I have an unusual problem that is hard to nail down to a specific cause.
I'm running a WordPress website on PHP 5.6, IIS 8.5 and Windows Server 2012 RT2
In the past and more frequently this week, the website has been going down with a PHP white screen of death for up to an hour, sometimes more. Stopping and then restarting the AppPool fixes the issue.
During the outage the PHP error log states that WordPress is unable to require_once various PHP files (it cannot find them). The script it complains about changes, sometimes even 2 or 3 times during the outage. The files definitely exist.
Sample:
[26-Aug-2015 22:27:44 UTC] PHP Warning: require_once(C:\**hidden**\content\plugin): failed to open stream: No such file or directory in C:\**hidden**\content\plugins\all-in-one-seo-pack\all_in_one_seo_pack.php on line 156
[26-Aug-2015 22:27:44 UTC] PHP Fatal error: require_once(): Failed opening required 'C:\**hidden**\content\plugins\all-in-one-seo-pack/aioseop_functions.php' (include_path='.;C:\php\pear') in C:\**hidden**\content\plugins\all-in-one-seo-pack\all_in_one_seo_pack.php on line 156
Correlating to the time of the outage, the IIS event log lists the following:
*(hidden)* 5138 Warning Microsoft-Windows-WAS System 27/8/2015 8:27:58 AM
A worker process '4696' serving application pool 'Website' failed to stop a listener channel for protocol 'http' in the allotted time. The data field contains the error number.
*(hidden)* 5013 Warning Microsoft-Windows-WAS System 27/8/2015 8:27:58 AM
A process serving application pool 'Website' exceeded time limits during shut down. The process id was '4696'.
The following discussion touches on a similar issue, but alas no solution. I haven't anything else that accurately relates to my specific issue. http://forums.asp.net/t/2052328.aspx?IIS+Warning+Event+ID+5138+followed+by+event+ID+warning+5013
It may have something to do with recycling the AppPool, but I can't reliably reproduce the problem. It is random and intermittent. Please offer some advice.
Update:
The IIS errors 5138 and 5013 are not often present during an outage. The PHP errors always are.
These outages appear to happen more frequently during out of office times. Some instances appear around roughly the same time, but others do not.
