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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-13814) AssignmentManager does not write the correct server name into Zookeeper when unassign region
Date Tue, 09 Jun 2015 03:59:00 GMT

    [ https://issues.apache.org/jira/browse/HBASE-13814?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14578275#comment-14578275

Lars Hofhansl commented on HBASE-13814:


Maybe it's time to do another maintenance release.

> AssignmentManager does not write the correct server name into Zookeeper when unassign
> --------------------------------------------------------------------------------------------
>                 Key: HBASE-13814
>                 URL: https://issues.apache.org/jira/browse/HBASE-13814
>             Project: HBase
>          Issue Type: Bug
>          Components: Region Assignment
>    Affects Versions: 0.94.27
>            Reporter: cuijianwei
>            Priority: Minor
>         Attachments: HBASE-13814-0.94-v1.patch
> When moving region, the region will firstly be unassigned from corresponding region server
by the method AssignmentManager#unassign(). AssignmentManager will write the region info and
the server name into Zookeeper by the following code:
> {code}
>           versionOfClosingNode = ZKAssign.createNodeClosing(
>             master.getZooKeeper(), region, master.getServerName());
> {code}
> It seems that the AssignmentManager misuses the master's name as the server name. If
the ROOT region is being moved and the region server holding the ROOT region is just crashed.
The Master will try to start a MetaServerShutdownHandler if the server is judged as holding
meta region. The judgment will be done by the method AssignmentManager#isCarryingRegion, and
the method will firstly check the server name in Zookeeper:
> {code}
>     ServerName addressFromZK = (data != null && data.getOrigin() != null) ?
>       data.getOrigin() : null;
>     if (addressFromZK != null) {
>       // if we get something from ZK, we will use the data
>       boolean matchZK = (addressFromZK != null &&
>         addressFromZK.equals(serverName));
> {code}
> The wrong server name from Zookeeper will make the server not be judged as holding the
ROOT region. Then, the master will start a ServerShutdownHandler. Unlike MetaServerShutdownHandler,
the ServerShutdownHandler won't assign ROOT region firstly, making the ROOT region won't be
assigned forever. In our test environment, we encounter this problem when moving ROOT region
and stopping the region server concurrently.

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