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Date: Fri, 11 Jan 2013 21:12:13 +0000 (UTC)
From: "Gregory Chanan (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
Message-ID: <JIRA.12607511.1347567589837.122588.1357938733055@arcas>
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Subject: [jira] [Updated] (HBASE-6775) Use ZK.multi when available for
 HBASE-6710 0.92/0.94 compatibility fix
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     [ https://issues.apache.org/jira/browse/HBASE-6775?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Gregory Chanan updated HBASE-6775:
----------------------------------

     Description: 
This issue introduces the ability for the HMaster to make use of ZooKeeper's multi-update functionality.  This allows certain ZooKeeper operations to complete more quickly and prevents some issues with rare ZooKeeper failure scenarios (see the release note of HBASE-6710 for an example).  This feature is off by default; to enable set "hbase.zookeeper.useMulti" to true in the configuration of the HMaster.

IMPORTANT: "hbase.zookeeper.useMulti" should only be set to true if all ZooKeeper servers in the cluster are on version 3.4+ and will not be downgraded.  ZooKeeper versions before 3.4 do not support multi-update and will not fail gracefully if multi-update is invoked (see ZOOKEEPER-1495).

  was:
HBASE-6710 fixed a 0.92/0.94 compatibility issue by writing two znodes in different formats.

If a ZK failure occurs between the writing of the two znodes, strange behavior can result.

This issue is a reminder to change these two ZK writes to use ZK.multi when we require ZK 3.4+. 

    Release Note: 
hbase.zookeeper.useMulti
Instructs HBase to make use of ZooKeeper's multi-update functionality.
+    This allows certain ZooKeeper operations to complete more quickly and prevents some issues
+    with rare ZooKeeper failure scenarios (see the release note of HBASE-6710 for an example).
+    IMPORTANT: only set this to true if all ZooKeeper servers in the cluster are on version 3.4+
+    and will not be downgraded.  ZooKeeper versions before 3.4 do not support multi-update and will
+    not fail gracefully if multi-update is invoked (see ZOOKEEPER-1495).
    
> Use ZK.multi when available for HBASE-6710 0.92/0.94 compatibility fix
> ----------------------------------------------------------------------
>
>                 Key: HBASE-6775
>                 URL: https://issues.apache.org/jira/browse/HBASE-6775
>             Project: HBase
>          Issue Type: Improvement
>          Components: Zookeeper
>    Affects Versions: 0.94.2
>            Reporter: Gregory Chanan
>            Assignee: Gregory Chanan
>            Priority: Minor
>             Fix For: 0.94.4
>
>         Attachments: HBASE-6775-v2.patch
>
>
> This issue introduces the ability for the HMaster to make use of ZooKeeper's multi-update functionality.  This allows certain ZooKeeper operations to complete more quickly and prevents some issues with rare ZooKeeper failure scenarios (see the release note of HBASE-6710 for an example).  This feature is off by default; to enable set "hbase.zookeeper.useMulti" to true in the configuration of the HMaster.
> IMPORTANT: "hbase.zookeeper.useMulti" should only be set to true if all ZooKeeper servers in the cluster are on version 3.4+ and will not be downgraded.  ZooKeeper versions before 3.4 do not support multi-update and will not fail gracefully if multi-update is invoked (see ZOOKEEPER-1495).

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