Don't buffer stdout/stderr in command_wrapper.py

Don't buffer stdout/stderr in command_wrapper.py

Otherwise, commands that take a long time to complete, but produce some status
output, such as gsutil cp, will cause the buildbot's timeout to trigger.

BUG=none
TEST=manually, works on linux :)

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=134087

[jochen (gone - plz use gerrit), 2012-04-13 10:53:53]

plz review

[cmp, 2012-04-17 09:19:14]

lgtm

I recall implementing something similar using output processors in threads and
found that the threads themselves introduced timing issues that caused
stdout+stderr to be printed erratically between separate calls to the wrapper. 
I assume you know that already, just noting here for posterity.

Since this patch changes the way that output is handled for all platforms (and
could affect how well this works at all in some or all places), when you land it
please keep an eye on the codesearch bot's upload, and chromium.perf's win
release upload and download (upload on Win Builder, download on XP Perf 1, for
example).

[commit-bot: I haz the power, 2012-04-26 10:37:20]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jochen@chromium.org/10085001/2001

[commit-bot: I haz the power, 2012-04-26 10:37:44]

Change committed as 134087

[djmm, 2012-05-03 01:00:03]

This change has had some ripple effects.  Namely
https://gerrit-int.chromium.org/#change,16528.  Could you put the retry messages
to stderr? 

We want to be able to call gsutil and close stderr and get only objects that
exist, or have it return empty.


On 2012/04/17 09:19:14, cmp wrote:
> lgtm
> 
> I recall implementing something similar using output processors in threads and
> found that the threads themselves introduced timing issues that caused
> stdout+stderr to be printed erratically between separate calls to the wrapper.

> I assume you know that already, just noting here for posterity.
> 
> Since this patch changes the way that output is handled for all platforms (and
> could affect how well this works at all in some or all places), when you land
it
> please keep an eye on the codesearch bot's upload, and chromium.perf's win
> release upload and download (upload on Win Builder, download on XP Perf 1, for
> example).