Re: Help troubleshooting performance issue, after "1000 total children" Apache no longer responds to HTTP requests. Not MaxClients issue?

[Anam Ali Khan <anamalikhan@xxxxxxxxx>]

PJ

You have increased "Max Open files" setting BUT i think you should increased "open files descriptor" limit at operating system level.

There is a linux kernel parameter "file-max" in /proc that does the trick. Try increasing to 10000000.

Hope this will help

Thanks!

Anam

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From: P J <pauljflists@xxxxxxxxx>
To: users@xxxxxxxxxxxxxxxx
Sent: Saturday, 5 May 2012, 0:20
Subject: Re: [users@httpd] Help troubleshooting performance issue, after "1000 total children" Apache no longer responds to HTTP requests. Not MaxClients issue?

On Fri, May 4, 2012 at 8:46 AM, Tom Evans <tevans.uk@xxxxxxxxxxxxxx> wrote:

On Fri, May 4, 2012 at 4:18 PM, P J <pauljflists@xxxxxxxxx> wrote:
> On Fri, May 4, 2012 at 5:28 AM, Jim Jagielski <jim@xxxxxxxxxx> wrote:
>>
>> The closer MinSpareServers/MaxSpareServers are, the more time
>> Apache needs to spend killing and creating child processes
>> to ensure it stays within that narrow limit
>> On May 3, 2012, at 2:40 PM, P J wrote:
>>
>
> Thanks. Yes, I understand that. I set them both to that number to try and
> induce the issue we've been seeing.
> If I set:
>
> MinSpareServers  1024
> MaxSpareServers  2048
>
> 1000+ simultaneous connections is not uncommon this server.
>

This is unlikely to have a major effect on your issue, as I believe
something strange is going on when you reach 1024 processes, but why
do you have MinSpareServers so high?

If you start 1024 children initially, and then 900 of them are busy,
you are asking httpd to ensure there are at least 1924 children. It
seems massive overkill to ensure that there are so many idle
processes.

If your high water mark is (say) 1536 clients, and you start 1024
processes, then I would go with settings like this:

MinSpareServers 128
MaxSpareServers 1536
StartServers 1024
MaxClients 2048
ServerLimit 2048

So, you start with 1024 processes, increasing up to a maximum of 2048
processes. If there are ever more than 1536 processes idle, kill some
off.

Cheers

Tom

 

Thanks Tom, I agree. I don't normally have MinSpareServers at 1024, I was just trying to see if I can force it to throw the:

"[debug] mpm_common.c(663): (70007)The timeout specified has expired: connect to listener on [::]:80 error". error.

Which I can. The million $ questions is what is the magic 1024 limit I'm hitting.

I'll hopefully try with a later version of Apache and let the list know if that resolves it.

Thanks again.

--

PJ