Tim Armstrong has posted comments on this change.

Change subject: IMPALA-5282: Handle overflows in computeResourceProfile().
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Patch Set 1:

(1 comment)

http://gerrit.cloudera.org:8080/#/c/7084/1/fe/src/main/java/org/apache/impala/service/Frontend.java
File fe/src/main/java/org/apache/impala/service/Frontend.java:

Line 1019:     try {
> I agree that this try/catch is a crutch for missing tests.
We did rely on the estimates for admission control before when query mem limits 
were not set, there was just logic that worked around the estimates being not 
set.

This overflow bug was present before the resource profile change but was 
partially masked. Instead of an error there would have been a warning and 
admission control would use --rm_default_memory.

My concern is that hiding a bug in a warning message will just prevent us from 
finding the bugs until something else  breaks as an indirect consequence. Part 
of my goal with that change was to get it in before the buffer pool stuff and 
make sure that the invariants actually held before we built more things on top 
of it. E.g. without the invariant check there's no way the random query 
generator can find bugs like this.

My preference is to fix this specific bug and leave it at that, unless there's 
a specific gap in test coverage that we need more time to address. If we don't 
have a specific goal for the test coverage we need we'll just be giving the 
code opportunity to bit-rot before it gets turned on again for the buffer pool 
work. If we really needed to do that we could add code that marked the 
estimates as invalid and fell back to --rm_default_memory.


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Gerrit-MessageType: comment
Gerrit-Change-Id: I8a83a76141853d3274f812e5a531f456e1b110b1
Gerrit-PatchSet: 1
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Alex Behm <[email protected]>
Gerrit-Reviewer: Alex Behm <[email protected]>
Gerrit-Reviewer: Tim Armstrong <[email protected]>
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