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From "Sailesh Mukil (Code Review)" <ger...@cloudera.org>
Subject [Impala-ASF-CR] IMPALA-5199: prevent hang on empty row batch exchange
Date Fri, 08 Sep 2017 00:03:31 GMT
Sailesh Mukil has posted comments on this change.

Change subject: IMPALA-5199: prevent hang on empty row batch exchange
......................................................................


Patch Set 2:

The fix looks good to me, and should work fine for most cases.

One case I'm worried about is that, under heavy load, if a receiver deregisters itself early
(due to a LIMIT, etc.), and the sender sends the 'eos' after STREAM_EXPIRATION_TIME_MS, the
query would have previously succeeded, even though the sender couldn't find the receiver in
CloseSender(). And the query would be right to succeed in this case since the 'eos' here is
spurious as the receiver is already gone. Although, I know this counts as succeeding "by mistake".

Now, we would be failing these queries. And given that we see the 'DATASTREAM_SENDER_TIMEOUT'
fairly often, that would regress a few workloads.

What do you think?

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Gerrit-MessageType: comment
Gerrit-Change-Id: Ib370ebe44e3bb34d3f0fb9f05aa6386eb91c8645
Gerrit-PatchSet: 2
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Tim Armstrong <tarmstrong@cloudera.com>
Gerrit-Reviewer: Sailesh Mukil <sailesh@cloudera.com>
Gerrit-HasComments: No

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