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From GitBox <...@apache.org>
Subject [GitHub] [zookeeper] enixon commented on a change in pull request #1045: ZOOKEEPER-3400: Add documentation on local sessions
Date Wed, 04 Sep 2019 18:48:56 GMT
enixon commented on a change in pull request #1045: ZOOKEEPER-3400: Add documentation on local
sessions
URL: https://github.com/apache/zookeeper/pull/1045#discussion_r320918230
 
 

 ##########
 File path: zookeeper-docs/src/main/resources/markdown/zookeeperProgrammers.md
 ##########
 @@ -503,6 +503,85 @@ new list and failing to connect, the client moves back to the normal
mode of ope
 an arbitrary server from the connectString and attempts to connect to it. If that fails,
it will continue
 trying different random servers in round robin. (see above the algorithm used to initially
choose a server)
 
+**local session**.Added in 3.5.0, mainly implemented by [ZOOKEEPER-1147](https://issues.apache.org/jira/browse/ZOOKEEPER-1147).
+
+- Background:The create and close of session is costly in zookeeper, especially when these
operations of sessions need a
+quorum confirmation by leader, which we call this session type: global session. it will be
a bottle neck for ZooKeeper ensemble
+when it wants to handle thousands of client connections.
+So after 3.5.0, we introduce a new type of session: local session which doesn't have a full
functionality of a normal(global) session.
+,this feature will be available by turning on *localSessionsEnabled*.
+
+when *localSessionsUpgradingEnabled* is disable:
+
+- Local sessions cannot create ephemeral nodes
+
+- Once a local session is lost, users cannot re-establish it using the session-id/password.
The session and its watches are gone for good.
 
 Review comment:
   Note that losing the tcp connection does not necessarily imply that the session is lost.
If the connection can be reestablished with the same zk server before the session timeout
then the client can continue (it simply cannot move to another server).

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