Dan Hecht has posted comments on this change. ( 
http://gerrit.cloudera.org:8080/9718 )

Change subject: IMPALA-6338: Fix flaky test_profile_fragment_instances
......................................................................


Patch Set 1:

(4 comments)

http://gerrit.cloudera.org:8080/#/c/9718/1//COMMIT_MSG
Commit Message:

http://gerrit.cloudera.org:8080/#/c/9718/1//COMMIT_MSG@7
PS1, Line 7: Fix flaky test_profile_fragment_instances
This subject makes it sound like you're fixing the flaky test. But you're 
actually making an impala change, so could you reword this to summarize the 
change?

Otherwise, when looking at git commits, it's hard to know that this change is 
making a subtle coordinator behavior change.


http://gerrit.cloudera.org:8080/#/c/9718/1//COMMIT_MSG@43
PS1, Line 43: Returning results for queries that are cancelled by the user is
            : unaffected as the manual cancel path causes 
WaitForBackendCompletion().
I don't follow that. What does this have to do with query results?  Also, what 
do you mean by the "path causes WaitForBackendCompletion()". Which callpath are 
you referring to?


http://gerrit.cloudera.org:8080/#/c/9718/1/be/src/runtime/coordinator-backend-state.h
File be/src/runtime/coordinator-backend-state.h:

http://gerrit.cloudera.org:8080/#/c/9718/1/be/src/runtime/coordinator-backend-state.h@119
PS1, Line 119:   boost::mutex* lock() { return &lock_; }
> I don't think it will help with the iteration part, but it'll prevent mista
I think we should try hard to not expose the lock out of a class. That's a big 
problem with ClientRequestState.  The fact that it's exposed usually means some 
abstraction is missing or wrong.

(If we really do end up needing to take the series of locks, then it'd be good 
to follow the pattern here: 
https://github.com/apache/impala/blob/dc2f69e5a0b36ca721eeadeec661a251c957410b/be/src/runtime/bufferpool/buffer-allocator.cc#L341)


http://gerrit.cloudera.org:8080/#/c/9718/1/be/src/runtime/coordinator.cc
File be/src/runtime/coordinator.cc:

http://gerrit.cloudera.org:8080/#/c/9718/1/be/src/runtime/coordinator.cc@1028
PS1, Line 1028:   // ensure the profile isn't being updated when we call 
Add(Split|Exec)Stats below.
What are the backend locks protecting in Add*Stats()?  Which profile is the 
comment referring to?



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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: I2f8295e4ec580b476f7668c77aec1348fb2e868c
Gerrit-Change-Number: 9718
Gerrit-PatchSet: 1
Gerrit-Owner: Thomas Tauber-Marshall <[email protected]>
Gerrit-Reviewer: Dan Hecht <[email protected]>
Gerrit-Reviewer: Lars Volker <[email protected]>
Gerrit-Reviewer: Thomas Tauber-Marshall <[email protected]>
Gerrit-Comment-Date: Mon, 26 Mar 2018 23:36:03 +0000
Gerrit-HasComments: Yes

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