Re: Help me in setting up MaxClients

[Vikrama Sanjeeva <viki.sanjeeva@xxxxxxxxx>]

Hi All,

   Thanks Jeff for the presentation. Its informative.

Actually, I am trying to calculate what MaxClient I can set. I know my server is strong and as Danny and you said, setting 600 will not be a risk. I however, will prefer to do some calculation to drive this value. Since I am not Solaris command expert, therefore I am having difficulty in doing calculation.

My objective is to follow below formula to calculate MaxClient as mentioned on Apache site:
http://httpd.apache.org/docs/2.2/misc/perf-tuning.html

"This procedure
    for doing this is simple: determine the size of your average Apache
    process, by looking at your process list via a tool such as
    top, and divide this into your total available memory,
    leaving some room for other processes."

As I understand, it says:      (RAM Size / Avg HTTPD Process Size) - some room for other proceeses

Out of these 3 variables, I am able to conclude: 
RAM Size = 32544 MB
Avg httpd process size: 12 MB

But how to calculcate "size for other processes" ? One thing I want to highlight here is that; we are running application server (JBOSS) on same machine with almost 10 JVM nodes. Average Java process size for these are 3-4 GB. No other applications are running on this machine. And yes, we are using "mod_jk" for backend server loadbalancing.

Bye,
Viki. 


On Mon, Jan 25, 2010 at 5:44 PM, Jeff Trawick <trawick@xxxxxxxxx> wrote:

On Mon, Jan 25, 2010 at 8:56 AM, Vikrama Sanjeeva
<viki.sanjeeva@xxxxxxxxx> wrote:

> Hello All,
>
> This is regarding production servers. Recently Apache server hit MaxClient
> settings; resulting in crash of sites. However, sites was back to normal
> after restarting Apache.

The expected symptom is that Apache is unresponsive to additional
requests until some of the child processes finish what they're working
on.

Restarting Apache without increasing MaxClients isn't helpful; if it
is a hard restart it trashes the current connections.

> I read about MaxClient settings and increase it from 200 to 250 (as I read
> somewhere that 256 is a limit).

Run apachectl -V to see the limit; it should be in the tens of thousands.

>                                     Since then sites are working fine. But still
> I see average concurrent request on Apache is 180-200 which sometime goes to
> 220 as well. This is threatening, as we are planning to put more sites live
> on same Apache.
>
> Therefore, I am considering to increase MaxClient in order to handle
> "at-least" 600 concurrent request.
>
> I will be grateful if somebody can assist me in setting the right values for
> ServerLimit, MaxClient, MinSpareServers and MaxSpareServers.

(I'm trying to get a public URL for the slides I sent you privately
which offer some advice here.)

>                                                              Also, what
> maximum values I can have for MaxClients (want to know max concurrent users
> Apache can handle.)

That's workload-specific.  Here are some interesting notes from
someone playing with a similar box a few years ago:

http://www.stdlib.net/~colmmacc/2006/03/23/niagara-vs-ftpheanetie-showdown/

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