[jira] Resolved: (HBASE-1800) Too many ZK connections

["Jean-Daniel Cryans (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HBASE-1800?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jean-Daniel Cryans resolved HBASE-1800.
---------------------------------------

      Resolution: Fixed
        Assignee: Jean-Daniel Cryans
    Hadoop Flags: [Reviewed]

Committed to branch and trunk, this should help fixing a lot of problems new users were getting and provide faster HTable instantiations. 

> Too many ZK connections
> -----------------------
>
>                 Key: HBASE-1800
>                 URL: https://issues.apache.org/jira/browse/HBASE-1800
>             Project: Hadoop HBase
>          Issue Type: Improvement
>            Reporter: Jean-Daniel Cryans
>            Assignee: Jean-Daniel Cryans
>             Fix For: 0.20.0, 0.21.0
>
>         Attachments: HBASE-1800-v1.patch, HBASE-1800-v2.patch, HBASE-1800-v3.patch
>
>
> Currently we open tons of new connections to Zookeeper, like every time we instantiate a new HTable. There is a maximum number of client connections as described here:
> {code}
>   <property>
>     <name>hbase.zookeeper.property.maxClientCnxns</name>
>     <value>30</value>
>     <description>Property from ZooKeeper's config zoo.cfg.
>     Limit on number of concurrent connections (at the socket level) that a
>     single client, identified by IP address, may make to a single member of
>     the ZooKeeper ensemble. Set high to avoid zk connection issues running
>     standalone and pseudo-distributed.
>     </description>
>   </property>
> {code}
> If you hit that max number, ZK will just refuse your connections. Suppose you have 4 maps running on a server hosting a RS, you may actually lose your connection in the RS and eventually hit a session timeout. Maybe we should singleton ZKW?

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