[Buildbot-devel] Unclean shutdown of buildbot followed by another build with the same number results in mismatched text output for the build

[Brandon Ehle]

I've seen a problem in a few instances where incorrect build output is
making it into the stdio log from one of the build steps.

I think I've narrowed the problem down to:

1) build with the old version of the master config file
2) ctrl-c the buildbot master on windows to make it exit
3) change the master config file for a step
4) start buildbot master again
5) issue a new build

In some cases the buildbot shutdown seems to be forgetting some of the
revisions across a restart, thus when its writing logs from new builds
sometimes it has both compressed and non-compressed stdio logs.  For
instance the directory tree when the problem happened looked like this
for me:

0-log-MasterShellCommand-stdio
0-log-compile-stdio.bz2
0-log-shell-stdio.bz2
0-log-shell_1-stdio.bz2
0-log-shell_2-stdio.bz2
0-log-shell_3-stdio
0-log-shell_3-stdio.bz2
0-log-shell_4-stdio.bz2
0-log-shell_5-stdio.bz2
0-log-svn-studio.bz2

Notice that there is both an uncompressed version of the log for
shell_3 and an uncompressed version.  One of those files was written
on the build before the buildbot master restarts and the second log
file was written after the reboot.

In the cases where the webpage is reporting the incorrect stdio output
for the build, it seems to pulling from the compressed log instead of
the newly written uncompressed log.

I can think of a couple of ways to try and fix this, but I'm also
curious as to why the buildbot master seems to be forgetting builds
upon restarting.