Thai Bui commented on HIVE-17502:

Hi [~vgarg], I would definitely want to get this patch onto 3.0.0 if possible. 
At Bazaarvoice, we are currently maintain a separate branch to apply this patch 
and pushing this upstream would remove that effort, we are also currently 
testing using 3.0 in production since early this year (with Hadoop 3.0 but soon 
to upgrade to 3.1). If you guys need help testing the branch, we are that the 
perfect stage for that.

Please let me know what I need to do to get this approved & merged to 3.0.0. 

cc: [~thejas]

> Reuse of default session should not throw an exception in LLAP w/ Tez
> ---------------------------------------------------------------------
>                 Key: HIVE-17502
>                 URL: https://issues.apache.org/jira/browse/HIVE-17502
>             Project: Hive
>          Issue Type: Bug
>          Components: llap, Tez
>    Affects Versions: 2.1.1, 2.2.0
>         Environment: HDP, Hue 4
>            Reporter: Thai Bui
>            Assignee: Thai Bui
>            Priority: Major
>             Fix For: 3.1.0
>         Attachments: HIVE-17502.patch
> Hive2 w/ LLAP on Tez doesn't allow a currently used, default session to be 
> skipped mostly because of this line 
> https://github.com/apache/hive/blob/master/ql/src/java/org/apache/hadoop/hive/ql/exec/tez/TezSessionPoolManager.java#L365.
> However, some clients such as Hue 4, allow multiple sessions to be used per 
> user. Under this configuration, a Thrift client will send a request to either 
> reuse or open a new session. The reuse request could include the session id 
> of a currently used snippet being executed in Hue, this causes HS2 to throw 
> an exception:
> {noformat}
> 2017-09-10T17:51:36,548 INFO  [Thread-89]: tez.TezSessionPoolManager 
> (TezSessionPoolManager.java:canWorkWithSameSession(512)) - The current user: 
> hive, session user: hive
> 2017-09-10T17:51:36,549 ERROR [Thread-89]: exec.Task 
> (TezTask.java:execute(232)) - Failed to execute tez graph.
> org.apache.hadoop.hive.ql.metadata.HiveException: The pool session 
> sessionId=5b61a578-6336-41c5-860d-9838166f97fe, queueName=llap, user=hive, 
> doAs=false, isOpen=true, isDefault=true, expires in 591015330ms should have 
> been returned to the pool
>       at 
> org.apache.hadoop.hive.ql.exec.tez.TezSessionPoolManager.canWorkWithSameSession(TezSessionPoolManager.java:534)
>  ~[hive-exec-]
>       at 
> org.apache.hadoop.hive.ql.exec.tez.TezSessionPoolManager.getSession(TezSessionPoolManager.java:544)
>  ~[hive-exec-]
>       at org.apache.hadoop.hive.ql.exec.tez.TezTask.execute(TezTask.java:147) 
> [hive-exec-]
>       at org.apache.hadoop.hive.ql.exec.Task.executeTask(Task.java:197) 
> [hive-exec-]
>       at 
> org.apache.hadoop.hive.ql.exec.TaskRunner.runSequential(TaskRunner.java:100) 
> [hive-exec-]
>       at org.apache.hadoop.hive.ql.exec.TaskRunner.run(TaskRunner.java:79) 
> [hive-exec-]
> {noformat}
> Note that every query is issued as a single 'hive' user to share the LLAP 
> daemon pool, a set of pre-determined number of AMs is initialized at setup 
> time. Thus, HS2 should allow new sessions from a Thrift client to be used out 
> of the pool, or an existing session to be skipped and an unused session from 
> the pool to be returned. The logic to throw an exception in the  
> `canWorkWithSameSession` doesn't make sense to me.
> I have a solution to fix this issue in my local branch at 
> https://github.com/thaibui/hive/commit/078a521b9d0906fe6c0323b63e567f6eee2f3a70.
>  When applied, the log will become like so
> {noformat}
> 2017-09-10T09:15:33,578 INFO  [Thread-239]: tez.TezSessionPoolManager 
> (TezSessionPoolManager.java:canWorkWithSameSession(533)) - Skipping default 
> session sessionId=6638b1da-0f8a-405e-85f0-9586f484e6de, queueName=llap, 
> user=hive, doAs=false, isOpen=true, isDefault=true, expires in 591868732ms 
> since it is being used.
> {noformat}
> A test case is provided in my branch to demonstrate how it works. If possible 
> I would like this patch to be applied to version 2.1, 2.2 and master. Since 
> we are using 2.1 LLAP in production with Hue 4, this patch is critical to our 
> success.
> Alternatively, if this patch is too broad in scope, I propose adding an 
> option to allow "skipping of currently used default sessions". With this new 
> option default to "false", existing behavior won't change unless the option 
> is turned on.
> I will prepare an official path if this change to master &/ the other 
> branches is acceptable. I'm not an contributor &/ committer, this will be my 
> first time contributing to Hive and the Apache foundation. Any early review 
> is greatly appreciated, thanks!

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