[Mongrel] memcached and fragment storage, session storage with a mongrel cluster

Reese, Terry terry.reese at oregonstate.edu
Fri Sep 7 16:01:03 EDT 2007

So we had some similar problems related to running our rails application
using either memcache or an sql-based sessioning solution using a number
of mongrels with Apache's balancer.  In the end, I think the problem we
had was related to a race condition when setting session data between
ajax calls.  On the rails trac instance, there has been a plugin
developed for these types of conditions called smartsessionstore.  It
works with the sql_session plugin, meaning your sessioning will be sql
based so not quite as fast as memcache, but I'm not sure if the
difference is actually noticable to users.  Here's the link:


	From: mongrel-users-bounces at rubyforge.org
[mailto:mongrel-users-bounces at rubyforge.org] On Behalf Of cleaner416
	Sent: Friday, September 07, 2007 10:37 AM
	To: mongrel-users at rubyforge.org
	Subject: [Mongrel] memcached and fragment storage,session
storage with a mongrel cluster

	I posted this not on the Rails mailing list and didn't get a
	response so I thought I'd post it here, since I figure lots of
you are using
	mongrel with Rails apps. Any suggestions would be greatly
	I've been using file-based fragment caching and DB-based session
	caching quite extensively.  I decided to try out memcached for
both to
	see if I could achieve a meaningful performance gain for a
particular app.

	I searched around a bit and simply added two lines to my

	config.action_controller.fragment_cache_store = :mem_cache_store
	config.action_controller.session_store = :mem_cache_store

	(I also changed config.action_controller.perform_caching = true
	testing )

	This works like a charm on my development box.  (Mac) I've got
memcached -vv
	running in another terminal window I can see it doing it's

	However, as soon as I tried this on my production box, (by
adding the
	above lines to production.rb) I ran into some odd problems.   My
	production setup is pretty vanilla: Apache 2.2 load balancing to
	couple of mongrel instances via mongrel cluster on a fedora core
	box.   It seems as if a memcache pool is being created for each
	mongrel instance, instead of the app.  Is there some other kind
	config I need to do in production.rb?  The stuff I've found via
	googling seems to apply to Rails < 1.2

	Thanks much

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