[jira] [Created] (HBASE-26459) HMaster should move non-meta region only if meta is ONLINE

["Viraj Jasani (Jira)" <ji...@apache.org>]

Viraj Jasani created HBASE-26459:
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             Summary: HMaster should move non-meta region only if meta is ONLINE
                 Key: HBASE-26459
                 URL: https://issues.apache.org/jira/browse/HBASE-26459
             Project: HBase
          Issue Type: Improvement
    Affects Versions: 1.7.1
            Reporter: Viraj Jasani
             Fix For: 1.7.2


Any non-meta region movement has dependency over meta's availability, hence it is important for any non-meta region to wait for meta to be assigned and be available for scan before attempting to move non-meta region.

This concept has already been well managed by SCP (ServerCrashProcedure) on HBase 1.x and 2.x versions. However, for 1.x versions, HMaster#move API doesn't check for any prerequisite of meta being available before attempting to move any non-meta region.

On the other hand, 2.x versions already have TransitRegionStateProcedure (TRSP) in place that uses lock _LockState.LOCK_EVENT_WAIT_ in case if meta is not yet assigned and loaded in AssignmentManager's memory:
{code:java}
@Override
protected boolean waitInitialized(MasterProcedureEnv env) {
  if (TableName.isMetaTableName(getTableName())) {
    return false;
  }
  // First we need meta to be loaded, and second, if meta is not online then we will likely to
  // fail when updating meta so we wait until it is assigned.
  AssignmentManager am = env.getAssignmentManager();
  return am.waitMetaLoaded(this) || am.waitMetaAssigned(this, getRegion());
}
 {code}
For 1.x versions, it is recommended to introduce configurable wait time in master's region move API for non-meta region movement until meta region is available. If meta remains in transition after the wait time elapses, we should fail fast and avoid non-meta region move.



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