PHP RFC: Asynchronous Signal Handling (without TICKs)

• Version: 0.9
• Date: 2016-06-24
• Author: Dmitry Stogov, dmitry@zend.com
• Status: Under Discussion
• First Published at: https://wiki.php.net/rfc/async_signals

Currently php may handle OS signals using pcntl extensions:

• synchronously, calling pcntl_signal_dispatch() manually
• asynchronously, compiling scripts with declare(ticks=1)

However, TICKs introduce huge overhead.

Zend Engine in PHP 7.1 was extended with ability of safe time-out and interrupt handling. Actually, PHP VM checks for EG(vm_interrupt) flag on each loop iteration, user function entry or internal function exit, and call callback function if necessary.

I propose to use this ability to implement asynchronous signal handling. Registered signal handlers are going to be called at some points during user script execution without any overhead.

To keep ability of synchronous signal, handling we had to introduce a new INI directive pcntl.async_signals with default value 0. Bob pointed, that instead of INI directive, we may use function pcntl_async_signals(bool on_off). In my opinion, this doesn't make a big difference. In first case, some PHP script may don't know the value set through php.ini. In the second, it may don't know the previous value set through pcntl_async_signals().

None

PHP 7.1

• pcntl.async_signals=0

The vote is a straight Yes/No vote, that requires a 2/3 majority. The vote will begin on July 8 and finish on July 15.

An additional 1/2 majority question: Use pcntl.async_signals INI directive or pcntl_async_signals() function.

The patch is really simple: PR 1953

After the project is implemented, this section should contain

1. the version(s) it was merged to
2. a link to the git commit(s)
3. a link to the PHP manual entry for the feature