调试 LAMP/CakePHP 站点内存泄漏？

Question

I run a site on AWS, built on CakePHP 2.2.3, PHP 5.6.32, and a MySQL database. Recently, I've had problems with server crashes that seem to start when the server runs out of memory.

I've set up CloudWatch to monitor memory usage, and see the following over the last few days (server was reset ~5 days ago):

Running 'top' on the server produces the same result for memory usage.

This looks like a memory leak to me (is that correct?), but my understanding is that PHP 5.6 is supposed to do garbage collection. I don't use explicit memory allocation in my code at all, but can't rule out the possibility that CakePHP does. And maybe it's no a problem with PHP at all.

I'm new to web development, and am at a bit of a loss on where to start. Google searches come back with solutions to OOM errors due to large allocations, but that's not the issue here. What could cause a site to show an almost monotonically increasing memory usage like this? How should I go about finding the culprit?

Edit : Output of 'top' sorted by memory usage below, in case it's helpful.

Edit 2 : Output of 'atop -m' below.

Answer 1

My advice would be to connect to a profiling service https://blackfire.io or https://newrelic.com . They have in-depth profiling and logging and can be pretty precise when it comes to resource allocation and which script/module is the culprit.

Short of that, if you have some idea where in your application could be having an issue, you can use strace ( https://linux.die.net/man/1/strace ) to attach to your PHP process(es) to view the stack output and execute those scripts/modules.... strace is very handy when debugging a php process.

Good luck!

Answer 2

I went into the Mysql.php code of Cakephp, and set every variable to null after a closeCursor, like:

$cols->closeCursor(); $cols = null;

This stopped our memory leak and our crashes. It was normally topping at max memory and crashed after a while.