Mongrel users - Jan 2007 - Most reliable setup for mongrel

I''m looking for the most reliable setup for Mongrel.  Reliable meaning
avoiding things like sending too many requests to a single mongrel
process, or sending requests to a mongrel process that has hung for
some reason.  The handler will most likely be rails, but it might be a
custom handler.  SSL is also a requirement, which limits the options a
bit but it can''t be done away with.

I spent some time looking at using the proxy balancer in apache, and
it appears that the balancer can pile up requests on mongrel because
there is no way to tell apache to not send more than one request at a
time to any single balance member.  I''m also not sure how well things
are handled if a mongrel process hangs in some way.  Not that it would
of course:)

Suggestions?

Chris

On Jan 25, 2007, at 10:24 PM, snacktime wrote:
> I''m looking for the most reliable setup for Mongrel.  Reliable
meaning
> avoiding things like sending too many requests to a single mongrel
> process, or sending requests to a mongrel process that has hung for
> some reason.  The handler will most likely be rails, but it might be a
> custom handler.  SSL is also a requirement, which limits the options a
> bit but it can''t be done away with.
>
> I spent some time looking at using the proxy balancer in apache, and
> it appears that the balancer can pile up requests on mongrel because
> there is no way to tell apache to not send more than one request at a
> time to any single balance member.  I''m also not sure how well
things
> are handled if a mongrel process hangs in some way.  Not that it would
> of course:)
>
> Suggestions?
>
> Chris

Chris-

	Haproxy is a software proxy that can do the right thing and not  
overload mongrels. But it is not a webserver. I have used it behind  
nginx. So nginx or apache proxy to one haproxy and then haproxy does  
the load balancing in a more inteligent way then apapche ro nginx can  
do right now.

	But Igor the author of nginx said that he will be adding a max-load  
to the ngixn proxy module which you could set to one and then ngxin  
would queue requests instead of mongrel and only send requests to  
mongrels that are not busy. This will be the best option with the  
least moving parts once he adds this feature.

Cheers-
-- Ezra Zygmuntowicz 
-- Lead Rails Evangelist
-- ez at engineyard.com
-- Engine Yard, Serious Rails Hosting
-- (866) 518-YARD (9273)

Hi Chris,
  The optimal solution depends on the resources you have available to
you. Assuming you would like to accomplish your objectives "on a
shoestring" I would recommend looking into, as Ezra suggested, HAProxy
(HAProxy does not support SSL). HAProxy knows how to be smart about
what''s going on in the backend. I have configured HAProxy in front of
nginx web/application servers with mongrels. If the requested server
is not available, the request is handled by an available server.

HAProxy->(nginx/mongrels)->db

[ load balancer->app servers->db servers ]

To add to Ezra''s suggestion, please keep in mind that HAProxy does not
support SSL. I use Pound to handle SSL requests, routing them to the
appropriate web/application servers.

Add to that virtualization and you have a scalable solution on a shoestring ;)

PS: Thanks Zed for your excellent work on mongrel.

Best,
Rod

On 1/25/07, Ezra Zygmuntowicz <ezmobius at gmail.com>
wrote:
>
> On Jan 25, 2007, at 10:24 PM, snacktime wrote:
>
> > I''m looking for the most reliable setup for Mongrel. 
Reliable meaning
> > avoiding things like sending too many requests to a single mongrel
> > process, or sending requests to a mongrel process that has hung for
> > some reason.  The handler will most likely be rails, but it might be a
> > custom handler.  SSL is also a requirement, which limits the options a
> > bit but it can''t be done away with.
> >
> > I spent some time looking at using the proxy balancer in apache, and
> > it appears that the balancer can pile up requests on mongrel because
> > there is no way to tell apache to not send more than one request at a
> > time to any single balance member.  I''m also not sure how
well things
> > are handled if a mongrel process hangs in some way.  Not that it would
> > of course:)
> >
> > Suggestions?
> >
> > Chris
>
>
> Chris-
>
>         Haproxy is a software proxy that can do the right thing and not
> overload mongrels. But it is not a webserver. I have used it behind
> nginx. So nginx or apache proxy to one haproxy and then haproxy does
> the load balancing in a more inteligent way then apapche ro nginx can
> do right now.
>
>         But Igor the author of nginx said that he will be adding a max-load
> to the ngixn proxy module which you could set to one and then ngxin
> would queue requests instead of mongrel and only send requests to
> mongrels that are not busy. This will be the best option with the
> least moving parts once he adds this feature.
>
> Cheers-
> -- Ezra Zygmuntowicz
> -- Lead Rails Evangelist
> -- ez at engineyard.com
> -- Engine Yard, Serious Rails Hosting
> -- (866) 518-YARD (9273)
>
>
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