[Mongrel] problems with apache 2.2 proxying to mongrel cluster

Michael Kovacs kovacs at gmail.com
Tue Jan 2 17:32:46 EST 2007

Hmm... thanks for the suggestion I'll give that a look as well as  
search the archives here.

I do have the logger rotating daily right now:
config.logger = Logger.new(config.log_path, 'daily')

I think I'll remove that and see if this occurs again. The thing that  
still bothers me though
is that if one mongrel is broken from this shouldn't they all be? I  
can always count on 1 of 4 mongrels
working so that every 3rd request is successful :-) In order to  
monitor that I'd have to hit the site twice to
ensure that I'm not just getting the good mongrel on the first hit.  
Not very fresh.


On Jan 2, 2007, at 1:36 PM, Joey Geiger wrote:

> This may have to do with log rotation. There was a thread about
> similar issue posted in I believe December. You might want to try
> searching the mailing list archives.
> You're probably rotating your logs based on a specific size, which is
> why it's happening every couple hours, instead of nightly.
> On 1/2/07, Michael Kovacs <kovacs at gmail.com> wrote:
>> Hi all,
>> I've been having problems with the apache 2.2-mod_proxy_balancer- 
>> mongrel
>> setup.
>> My setup is:
>> CentOS 4.3
>> apache 2.2.3 (compiled from source) with mod_proxy_balancer
>> mysql 4.1
>> ruby 1.8.4
>> mongrel 0.3.14 (I know I need to update but I think this problem is
>> independent of the mongrel version)
>> mongrel_cluster 0.2.0
>> rails_machine 0.1.1
>> I have apache setup as per Coda's configuration on his blog  
>> posting from
>> several months back.
>> http://blog.codahale.com/2006/06/19/time-for-a-grown-up-server- 
>> rails-mongrel-apache-capistrano-and-you/
>> I have 4 mongrels in my cluster.
>> Things work fine for periods of time but after several hours of  
>> inactivity
>> (I think 8 hours or so) I experience oddness where only 1 of the 4  
>> mongrels
>> is properly
>> responding. I end up getting a "500 internal server error" 3 out of 4
>> requests as they round robin from mongrel to mongrel. There is  
>> nothing in
>> the production
>> log file nor in the mongrel log. I've reproduced this problem on  
>> my staging
>> box as well as my production box.
>> The last time I reproduced the problem I decided to run "top" and  
>> see what's
>> going on when I hit the server.
>> Mongrel does receive every request but mysql is only active on the  
>> 1 request
>> that works. In the other mongrels it never spikes up in CPU usage.
>> Looking at the mysql process list revealed that all of the  
>> processes had
>> received the "sleep" command but one of the processes is still
>> working properly. I've played with connection timeouts other than  
>> to set the
>> timeout in my application's environment
>> (ActiveRecord::Base.verification_timeout = 14400) as well as the  
>> mysql
>> interactive_timeout variable but it seems that all the mongrels  
>> should work
>> or they shouldn't. The fact that 1 out of 4 always works is rather  
>> puzzling
>> to me.
>> Trying a 'killall -USR1 mongrel_rails" to turn debug on simply  
>> killed the 4
>> threads running mongrel. So now I'm running the cluster in debug  
>> mode and am
>> going to just let it sit there for several hours until it happens  
>> again and
>> hopefully get some idea of where the breakdown is happening. I  
>> still think
>> it has to be a mysql connection timeout but again, the fact that 1  
>> of the 4
>> always works doesn't lend credence to the timeout theory.
>> Has anyone experienced this phenomenon themselves?
>> Thanks for any tips/pointers and thanks Zed for all your hard work  
>> with
>> mongrel.
>> -Michaelhttp://javathehutt.blogspot.com
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