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From "cuijianwei (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-13814) AssignmentManager does not write the correct server name into Zookeeper when unassign region
Date Sat, 30 May 2015 08:47:17 GMT
cuijianwei created HBASE-13814:

             Summary: AssignmentManager does not write the correct server name into Zookeeper
when unassign region
                 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

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:
          versionOfClosingNode = ZKAssign.createNodeClosing(
            master.getZooKeeper(), region, master.getServerName());
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:
    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 &&
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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