Mongrel users - Sep 2007 - memcached and fragment storage, session storage with a mongrel cluster

Greetings,

I posted this not on the Rails mailing list and didn''t get a definitive
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 appreciated.

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
development.rb:

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 for
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 thing.

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 a
couple of mongrel instances via mongrel cluster on a fedora core 5
box.   It seems as if a memcache pool is being created for each
mongrel instance, instead of the app.  Is there some other kind of
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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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:
http://www.texperts.com/2007/05/01/race-conditions-in-rails-sessions-and
-how-to-fix-them/
 
--TR 


________________________________

	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
	
	
	Greetings,

	I posted this not on the Rails mailing list and didn''t get a
definitive 
	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
appreciated.
	
	
	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
	development.rb:

	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
for
	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
thing.

	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
a
	couple of mongrel instances via mongrel cluster on a fedora core
5
	box.   It seems as if a memcache pool is being created for each
	mongrel instance, instead of the app.  Is there some other kind
of
	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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Thanks, Terry.  That''s very helpful.


On Sep 7, 2007, at 4:01 PM, Reese, Terry wrote:
> 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: http://www.texperts.com/ 
> 2007/05/01/race-conditions-in-rails-sessions-and-how-to-fix-them/
>
> --TR
>
> 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
>
> Greetings,
>
> I posted this not on the Rails mailing list and didn''t get a  
> definitive
> 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 appreciated.
>
> 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
> development.rb:
>
> 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 for
> 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 thing.
>
> 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 a
> couple of mongrel instances via mongrel cluster on a fedora core 5
> box.   It seems as if a memcache pool is being created for each
> mongrel instance, instead of the app.  Is there some other kind of
> config I need to do in production.rb?  The stuff I''ve found via
> googling seems to apply to Rails < 1.2
>
> Thanks much
>
> _______________________________________________
> Mongrel-users mailing list
> Mongrel-users at rubyforge.org
> http://rubyforge.org/mailman/listinfo/mongrel-users
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