[jira] [Commented] (HIVE-13149) Remove some unnecessary HMS connections from HS2

["Aihua Xu (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-13149?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15174452#comment-15174452 ] 

Aihua Xu commented on HIVE-13149:
---------------------------------

Attached the patch-2: to fix the issue observed from the unit tests. We need to pass in a copy of conf to the Hive instance since otherwise it's sharing with the session one. 

> Remove some unnecessary HMS connections from HS2 
> -------------------------------------------------
>
>                 Key: HIVE-13149
>                 URL: https://issues.apache.org/jira/browse/HIVE-13149
>             Project: Hive
>          Issue Type: Sub-task
>          Components: HiveServer2
>    Affects Versions: 2.0.0
>            Reporter: Aihua Xu
>            Assignee: Aihua Xu
>         Attachments: HIVE-13149.1.patch, HIVE-13149.2.patch
>
>
> In SessionState class, currently we will always try to get a HMS connection in {{start(SessionState startSs, boolean isAsync, LogHelper console)}} regardless of if the connection will be used later or not. 
> When SessionState is accessed by the tasks in TaskRunner.java, although most of the tasks other than some like StatsTask, don't need to access HMS. Currently a new HMS connection will be established for each Task thread. If HiveServer2 is configured to run in parallel and the query involves many tasks, then the connections are created but unused.
> {noformat}
>   @Override
>   public void run() {
>     runner = Thread.currentThread();
>     try {
>       OperationLog.setCurrentOperationLog(operationLog);
>       SessionState.start(ss);
>       runSequential();
> {noformat}



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