Philip Zeyliger has posted comments on this change. ( 
http://gerrit.cloudera.org:8080/8100 )

Change subject: IMPALA-5940. Avoid log spew by using Status::Expected.
......................................................................


Patch Set 1:

(1 comment)

Thanks for the review!

I added in the two messages that Mostafa mentioned on the JIRA. Doing so 
introduced two complexities:

* Whereas I believe we could never log the messages in the first draft, the new 
messages being silenced here (especially RPC timeout) should be logged.
* Now that there's no stack trace, the fact that the messages come as being 
from "status.cc" is not useful.

I see the following ways forward:

* Use draft 1 to silence the easy messages; ignore this new draft 2.
* Use draft 2. Notably, it uses the __FILE__ preprocessor macro. __func__ is 
also a possibility.
* Change the usage pattern. For example STATUS_AND_LOG(...) could be a macro 
that does VLOG and the Status generation. I was very hesitant to add macros for 
this so didn't go that route.
* Something else?

I want to highlight a few more things about patch 2:
* I started off with a signature like Status(..., bool silent, bool 
omit_backtrace), but there were only 3 possible good states. I had bugs in my 
implementation, so decided on an enum instead. It's all private, so there's 
little API risk here.
* There's a copy of ErrorMsg going on when Status::NoTrace() takes an error 
code and a string. We do several of them in various Status signatures. Given 
that we used to also compute an entire back trace, I think this is ok.
* I didn't add a new test. I didn't find any tests that look like they're 
testing our logging behavior. Happy for suggestions, though I think it's 
overkill.
* I don't know how to reproduce RPC timeouts. I "kill -STOP"ed an impalad, but 
that wasn't enough. Curious for pointers.

http://gerrit.cloudera.org:8080/#/c/8100/1//COMMIT_MSG
Commit Message:

http://gerrit.cloudera.org:8080/#/c/8100/1//COMMIT_MSG@7
PS1, Line 7: IMPALA-5940. Avoid log spew by using Status::Expected.
> IMPALA-5940: (colon not dot)
Done



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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: I38088482377a1c3e794a9c8178ef83f29957a330
Gerrit-Change-Number: 8100
Gerrit-PatchSet: 1
Gerrit-Owner: Philip Zeyliger <[email protected]>
Gerrit-Reviewer: Alex Behm <[email protected]>
Gerrit-Reviewer: Mostafa Mokhtar <[email protected]>
Gerrit-Reviewer: Philip Zeyliger <[email protected]>
Gerrit-Comment-Date: Tue, 26 Sep 2017 23:03:30 +0000
Gerrit-HasComments: Yes

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