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blank white page of death

Started by badon, August 06, 2014, 05:20:15 PM

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badon

I need some help troubleshooting a blank white page being returned from this SMF 1.1.18 page:

https://www.livebusinesschat.com/smf/index.php?topic=5632.160

Another link to the original post that preceded the problem, on the same page with the same blank result:

https://www.livebusinesschat.com/smf/index.php?topic=5632.msg37918;topicseen#msg37918

I noticed the moment it happened when a user posted a reply with an attachment. Although I can't view the reply, the post text does appear in a post preview, where the user mentions attaching an image to the post. So far, I've tried using these maintenance features:

* Find and repair any errors.
* Optimize all tables to improve performance.
* Recount all forum totals and statistics.

I've also tried viewing the source code of the page, but it's a single empty line, with no error message of any kind. I've checked it from different network locations with different browsers, but the result is the same. Ideas?

margarett

You should update to 1.1.19 as that's a security release (in fact, you should plan an upgrade for 2.0.x ;) )

About that issue: a white page is usually a php error so you need to check your server logs for further info. Do note, not SMF log --> php error log ;)
Se forem conduzir, não bebam. Se forem beber... CHAMEM-ME!!!! :D

QuoteOver 90% of all computer problems can be traced back to the interface between the keyboard and the chair

badon

For some reason, I'm not able to do the convenient install like I can with my 2.0.x forum. The 1.1.18 forum can't connect to check for an update, and I'm not sure why. I can do a manual upgrade to 1.1.19, but I'm nervous about that when there's an outstanding problem with an unknown cause. Our system is FreeBSD, and I could find no PHP errors with this:

tail -f /var/log/httpd-error.log

I forgot to mention that my test posting went through after the one by ggoodluck2013 that preceded the blank page problem, even though I wasn't able to view it. It shows up in a post preview ("test") and on the forum recent posts index:

https://www.livebusinesschat.com/smf/index.php

Any other ideas?

badon

Internet Explorer reports "HTTP 500 Internal Server Error". I guess Firefox and Google Chrome aren't smart enough to do that. Still, there are no related errors in /var/log/httpd-error.log, which seems odd, unless I'm looking in the wrong place, or IE is wrong.

margarett

httpd should be Apache's log. You need to find PHP's log. Check in php.ini for its location ;)
Se forem conduzir, não bebam. Se forem beber... CHAMEM-ME!!!! :D

QuoteOver 90% of all computer problems can be traced back to the interface between the keyboard and the chair

badon

error_log is commented out in php.ini, but there ARE PHP errors recorded in httpd-error.log, just not anything important or related to SMF. They're mostly warning about undefined or unused variables in another script. I'm not sure if php.ini is configured to use httpd-error.log, or if it's simply not logging what we want it to be logging, and thus I should enable it. What do you think?

In any case, this seems odd to happen suddenly like this. One cause of this problem in the past was a bad injection of malicious code into SMF, but since this only affects one single page on the forum (that I know of), I'm skeptical of that.

margarett

Only one way to find out ;) Uncomment it, set a valid location, save and restart Apache ;) Check if the file is created when the white page appears.
Se forem conduzir, não bebam. Se forem beber... CHAMEM-ME!!!! :D

QuoteOver 90% of all computer problems can be traced back to the interface between the keyboard and the chair

badon

I edited this:

/usr/local/etc/php.ini

to have this line:

error_log = /var/log/php-error.log

...and then I restarted apache with this:

/usr/local/sbin/apachectl -k graceful

Then I reloaded the problem page, and checked to see if /var/log/php-error.log was created, but it was not. Does that rule this out as a PHP problem?

badon

I tried making another test post in a different location, and it did not result in a blank page. I have the impression that this is an isolated problem that is less likely to be connected a more systemic PHP problem, especially considering its sudden recent appearance.

badon

I split out the last viewable message and all following messages, and moved them here temporarily:

https://www.livebusinesschat.com/smf/index.php?topic=5705.0

They are still unviewable there, but at least the main topic is working again until someone figures out what's wrong and how to fix it. If it's truly isolated, then maybe it's from a random cosmic ray flipping a bit somewhere, or something like that. Our system is triple-mirrored ZFS RAID, which is resilient to that kind of problem AFTER the data is successfully written to the disk. Before it gets written to the disk, it's in memory somewhere, and ZFS can't correct that kind of an error.

The interesting thing is the error would have had to occur with perfect timing in order to affect only a single post. Maybe I'll take a look at the raw database text eventually to see if I can see anything obviously wrong with it.

kat


badon

No further errors have come to my attention, so with only a single post affected, I'm inclined to believe this problem was caused by an extremely rare memory corruption event. We use ECC RAM, so for the error to get past the error correction algorithm too is highly unusual (though not impossible, obviously). I haven't bothered to look at the raw database text yet, but I will next time I back it up prior to upgrading. Then, I might have more info about what happened.

kat

Fingers crossed, then. :)

I'll mark this as having been solved, for now. If this problem rears it's ugly head, again, just mark it "Not solved" and we'll see what we can figure out. :)

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