[jira] [Created] (HBASE-22810) Initialize an separate ThreadPoolExecutor for taking/restoring snapshot

["Zheng Hu (JIRA)" <ji...@apache.org>]

Zheng Hu created HBASE-22810:
--------------------------------

             Summary: Initialize an separate ThreadPoolExecutor for taking/restoring snapshot 
                 Key: HBASE-22810
                 URL: https://issues.apache.org/jira/browse/HBASE-22810
             Project: HBase
          Issue Type: Improvement
            Reporter: Zheng Hu
            Assignee: Zheng Hu


In EventType class, we have the following definition, means  taking snapshot & restoring snapshot are use the MASTER_TABLE_OPERATIONS  Executor now. 

{code}
  /**
   * Messages originating from Client to Master.<br>
   * C_M_SNAPSHOT_TABLE<br>
   * Client asking Master to snapshot an offline table.
   */
  C_M_SNAPSHOT_TABLE        (48, ExecutorType.MASTER_TABLE_OPERATIONS),
  /**
   * Messages originating from Client to Master.<br>
   * C_M_RESTORE_SNAPSHOT<br>
   * Client asking Master to restore a snapshot.
   */
  C_M_RESTORE_SNAPSHOT      (49, ExecutorType.MASTER_TABLE_OPERATIONS),
{code}

But when I checked the MASTER_TABLE_OPERATIONS thread pool initialization, I see : 
{code}
  private void startServiceThreads() throws IOException{
   // ...  some other code initializing .... 

   // We depend on there being only one instance of this executor running
   // at a time.  To do concurrency, would need fencing of enable/disable of
   // tables.
   // Any time changing this maxThreads to > 1, pls see the comment at
   // AccessController#postCompletedCreateTableAction
   this.executorService.startExecutorService(ExecutorType.MASTER_TABLE_OPERATIONS, 1);
   startProcedureExecutor();
{code}
That's to say,  for CPs  enable or disable table sequencely,  we will create a ThreadPoolExecutor with threadPoolSize=1.   Then we actually cann't accomplish the snapshoting  concurrence even if they are total difference tables, says if there are two table snapshoting request, and the Table A cost  5min for snapshoting, then the Table B need to wait 5min and once Table A finish its snapshot , then Table B will start the snapshot.

While we've setting the snapshot timeout, so it will be easy to timeout for table B snapshoting .   Actually,  we can create a separate thead pool for snapshot operations only.






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