MemTrigger

A PHP extension to trigger events based on memory usage.

Example

$logAndGC = function () {
	echo "** Memory warning limit exceeded exceeded, calling GC when mem usage at ".number_format(memory_get_usage(false))."\n";
	gc_collect_cycles();
	echo "** Mem used now : ".number_format(memory_get_usage(false))."\n";
};

$MB = 1024 * 1024;
$logAndGCTrigger = new Trigger($logAndGC, 8 * $MB, Trigger::ACTION_LEAVE_ACTIVE);

trigger_init(5);
trigger_register($logAndGCTrigger);

The class methods and constants are documented in ./stubs.php

How to compile

phpize ./configure make install

By default the implementation hooks into the memory allocations for PHP 7. For PHP 5.6 it hook into the opcode execution.

To specify that the tracking

How it works and limitations

-dtrigger.mode=mem

php -dextension=./modules/trigger.so -dtrigger.mode=opcode ./test.php

Memory allocation hook

Opcode hook

In this mode, the extension replaces zend_execute_ex with a new function that both monitors the memory usage and calls the triggers when necessary, as well as calling the previous zend_execute_ex function.

Because of this it is not possible for all out of memory problems to be avoided. If either a single massive allocation uses more than the available remaining memory, or several very large allocations take quickly, this extension will not have a chance to detect and call a trigger about the large memory use.

TODO

• Currently there is not enough control over how frequently the triggers are called.

• Check that it actually works on real code.

• Allow triggers be checked at different rates.