Locating memory leak in Apache httpd process, PHP/Doctrine-based application
- by Sam
I have a PHP application using these components:
Apache 2.2.3-31 on Centos 5.4
PHP 5.2.10
Xdebug 2.0.5 with Remote Debugging enabled
APC 3.0.19
Doctrine ORM for PHP 1.2.1 using Query Caching and Results Caching via APC
MySQL 5.0.77 using Query Caching
I've noticed that when I start up Apache, I eventually end up 10 child processes. As time goes on, each process will grow in memory until each one approaches 10% of available memory, which begins to slow the server to a crawl since together they grow to take up 100% of memory.
Here is a snapshot of my top output:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1471 apache 16 0 626m 201m 18m S 0.0 10.2 1:11.02 httpd
1470 apache 16 0 622m 198m 18m S 0.0 10.1 1:14.49 httpd
1469 apache 16 0 619m 197m 18m S 0.0 10.0 1:11.98 httpd
1462 apache 18 0 622m 197m 18m S 0.0 10.0 1:11.27 httpd
1460 apache 15 0 622m 195m 18m S 0.0 10.0 1:12.73 httpd
1459 apache 16 0 618m 191m 18m S 0.0 9.7 1:13.00 httpd
1461 apache 18 0 616m 190m 18m S 0.0 9.7 1:14.09 httpd
1468 apache 18 0 613m 190m 18m S 0.0 9.7 1:12.67 httpd
7919 apache 18 0 116m 75m 15m S 0.0 3.8 0:19.86 httpd
9486 apache 16 0 97.7m 56m 14m S 0.0 2.9 0:13.51 httpd
I have no long-running scripts (they all terminate eventually, the longest being maybe 2 minutes long), and I am working under the assumption that once each script terminates, the memory it uses gets deallocated. (Maybe someone can correct me on that).
My hunch is that it could be APC, since it stores data between requests, but at the same time, it seems weird that it would store data inside the httpd process.
How can I track down which part of my app is causing the memory leak?
What tools can I use to see how the memory usage is growing inside the httpd process and what is contributing to it?
