Linux – How to run a stack trace on Apache

apache-2.2centoslinuxPHP

I have a PHP web application running on Apache/mod_php that works fine for several days and then fails, returns 500 Internal Server Error.

I've turned on debug logging and do not see anything in the logs that points to a cause. The only way to fix the issue is to restart Apache.

I think I need to run a system trace to monitor the Apache process and force it fail using Apache bench or other load test tool. Problem is, I've never done this before so I'm not sure how I would go about it.

I am running CentOS 6.x. What tool would I use to run a system trace and how would I invoke it?

Best Answer

You can try strace

strace -f -p 22254 -s 80 -o /tmp/debug.lighttpd.txt

-p will be the PID of the apache process, this thread helps you finding it

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Linux Bash – How to Sort du -h Output by Size

As of GNU coreutils 7.5 released in August 2009, sort allows a -h parameter, which allows numeric suffixes of the kind produced by du -h:

du -hs * | sort -h

If you are using a sort that does not support -h, you can install GNU Coreutils. E.g. on an older Mac OS X:

brew install coreutils
du -hs * | gsort -h

From sort manual:

-h, --human-numeric-sort compare human readable numbers (e.g., 2K 1G)

Apache/PHP – Determine Cause of Memory Leak

Tracking down WHAT is causing the problem can be a pain in the ass. The first thing I'd do if I had a problem like that is reduce MaxRequestsPerChild to an aggresively low number (~100-200) and see if that makes a difference. If it does, then you probably have code that is leaking memory in a loop somewhere and you'll want to run a code audit.

Another thing to look at is Apache's fullstatus, see if you can find out what particular request is causing the memory leak. Get the PIDs on your suspected processes and run an strace on them.

Best Answer

Related Solutions

Linux Bash – How to Sort du -h Output by Size

Apache/PHP – Determine Cause of Memory Leak

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