apache2 process hangs after some time

Question

We have a dedicated server, with the following configuration: AMD Athlon (tm) 64 X2 Dual Core Processor 5600 + Memory: 4GB OS: Debian 4.0, kernel: 2.6.18-5-amd64 Apache/2.2.3 PHP/5.2.0-8 MYSQL: 5.0.32

The server works without problems, when suddenly from unknown causes httpd process hangs and consumes 50% CPU power. The situation presents the following chart:

http://img26.imageshack.us/img26/1615/image001.png

We can not locate a cause or an effective remedy similar situations. Maybe some of you know how to locate the cause or how to deal with its consequences.

Answer 1

Try connecting to the processes with strace

strace -p $PID_OF_SPINNING_WORKER

This should produce a list of system calls that the worker is calling, possibly in a loop, looking for a file or other resource.

If this produces nothing, then the process may be spinning in a loop, you can use gdb to connect to the worker and find out the general area of execution

gdb -p $PID_OF_SPINNING_WORKER
(gdb) bt 

Answer 2

The first place to check is the system logs. Is anything odd showing up in:

/var/log/apache2/error.log
/var/log/apache2/access.log
/var/log/syslog

Note if you're using virtual hosting then the Apache 2 log files might be in a different location.

Answer 3

Is this server in a live environment? If not, by looking through the apache logs- especially the error logs, you should be able to work out what process is causing this. It would be worth asking apache to log the process ids into the logs, so that when this happens you can see what the process was doing.