Error logs on chromeos-server12:

[Sun Oct 08 06:25:15.768545 2017] [mpm_event:notice] [pid 25985:tid 140004364748672] AH00489: Apache/2.4.10 (Ubuntu) mod_wsgi/3.4 Python/2.7.6 configured -- resuming normal operations
[Sun Oct 08 06:25:15.770735 2017] [core:notice] [pid 25985:tid 140004364748672] AH00094: Command line: '/usr/sbin/apache2'
[Sun Oct 08 12:44:59.742752 2017] [mpm_event:notice] [pid 25985:tid 140004364748672] AH00491: caught SIGTERM, shutting down
[Sun Oct 08 12:45:02.516989 2017] [mpm_event:notice] [pid 10707:tid 139660605253504] AH00489: Apache/2.4.10 (Ubuntu) mod_wsgi/3.4 Python/2.7.6 configured -- resuming normal operations
[Sun Oct 08 12:45:02.517174 2017] [core:notice] [pid 10707:tid 139660605253504] AH00094: Command line: '/usr/sbin/apache2'
[Mon Oct 09 06:19:57.274403 2017] [:error] [pid 18103:tid 139660482262784] DEBUG:root:<class 'urllib2.HTTPError'>(HTTP Error 500: INTERNAL SERVER ERROR)
[Mon Oct 09 06:19:57.274749 2017] [:error] [pid 18103:tid 139660482262784] DEBUG:root:Retrying in 10.000000 (10.000000 + jitter 0.000000) seconds ...
[Mon Oct 09 06:20:04.742222 2017] [:error] [pid 3960:tid 139660482262784] DEBUG:root:<class 'urllib2.HTTPError'>(HTTP Error 500: INTERNAL SERVER ERROR)
[Mon Oct 09 06:20:04.742537 2017] [:error] [pid 3960:tid 139660482262784] DEBUG:root:Retrying in 10.000000 (10.000000 + jitter 0.000000) seconds ...
[Mon Oct 09 06:20:07.383236 2017] [:error] [pid 18103:tid 139660482262784] DEBUG:root:<class 'urllib2.HTTPError'>(HTTP Error 500: INTERNAL SERVER ERROR)
[Mon Oct 09 06:20:07.383358 2017] [:error] [pid 18103:tid 139660482262784] DEBUG:root:Retrying in 20.000000 (20.000000 + jitter 0.000000) seconds ...
[Mon Oct 09 06:20:14.847360 2017] [:error] [pid 3960:tid 139660482262784] DEBUG:root:<class 'urllib2.HTTPError'>(HTTP Error 500: INTERNAL SERVER ERROR)

...

[Mon Oct 09 07:20:48.787074 2017] [core:notice] [pid 10707:tid 139660605253504] AH00052: child pid 10787 exit signal Segmentation fault (11)
[Mon Oct 09 07:20:59.416548 2017] [:error] [pid 28284:tid 139660482262784] [remote 127.0.0.1:61244] mod_wsgi (pid=28284): Exception occurred processing WSGI script '/usr/local/autotest/frontend/frontend.wsgi'.
[Mon Oct 09 07:20:59.416765 2017] [:error] [pid 28284:tid 139660482262784] [remote 127.0.0.1:61244] IOError: failed to write data
[Mon Oct 09 07:23:16.135524 2017] [:error] [pid 12612:tid 139660482262784] [remote 127.0.0.1:61244] mod_wsgi (pid=12612): Exception occurred processing WSGI script '/usr/local/autotest/frontend/frontend.wsgi'.
[Mon Oct 09 07:23:16.135682 2017] [:error] [pid 12612:tid 139660482262784] [remote 127.0.0.1:61244] IOError: failed to write data
[Mon Oct 09 07:23:24.514185 2017] [:error] [pid 24438:tid 139660482262784] [remote 127.0.0.1:61244] mod_wsgi (pid=24438): Exception occurred processing WSGI script '/usr/local/autotest/frontend/frontend.wsgi'.
[Mon Oct 09 07:23:24.514332 2017] [:error] [pid 24438:tid 139660482262784] [remote 127.0.0.1:61244] IOError: failed to write data
[Mon Oct 09 07:24:14.035233 2017] [core:notice] [pid 10707:tid 139660605253504] AH00052: child pid 31678 exit signal Segmentation fault (11)
[Mon Oct 09 07:24:35.989742 2017] [:error] [pid 31305:tid 139660482262784] [remote 127.0.0.1:61244] mod_wsgi (pid=31305): Exception occurred processing WSGI script '/usr/local/autotest/frontend/frontend.wsgi'.
[Mon Oct 09 07:24:35.989899 2017] [:error] [pid 31305:tid 139660482262784] [remote 127.0.0.1:61244] IOError: failed to write data
[Mon Oct 09 07:25:33.750179 2017] [:error] [pid 22368:tid 139660482254592] [remote 127.0.0.1:60988] mod_wsgi (pid=22368): Exception occurred processing WSGI script '/usr/local/autotest/frontend/frontend.wsgi'.
[Mon Oct 09 07:25:33.750332 2017] [:error] [pid 22368:tid 139660482254592] [remote 127.0.0.1:60988] IOError: failed to write data
[Mon Oct 09 07:25:38.588336 2017] [:error] [pid 30693:tid 139660482262784] [remote 127.0.0.1:61244] mod_wsgi (pid=30693): Exception occurred processing WSGI script '/usr/local/autotest/frontend/frontend.wsgi'.
[Mon Oct 09 07:25:38.588481 2017] [:error] [pid 30693:tid 139660482262784] [remote 127.0.0.1:61244] IOError: failed to write data
[Mon Oct 09 07:25:53.712381 2017] [:error] [pid 17679:tid 139660482254592] [remote 127.0.0.1:60988] mod_wsgi (pid=17679): Exception occurred processing WSGI script '/usr/local/autotest/frontend/frontend.wsgi'.
[Mon Oct 09 07:25:53.712534 2017] [:error] [pid 17679:tid 139660482254592] [remote 127.0.0.1:60988] IOError: failed to write data
[Mon Oct 09 07:26:07.416638 2017] [:error] [pid 10251:tid 139660482254592] [remote 127.0.0.1:60988] mod_wsgi (pid=10251): Exception occurred processing WSGI script '/usr/local/autotest/frontend/frontend.wsgi'.
[Mon Oct 09 07:26:07.416784 2017] [:error] [pid 10251:tid 139660482254592] [remote 127.0.0.1:60988] IOError: failed to write data
[Mon Oct 09 10:58:06.963648 2017] [mpm_event:notice] [pid 10707:tid 139660605253504] AH00491: caught SIGTERM, shutting down


Notice the seg faults every few minutes. They'd been happening for a while, then stopped for a couple of hours before the server was stopped. The server did continue to process requests during that ~2.5 hour gap in the error log.