APC caching different files with same names in different directories as same file

Question

I'm having trouble with my APC config. It seems like APC caches files with the same name, in different directories, as if they were the same file.

The directory structure is as follows:

src/ development/ edge/ stable/ tag-20101101/ tag-20101115/ ... 

The code resides in development, edge and in each of the tag directories. What seems to happen is that when APC caches for example src/stable/foo/bar/quux.php, it uses the same cache for src/development/foo/bar/quux.php, even though they're not the same file. Some files may be included using a relative path, though I have not yet determined if there is any connection between files included relatively, and the APC caching problems.

My APC config (as reported by apc.php) is as follows:

apc.cache_by_default 1 apc.canonicalize 1 apc.coredump_unmap 0 apc.enable_cli 0 apc.enabled 1 apc.file_md5 0 apc.file_update_protection 2 apc.filters apc.gc_ttl 3600 apc.include_once_override 0 apc.lazy_classes 0 apc.lazy_functions 0 apc.max_file_size 5M apc.mmap_file_mask /tmp/apc.tKRzKb apc.num_files_hint 1000 apc.preload_path apc.report_autofilter 0 apc.rfc1867 0 apc.rfc1867_freq 0 apc.rfc1867_name APC_UPLOAD_PROGRESS apc.rfc1867_prefix upload_ apc.rfc1867_ttl 3600 apc.shm_segments 1 apc.shm_size 128 apc.stat 1 apc.stat_ctime 0 apc.ttl 0 apc.use_request_time 1 apc.user_entries_hint 4096 apc.user_ttl 0 apc.write_lock 1 

I am using PHP 5.3.2, and APC 3.1.3p1, with PHP-FPM. The server is a virtualized RHEL 5.4 with 4GB of allocated RAM, running on another RHEL 5.4 server with 32 GB RAM and 12 AMD Opteron 2.4 GHz CPU cores.

Does anyone have any idea what could cause this, or anything I might do to fix it?

Answer 1

according to the docs the paths can be canonicalized when in no stat mode.

http://php.net/manual/en/apc.configuration.php

I interpret that as it may work if you change apc.stat to 0 in the above configuration.

//John

Answer 2

Turned out that the problem wasn't due to APC, but because the NFS3 NAS hosting the code was mounted as NFS4. This caused an issue with filesystem caching. Using APC to an extent masked the actual issue.

Thanks for your time, though.