(pylibmc) cache.set() hangs

[fahhem]

My setup is a localhost memcached server on the default port:

CACHES = {
    'default': {
        'BACKEND':'django.core.cache.backends.memcached.PyLibMCCache',
        'LOCATION':'127.0.0.1:11211',
    }
}

When the backend changes to MemcachedCache, the problem goes away so this is definitely pylibmc. I did this exact setup on two different projects and two separate machines over the span of the last two weeks and I ran into this same problem both times:

When using cache.set(key,value,timeout), some keys will hang the thread/process when served through Apache (v2.2.16-1ubuntu3.1). When using ./manage.py runserver or runserver_plus, cache.set() works and when I switch from runserver to apache it works fine because cache.get() gets the value and no cache.set() is called. When the timeout passes, apache again hangs at the same cache.set(). I used a ton of logging.error() calls to find where apache hangs.

This machine is Ubuntu but the first machine with the problem was a Debian machine, both are running mostly stable, with a few non-critical packages from testing. Both run python2.6 and django 1.3, the first machine was 1.3-beta-1, this one had the problem in both beta and rc.

[Ludvig Ericson]

• Which version of pylibmc?
• Which version of libmemcached?
• What are you trying to set, a string, a complex type, ...?
• Do all sets cause this behavior, i.e. is it reproducible?
• What is your Apache configuration, how are you even running Django - mod_wsgi? If so, under what parameters?

Answer these questions, and do so on ​http://github.com/lericson/pylibmc/issues - this has nothing to do with Django, as you so aptly pointed out.

[Ludvig Ericson]

And in hindsight, my reply might seem a bit arrogant - sorry for that, you obviously took some time to make this ticket. However, for me to help you I need you to follow the above instructions.

[fahhem]

I should probably have done so, but I didn't know what cache.set() translates to for pylibmc so I'll look that up and redo this ticket in the right place.