[Impala-CR](cdh5-trunk) IMPALA-3633: cancel fragment if coordinator is gone

["Internal Jenkins (Code Review)" <ge...@cloudera.org>]

Internal Jenkins has submitted this change and it was merged.

Change subject: IMPALA-3633: cancel fragment if coordinator is gone
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IMPALA-3633: cancel fragment if coordinator is gone

The bug is that return_val.status is an optional field, so setting
the status without __isset is equivalent to Status::OK(). This
meant that fragment did not get notified when reporting status
if the coordinator had gone away. This means that is a cancel
RPC was lost, we could be left with zombie fragments with no
coordinator that kept on running until completion.

Testing:
I couldn't see a way to replicate this reliably with our existing test
setup, since it requires some RPCs to be dropped to get into this state.
I manually tested by commenting out CancelRemoteFragments(), starting a
long-running query then cancelling it. Before the patch, perf top showed
that the fragments continue to execute the query. After the patch, the
fragments stopped executing quickly.

Change-Id: I62ab6f4df7c0ee60c6aa6291513f9f0cbfac3fe7
Reviewed-on: http://gerrit.cloudera.org:8080/3238
Reviewed-by: Tim Armstrong <ta...@cloudera.com>
Tested-by: Internal Jenkins
---
M be/src/service/impala-server.cc
1 file changed, 4 insertions(+), 7 deletions(-)

Approvals:
  Internal Jenkins: Verified
  Tim Armstrong: Looks good to me, approved



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Gerrit-MessageType: merged
Gerrit-Change-Id: I62ab6f4df7c0ee60c6aa6291513f9f0cbfac3fe7
Gerrit-PatchSet: 4
Gerrit-Project: Impala
Gerrit-Branch: cdh5-trunk
Gerrit-Owner: Tim Armstrong <ta...@cloudera.com>
Gerrit-Reviewer: Dan Hecht <dh...@cloudera.com>
Gerrit-Reviewer: Internal Jenkins
Gerrit-Reviewer: Matthew Jacobs <mj...@cloudera.com>
Gerrit-Reviewer: Sailesh Mukil <sa...@cloudera.com>
Gerrit-Reviewer: Tim Armstrong <ta...@cloudera.com>