Aaron, could you make a recommendation here? You don't necessarily need to be the one to fix this, but I'd like to get your take before having someone run off and do it.

2013-09-05 21:18:07 mw1160 commonswiki: thumbnail failed on mw1160: error 137 "" from "'/usr/bin/convert' -quality 80 -background white -define jpeg:size=8192x5145 '/tmp/localcopy_72e5b84ae821-1.jpg' -thumbnail '8192x5145!' -set comment 'File source: http://commons.wikimedia.org/wiki/File:Sandro_Botticelli_-_La_nascita_di_Venere_-_Google_Art_Project_-_edited.jpg' -depth 8 -sharpen '0x0.8' -rotate -0 '/tmp/transform_32eba68e9459-1.jpg' 2>&1"

^ That's already in the thumbnail logs. Are you wanting more than that?

limit.sh currently has the line:

if ! mkdir -m 0700 "$MW_CGROUP"/$$; then
        echo "limit.sh: failed to create the cgroup." 1>&2
        exit 1
fi

Given that we use php passthru and throw away stderr, I think it might make sense just to output that to stdout (Or possibly output it to both stdout and stderr).

Change 83974 had a related patch set uploaded by Brian Wolff:
Add way of including all stderr output when executing command

https://gerrit.wikimedia.org/r/83974

Just to clarify the situation here:

We currently output to the log:

sprintf( 'thumbnail failed on %s: error %d "%s" from "%s"',
                wfHostname(), $retval, trim( $err ), $cmd ) );

Where $err is the stdout and stderr from convert. However it does not include the stderr from limit.sh. https://gerrit.wikimedia.org/r/83974 would change this to include the stdout and stderr from limit.sh and the actual command executed.

Change 83974 merged by jenkins-bot:
Add way of including all stderr output when executing command

https://gerrit.wikimedia.org/r/83974