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From "Thai Bui (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HIVE-17502) Reuse of default session should not throw an exception in LLAP w/ Tez
Date Mon, 11 Sep 2017 14:23:00 GMT
Thai Bui created HIVE-17502:
-------------------------------

             Summary: 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: 2.2.0, 2.1.1
         Environment: HDP 2.6.1.0-129, Hue 4
            Reporter: Thai Bui
            Assignee: Thai Bui


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-2.1.0.2.6.1.0-129.jar:2.1.0.2.6.1.0-129]
	at org.apache.hadoop.hive.ql.exec.tez.TezSessionPoolManager.getSession(TezSessionPoolManager.java:544)
~[hive-exec-2.1.0.2.6.1.0-129.jar:2.1.0.2.6.1.0-129]
	at org.apache.hadoop.hive.ql.exec.tez.TezTask.execute(TezTask.java:147) [hive-exec-2.1.0.2.6.1.0-129.jar:2.1.0.2.6.1.0-129]
	at org.apache.hadoop.hive.ql.exec.Task.executeTask(Task.java:197) [hive-exec-2.1.0.2.6.1.0-129.jar:2.1.0.2.6.1.0-129]
	at org.apache.hadoop.hive.ql.exec.TaskRunner.runSequential(TaskRunner.java:100) [hive-exec-2.1.0.2.6.1.0-129.jar:2.1.0.2.6.1.0-129]
	at org.apache.hadoop.hive.ql.exec.TaskRunner.run(TaskRunner.java:79) [hive-exec-2.1.0.2.6.1.0-129.jar:2.1.0.2.6.1.0-129]
{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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