[Mongrel] Application 500 Errors

Zed A. Shaw zedshaw at zedshaw.com
Mon Oct 30 21:16:13 EST 2006

On Mon, 30 Oct 2006 15:46:14 -0500
"Jared Brown" <mongrelmail at gmail.com> wrote:

> Sure
> Mongrel
> Mongrel Cluster 0.2.0
> Ruby 1.8.4
> Rails 1.1.6
> Apache 2.2.2
> RHEL 4
> The symptom is that we are getting frequent application 500 errors.
> Monitoring the mongrel cluster shows some of the servers in Err status at
> any given moment. We run 40 mongrel instances in the cluster and only a few
> of them are in Err status at a time. Does a mongrel instance in Err status
> return an application 500 error? I have not found documentation on the
> cluster monitor.

Ok, this is much better.  I'm short on time but I'll do a more complete answer later.  First thing though, why so many Mongrels?  Try scaling it back to just 1, then slowly test the speed and ramp up the numbers of Mongrels until you hit a point where no more mongrels will give you more speed.

Next up, see if reduced mongrel numbers improves stability.  I've seen it where lots of processes will cause problems with Apache declaring something dead but it not really being dead.

And yes, when a mongrel goes bad it can return a 500, but apache is supposed to round robin to the next one in that case.  500 is usually only if all of them didn't answer.

Talk to you soon, and thanks for the improved info.

Zed A. Shaw, MUDCRAP-CE Master Black Belt Sifu
http://safari.oreilly.com/0321483502 -- The Mongrel Book
http://www.lingr.com/room/3yXhqKbfPy8 -- Come get help.

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