatically deleted.</SPAN></P><P><SPAN>Ephemeral znodes -&nbsp;</SPAN><SPAN>These znodes exists as long as the session that created the znode is active. When the session ends the znode is deleted. Zookeeper has a concept of Watches which can be set on znodes to track them for any changes.</SPAN></P><P><SPAN>Check the link how Watches work in zookeeper -</SPAN></P><P><SPAN><A href="https://zookeeper.apache.org/doc/current/zookeeperProgrammers.html#ch_zkWatches" target="_blank">https://zookeeper.apache.org/doc/current/zookeeperProgrammers.html#ch_zkWatches</A></SPAN></P> Wed, 17 Jul 2024 16:08:26 GMT https://community.cloudera.com/t5/Support-Questions/ZKFC-maintains-session-for-namenode-in-zookeeper/m-p/390509#M247281 shubham_sharma 2024-07-17T16:08:26Z