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

On Tue, May 1, 2012 at 7:22 AM, P J <pauljflists@xxxxxxxxx> wrote:

On Mon, Apr 30, 2012 at 10:37 AM, P J <pauljflists@xxxxxxxxx> wrote:

On Mon, Apr 30, 2012 at 9:13 AM, Alexandr Normuradov <normalex@xxxxxxxxx> wrote:

cat /proc/$(pidof -s httpd)/limitsTo troubleshoot that you should have
at least two additional outputs from

netstat -pant, with connections states
and
service httpd fullstatus, listing current state of all the apache procs/threads.

What applications your Apache is serving?
PHP? is it mod_php, mod_python, mod_perl?

What the vhost access log file for the most accessed vhost is showing?
Any pattern of slow, connections consuming attack?
If it is, and all tasks are in the Keep Alive wait then disable Keep
Alive and lower the general timeout to just 7 seconds.

The error "connect to listener on [::]:80" error is quite unusual.

ETIMEDOUT
Timeout while attempting connection. The server may be too busy to
accept new connections. Note that for IP sockets the timeout may be
very long when syncookies are enabled on the server.

cat /proc/sys/fs/file-nr

cat /proc/$(pidof -s httpd)/limits

Sincerely,
Alexandr Normalex

Hi Alexandr, thanks for taking a look at this with me.

The traffic pattern for this website is at certain times of the day it receives huge spikes of traffic in very short periods of time, trying to tune Apache to accommodate it the best we can.

cat /proc/$(pidof -s httpd)/limits

Limit Soft Limit Hard Limit Units
Max cpu time unlimited unlimited seconds
Max file size unlimited unlimited bytes

Max data size unlimited unlimited bytes
Max stack size 10485760 unlimited bytes
Max core file size 0 unlimited bytes

Max resident set unlimited unlimited bytes
Max processes 55296 55296 processes
Max open files 1024 1024 files

Max locked memory 32768 32768 bytes
Max address space unlimited unlimited bytes
Max file locks unlimited unlimited locks

Max pending signals 55296 55296 signals
Max msgqueue size 819200 819200 bytes
Max nice priority 0 0

Max realtime priority 0 0

cat /proc/sys/fs/file-nr
1530 0 560543

Looking at Max open files I see what is likely the problem :)

Max open files 1024

I swear I modified this to 4096! I've changed the limit to 4096 now, I'll double check it tomorrow. Hopefully this will be the obvious fix!

I will check service httpd fullstatus and netstat -pant tomorrow morning when this happens again, it happens the same time every day - it is not an attack, the customers application receives massive amounts of connections at certain times of the day.

I've been working with Apache for 15 years and I've never seen "connect to listener on [::]:80" error message before, I hope it's related to reaching Max open files.

Thanks again for your help.

--
PJ

I was hoping this would be fixed now that Max Open files has been updated, same issue this morning.

cat /proc/$(pidof -s httpd)/limits

Limit Soft Limit Hard Limit Units

Max cpu time unlimited unlimited seconds
Max file size unlimited unlimited bytes
Max data size unlimited unlimited bytes

Max stack size 10485760 unlimited bytes
Max core file size 0 unlimited bytes
Max resident set unlimited unlimited bytes

Max processes 55296 55296 processes
Max open files 1024 1024 files
Max locked memory 32768 32768 bytes

Max address space unlimited unlimited bytes
Max file locks unlimited unlimited locks
Max pending signals 55296 55296 signals

Max msgqueue size 819200 819200 bytes
Max nice priority 0 0
Max realtime priority 0 0

Once it reaches 1000 total children

[info] server seems busy, (you may need to increase StartServers, or Min/MaxSpareServers), spawning 32 children, there are 17 idle, and 1002 total children

After 1000 total children

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

Until apache is restarted.

I tried to run service httpd fullstatus during this time but it want able to connect:

ELinks: Connection refused.

I did capture the output of netstat -pant which shows many connections to the MySQL DB as well.
I've double checked MySQL has not reached max connections and that it's still working during this time.

netstat output is so big I have to put it up on pastebin:
http://pastebin.com/0DjvDnJp

I dont understand why this is happening at 1000 children, what limit is it hitting?

Apache config:

Timeout 30

KeepAlive On

MaxKeepAliveRequests 10000
KeepAliveTimeout 3

<IfModule prefork.c>
StartServers 80
MinSpareServers 50
MaxSpareServers 120

ServerLimit 3500
MaxClients 3500
MaxRequestsPerChild 4000
</IfModule

Any help would be greatly appreciated.

--
PJ

Haha, Max open files still says 1024!! I hardcoded it to 16384 yesterday, something keeps resetting it!

Let me figure this out before I keep bugging the list :)

Thanks,

--
PJ