5% of the visitors page requests are resulting in 500 internal server error

After upgrading to Evo 1.02 about 5% of the visitors page requests are resulting in a 500 internal server error.
But its a random problem, and when making a page refresh, the error are gone, and the page are showing up normally.

The problem are the same in the manager... And there are no logic at all in which templates, snippets etc, the pages are using.

The site are running on a shared host, and - yet - without - any logfiles. (But I have requested them).
PHP Version 5.3.0 CGI/FastCGI
MySql version 5.0.32
Apache version 2.2.3

PHP are running with register_globals and safe_mode = Off, and with Suhosin Patch 0.9.7

Are there anybody who have a answer - and even better - a solution? I have a theori about some kind of timing problem, but can’t figure out where.

Quote from: Henrik at Nov 15, 2009, 10:15 AM

After upgrading to Evo 1.02 about 5% of the visitors page requests are resulting in a 500 internal server error.
But its a random problem, and when making a page refresh, the error are gone, and the page are showing up normally.

That sounds to me like the errors are occurring only if the page is being cached, i.e. first access after the page caches are cleared. Have you checked the event log in the manager? It could be a plugin that is only firing when the page is being cached or a cached snippet that is only executing on the first access to a page.

There are 3 types of pages where the 2 of them are cached and 1 are not. But there are no pattern in which template the page are using, and the problem.

The event log are empty.

I’ve tried to empty the cashe from the manager, but without any change.

After that I have re-read Jason’s answer, I had changed the snippet calls in the template there are un-cashed to be un-cashed. But still without any luck.

It could be any snippet or plugin causing a 500 error to be triggered then; try disabling them one at a time, especially any that would be common to your affected pages.

It could also possibly be JS errors or invalid markup, so make sure that is solid as well.

I’ve checked the templates, deactivated the snippets, and the plugins. And checked the logfiles, all without any luck.

Then I checked the permissions on the files and folders, re-installed modx, made at db upgrade, moved the site to another server at the same host, still no luck.

Played around with the php.ini and got a performance boost, but still got the 500-errors.

The last solution was a downgrade to php 5.2.11, and now the 500-errors are gone. (And now I got a little more happy customer).

I have made a copy of the site, on the same server and on php 5.3 to see if I can track the errors down. And if I (or the host) get the real solution, I will post it here.

But Jason: Thanks for your suggestions!