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From Pid <...@pidster.com>
Subject Re: Tomcat 5.5/HTTPD cluster question
Date Fri, 31 Dec 2010 10:42:17 GMT
On 12/31/10 3:46 AM, Don Hill wrote:
> Chris,
> 
> Thanks for following up on this. From what I can tell it appears that the
> HTTPD server is stalling at MaxClients. 

How are you measuring connections and arriving at the above?
The documentation for 2.0 states that MaxClients is configurable:

 http://httpd.apache.org/docs/2.0/mod/mpm_common.html#maxclients


> This usually happens after some
> mailing and the site gets hit really hard with users, upward of 3000 active
> sessions being handle by 2 HTTPD servers and 4 Tomcat instances. 

What do you mean by 'sessions' and how are you counting them?
HttpSessions in Tomcat, or something else?


> Since we
> are using prefork/mod_jk it seems there could also be some high CPU usage.

Why prefork *or* mod_jk?

Could be, or is high CPU usage?  What is your average CPU usage per
machine?  And at peak load?

> I
> have done extensive profiling from a heap perspective using jstat and jmap.
> I think I have the JVM tuned pretty good at this point.

What are your JVM settings?


> The Tomcat severs
> also had maxthreads for each JVM set really high like 1000 on the AJP/1.3
> connector. I brought each JVM down to 200 max threads.

What do you have in the mod_jk config for each worker?


> Currently there are 2 VHOSTS on each machine with one  HTTPD instance. We
> are load balancing via a F5 Load balancer. The LB manages load accros all 4
> VHOST. Each VHOST uses one worker for to talk to one dedicated tomcat JVM.

How does the F5 distinguish between vhosts, are they named differently?

So there's 2 HTTPD with 2 vhosts and 4 Tomcats, is the below correct?

                            LB
                  ---------------------
                  |                    |
                HTTPD                HTTPD
             -----------          -----------
             |          |         |          |
          Tomcat     Tomcat    Tomcat     Tomcat


The Tomcat's have 200 threads each, so your max concurrent connections
is 800.  What led you to reduce the number of connections?


p

> Besides doing upgrades to Tomcat/HTTPD servers do you think there are any
> configuration issues or can you suggest a better layout for this env. I was
> thinking of getting rid of the vhosts and use a balancer config in the
> mod_jk.config to manage the load to the Tomcat JVMs. This way the load could
> be balanced based on the Tomcat usage and not the VHOST usage as some of the
> load could be coming from static content and messing up the LB's balancing
> ability.
> 
> I was also thinking that we should switch to worker mpm instead of the
> prefork.
> 
> Anyways any thoughts or suggestions would be great.
> 
> 
> 
> On Thu, Dec 30, 2010 at 8:19 PM, Christopher Schultz <
> chris@christopherschultz.net> wrote:
> 
> Don,
> 
> On 12/30/2010 10:41 AM, Don Hill wrote:
>>>> My mistake, Here are the details. I should have confirmed first before
>>>> posting but besides the apache version everything else is correct.
>>>>
>>>> tomcat 5.5.2.7
> 
> That's not a version published by Tomcat. More likely, this is a version
> packaged by RHEL. If it's really based upon Tomcat 5.5.2 (a reasonable
> guess), you seriously need to upgrade. If that was a typo and you are
> really running Tomcat 5.5.27, then you could still afford to upgrade to
> 5.5.31 which is the latest.
> 
> You described your environment to a certain extent, but didn't say what
> your goals were: are you experiencing any problems with your setup? Are
> you just looking to streamline things so that you can increase load
> without having to upgrade anything?
> 
> If things are going well, why change anything?
> 
> If you have a specific goal, let us know what it is and maybe we can
> help you with it.
> 
> -chris
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