Question

We’ve recently enabled APC on our servers, and occasionally when we publish new code or changes we discover that the source files that were changed start throwing errors that aren’t reflected in the code, usually parse errors describing a token that doesn’t exist. We have verified this by running php -l on the files the error logs say are affected. Usually a republish fixes the problem. We’re using PHP 5.2.0 and APC 3.01.9. My question is, has anyone else experienced this problem, or does anyone recognize what our problem is? If so, how did you fix it or how could we fix it?

Edit: I should probably add in some details about our publishing process. The content is being pushed to the production servers via rsync from a staging server. We enabled apc.stat_ctime because it said this helps things run smoother with rsync. apc.write_lock is on by default and we haven’t disabled it. Ditto for apc.file_update_protection.

Answer 1

Sounds like a part-published file is being read and cached as broken. apc.file_update_protection is designed to help stop this.

in php.ini: apc.file_update_protection integer

apc.file_update_protection setting
puts a delay on caching brand new
files. The default is 2 seconds which
means that if the modification
timestamp (mtime) on a file shows that
it is less than 2 seconds old when it
is accessed, it will not be cached.
The unfortunate person who accessed
this half-written file will still see
weirdness, but at least it won’t
persist.

Following the question being edited: One reason I don’t see these kinds of problems is that I push a whole new copy of the site (with SVN export). Only after that is fully completed does it become visable to Apache/Mod_php (see my answer How to get started deploying PHP applications from a subversion repository? )

The other thing that may happen of course, is that if you are updating in place, you may be updating files that depend on others that have not yet been uploaded. Rsync can only guarantee atomic updates for individual files, not the entire collection that is being changed/uploaded. Another reason I think to upload the site en-mass, and only then put into use.