WordPress MU

I'm scratching my head here... Has anyone seen this before?

My MU blog (2.6.3) has been running fine for several weeks, and all of a sudden, any page dynamically generated was coming up blank. Nothing was getting logged in the error log. The server was not under heavy load, and nothing looked out of the ordinary -- Apache and PHP worked fine on other sites on the same server.

Restarting Apache fixed it.

A bunch of things have run through my mind as possibilities, but none of them seem to make a lot of sense to me. For example, I at first figured it was an issue with WP Super Cache, except that it ran for _weeks_ with no errors, and it works fine now that Apache has been restarted. I also thought it might have been a problem with APC, but other PHP/APC sites on the server were working fine, which also rules out resource starvation.

I'm back up and running, I'm just trying to figure out what could have happened.

I had this happen as well, but only at domain/com/wp-admin/
It did not redirect and just went blank (very annoying when you try to edit a post :-P )

Aalso Apache restarts helped, but only for a while. I was changing hosts anyway as slhost has been going down the drain ever since they sold out (server outages, slow, DNs problems). Now I am at my new host and voila! No more white pages.

So maybe some server settings, DNS errors? Or crappy host?

Just my 2cts..
Cheers,
Bike

Standard Apache settings allow 150 simultanious connections. If you're 151-st - you'll get locked :)
So if your WPMU website is busy - this is what might happen.

The other thing I would look at is MySQL slow log.

I run the server, so I can't blame a crappy host. (Except for when they're offline...)

I definitely didn't have 150 simultaneous connections; with the volume of traffic I had, I'd be lucky if I had 5 simultaneous connections. The Apache log shows that nothing was out of the ordinary at the time, so there was definitely not a surge in traffic. (Plus, it was consistently happening until I restarted Apache, but only on pages generated by WP, never on any static pages or on non-WP dynamic sites.)

I don't have the slow query log on right now. I don't think that would be it, though, because it was pretty much instantly serving up a blank page, versus eventually timing out.

OK, guessing further :)

Does your OS logs tell you anything regarding apache service?
Would be good to know what OS and what version of apache you're using.

Also, check if tmp is not full. It causes all kinds of issues :)

I would try asking over at webhostingtalk.com since there are a lot more people that administer servers there. It's definitely a server issue. One thing you should check is if you're hitting RAM limits. Type this in shell and look for any fails:
cat /proc/user_beancounters

Sorry to bump an old thread, but it happened again today. The server was under no load at all:

new:~# uptime && free
20:56:14 up 48 days, 5:17, 2 users, load average: 0.07, 0.03, 0.01
total used free shared buffers cached
Mem: 524464 505756 18708 0 20320 102008
-/+ buffers/cache: 383428 141036
Swap: 0 0 0

The thing is that everything else on the server works fine. I have a few other PHP-hosted sites I run on the same server, in the same Apache instance, which carry on, speedy as ever. The _only_ thing that doesn't work is pages generated by WordPress.

I'm running Debian (Etch); Apache's exact string is "Apache/2.2.3 (Debian) DAV/2 PHP/5.2.0-8+etch13 mod_ssl/2.2.3 OpenSSL/0.9.8c"

The one maybe-special thing is APC, but uber-default, at 3.0.19. I also use WP Super Cache. But both are rock-solid until pages suddenly start coming up blank, including the admin panel, so nothing's apparent. The server hasn't been under heavy load either time, and both times it's gone weeks, if not months, with nary a problem.

Loading /wp-admin/, it came up blank (like all the other pgaes), and just shows an HTTP 200 for the page in access_log. Nothing in error_log.

Once again, restarting Apache cured it.

I don't have a /proc/user_beancounters (I'm on Xen not Virtuozzo), but the graphs I keep of memory usage show that it's been pretty flat all week, with nothing out of ordinary when it failed or when I restarted Apache.

The blank page loads instantly, not a timeout, and I get no errors logged anywhere. My only guess is that it's a caching problem, either in APC or WP SuperCache, but neither is giving me any actual indications.

OK, try turning off caching completely. Give your system a test-drive for some time and check if this still appears.