File based cache not very efficient with large amounts of cached files

[anteater_sa]

When using the file based cache having a large number of cached pages (in my case over 100,000) makes the system inefficient as there is a function in django.core.cache.backends.filebased called _get_num_entries which actually walks through the cache direcotry structure counting files.

Maybe setting max_entries to 0 in the settings file could mean unlimited cached files, then the _get_num_entries function could be as follows:

    def _get_num_entries(self):
        count = 0
        if max_entries == 0: return count # Don't count files if max_entries is set to 0
        return count
        for _,_,files in os.walk(self._dir):
            count += len(files)
        return count
    _num_entries = property(_get_num_entries)

[anteater_sa]

sorry, should be as follows:

    def _get_num_entries(self):
        count = 0
        if max_entries == 0: return count # Don't count files if max_entries is set to 0
        for _,_,files in os.walk(self._dir):
            count += len(files)
        return count
    _num_entries = property(_get_num_entries)

[dc]

1.1 is at a feature freeze right now so moving to 1.2.

[John Moylan]

I've been bitten by this also.
My fix is to return count while it is still 0 and manage the cache myself using a daily cron job.

It would be nice if Django allowed me to disable the filebased cache management feature using settings.py.

[josh]

Patch that fixes issue

[josh]

Opps, made a mistake with the first patch.

[josh]

Just to explain the patch...

If you pass 'max_entries=0' no culling of the cache will ever occur.
If number of entries is less than 'max_entries' then culling will be performed.

[Russell Keith-Magee]

I'm going to wontfix, on the grounds that the filesystem cache is intended as an easy way to test caching, not as a serious caching strategy. The default cache size and the cull strategy implemented by the file cache should make that obvious.

If you need a cache capable of holding 100000 items, I strongly recommend you look at memcache. If you insist on using the filesystem as a cache, it isn't hard to subclass and extend the existing cache.

[John Moylan]

Are you saying that file based cache is not suitable for production? File based cache is more suitable for some scenarios than memcache.

I use file caching to cache processed JPG's. Memcache is not as capable for such a scenario.

[anteater_sa]

I have Django sites of tens of thousands of pages running for over 2 years using the above patches, so your statements about filesystem caching not a serious strategy are irrelevant. Also, filesystem caching is not comparable to memcaching, they solve two completely different problems.

[Jacob]

Milestone 1.2 deleted

[Grant Jenks]

I had the same problem but a couple more requirements. For future readers, I want to mention the DiskCache (​http://www.grantjenks.com/docs/diskcache/) project. DiskCache is an Apache2 licensed disk and file backed cache library, written in pure-Python, and compatible with Django. There are no dependencies outside the standard library (no managing other processes) and it's efficient enough to handle cache evictions during the request/response cycle (no cron job necessary).

[Mateusz Konieczny]

#29994 proposes documenting this performance issues.