Typical use cases , Naming service Configuration management Synchronization Leader election Message Queue Notification system 11. Please note that Found is now known as Elastic Cloud. The latter is used by the proxies to stop indexing when the customer exceeds their disk quota and the first one will at some stage in the future be used to upgrade customers plans when needed. An ephemeral zNode is a node that will disappear when the session of its owner ends. and feeds the relevant zk configurations to zk on start). However if we create the cluster of five nodes, even if two nodes go offline, Apache ZooKeeper will still be functional as we still have majority of nodes in service. But such a setup would require maintaining our bespoke solutions while also operating on Twine, adding more complexity without eliminating any. ZooKeeper Use Cases: There are many use cases of ZooKeeper. A typical use case for ephemeral nodes is when using ZooKeeper for discovery of hosts in your distributed system. {"serverDuration": 69, "requestCorrelationId": "6c43b042cc12fe1b"}, http://wiki.apache.org/hadoop/Hbase/MasterRewrite#tablestate, http://hadoop.apache.org/zookeeper/docs/current/recipes.html#sc_outOfTheBox, http://wiki.apache.org/hadoop/Hbase/MasterRewrite#regionstate, master watches /regionservers for any child changes, as each region server becomes available to do work (or track state if up but not avail) it creates an ephemeral node, master watches /regionserver/ and cleans up if RS goes away or changes status, /tables/ which gets created when master notices new region server, RS host:port watches this node for any child changes, /tables// znode for each region assigned to RS host:port, RS host:port watches this node in case reassigned by master, or region changes state, /tables///- znode created by master, RS deletes old state znodes as it transitions out, oldest entry is the current state, always 1 or more znode here – the current state, 1000 watches, one each by RS on /tables (1 znode) – really this may not be necessary, esp after is created (reduce noise by not setting when not needed), 1000 watches, one each by RS on /tables/ (1000 znodes), 100K watches, 100 for each RS on /tables//