Sailesh Mukil has posted comments on this change.

Change subject: IMPALA-5558: Reopen stale client connection
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Patch Set 7:

(5 comments)

http://gerrit.cloudera.org:8080/#/c/7284/7//COMMIT_MSG
Commit Message:

PS7, Line 13: It may still be buffered in the kernel
            : if there is room for it.
If you have a link that explains how this could happen, it would be a good idea 
to reference it here.


PS7, Line 15: If an Impalad node is restarted, a stale client connection may
            : still allow send() to succeed
Reword for clarity:

If an Impalad node is restarted, a stale client connection to that node may 
still allow send() to appear succeed even though the payload wasn't sent.


http://gerrit.cloudera.org:8080/#/c/7284/7/be/src/runtime/client-cache.h
File be/src/runtime/client-cache.h:

Line 203:       client_is_unrecoverable_(false) {
Not for this patch, but this would be a good place to inject a fault, i.e. not 
return a client. That would have caught IMPALA-5576.
Feel free to leave a TODO if you agree.


http://gerrit.cloudera.org:8080/#/c/7284/7/be/src/runtime/coordinator-backend-state.cc
File be/src/runtime/coordinator-backend-state.cc:

PS7, Line 356: connect_success
What is 'connect_success' trying to achieve? It looks like it wants to keep 
track of whether we were able to ever get a connection at some point in the 
retry loop (except the last iteration).

So if we were able to get a connection (which could have been stale) but were 
not able to successfully send the Cancel RPC, we still would send true here.


http://gerrit.cloudera.org:8080/#/c/7284/7/be/src/runtime/query-state.cc
File be/src/runtime/query-state.cc:

PS7, Line 237: !client_status.ok()
> I think that adding this here is essentially equivalent to the bug IMPALA-5
No, this is still outside the loop, so we're still at least trying 3 times 
before calling it quits. Adding this check inside the loop would be equivalent 
to IMPALA-5576.


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Gerrit-MessageType: comment
Gerrit-Change-Id: I4d722c8ad3bf0e78e89887b6cb286c69ca61b8f5
Gerrit-PatchSet: 7
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Michael Ho <[email protected]>
Gerrit-Reviewer: Dan Hecht <[email protected]>
Gerrit-Reviewer: Juan Yu <[email protected]>
Gerrit-Reviewer: Lars Volker <[email protected]>
Gerrit-Reviewer: Matthew Jacobs <[email protected]>
Gerrit-Reviewer: Michael Ho <[email protected]>
Gerrit-Reviewer: Mostafa Mokhtar <[email protected]>
Gerrit-Reviewer: Sailesh Mukil <[email protected]>
Gerrit-HasComments: Yes

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