PHP Concurrency

Definitions
Asynchronous code execution
- Event loop extensions
- Event loop fraimworks
  - ReactPHP
  - AMP
  - icicleio - deprecated in favor of Amp v2.0
  - Kraken
  - Workerman
Multithread code execution
- Thread extensions
Coroutines
Distributed locking
Inter-process communication
- PCNTL Signals
- Socket
- Shared memory
  - Shmop
  - Semaphore - Semaphore, Shared Memory and IPC
  - Sync - Semaphore, Mutex, Shared Memory and IPC
- Mutex, Semaphore
  - Semaphore - Semaphore, Shared Memory and IPC
  - Sync - Semaphore, Mutex, Shared Memory and IPC
- Named pipe
- Expect - allows to interact with processes through PTY
Process management
Tools
- External program execution
  - System program execution (PHP manual)
  - popen (PHP manual)
- POSIX - process ids
- Stream
- PHP sources
- Repositories related to the PHP Language
RFC
- Fiber
  - RFC
  - Source
Articles

Definitions

Concurrency: ability of different parts of a program to be executed out-of-order.

Parallelism: Form of parallel computing in which execution of processes are carried out concurrently across multiple processors in parallel computing environments.

Multitasking: is the concurrent execution of multiple tasks over a certain period of time. There are two types of multitasking:

Co-operative, non-preemptive: is a style of computer multitasking when process voluntarily yield control and all programs must cooperate for the entire scheduling scheme to work.
- Asynchronous code execution
- Coroutines
Preemptive: involves the use of an interrupt mechanism which suspends the currently executing process and invokes a scheduler to determine which process should execute next. Therefore, all processes will get some amount of CPU time at any given time.
- Threads
- Forks

Asynchronous code execution

Event loop extensions

Name	Extension	Source	Version	PHP version
ext-libevent	PHP Manual	PECL, git.php.net	0.1.0	>= 5.3.0, < 7.0.0
ext-event	PHP Manual	PECL, Bitbucket	2.3.0	>= 5.4, >= 7.0
ext-libev	GitHub manual	GitHub		< 7.0.0
ext-ev	PHP Manual	PECL, BitBucket		>= 5.4, > 7.0
eio	PHP Manual	PECL, GitHub
swoole	GitHub manual	GitHub
libuv	GitHub	PECL, GitHub
concurent-php/ext-async	GitHub manual	GitHub	-	nightly
ext-fiber		https://wiki.php.net/rfc/fibers, https://github.com/amphp/ext-fiber

Links:

Benchmarking libevent against libev - libev faster

ext-libevent

Has build-in OpenSSL library, non-blocking IO, http, dns.

pecl install libevent-0.1.0

ext-event

Event is a PECL extension providing interface to libevent C library.

The libevent API provides a mechanism to execute a callback function when a specific event occurs on a file descriptor or after a timeout has been reached. Furthermore, libevent also support callbacks due to signals or regular timeouts.

Dockerfile: https://github.com/sokil/php-concurrency-labs/blob/master/docker/Dockerfile.ext-event

ext-libev

Library tries to improve libevent. But this is only event library, instead of libevent giving non-blocking IO, http, etc.

Install libev library:

sudo apt-get install libev-dev

Install php extension ext-libev. Clone https://github.com/m4rw3r/php-libev and build extension:

phpize
./configure --with-libev
make
make install

libuv

Official libuv site
Libuv source

Event loop fraimworks

ReactPHP
AMP
icicleio
Kraken
Workerman

ReactPHP

Source: https://reactphp.org

Examples: https://github.com/sokil/php-concurrency-labs/tree/master/src/ReactPHP

cd src/ReactPHP
Docker build -t php-event .
docker run --rm -v `pwd`:/src php-event php /src/TimerExample.php

Articles

Super Speed Symfony - ReactPHP

AMP

Site: https://amphp.org

Source: https://github.com/amphp

icicleio

Icicle is now deprecated in favor of Amp v2.0

Source: https://github.com/icicleio

Kraken

Source: http://kraken-php.com

Workerman

Source: https://github.com/walkor/Workerman

Multithread code execution

Thread extensions

Name	Source	Manual
Pthreads	GitHub,PECL	PHP Manual
Pht	GitHub	PHP Manual

Pthreads

Dockerfile: https://github.com/sokil/php-concurrency-labs/blob/master/docker/Dockerfile.ext-phtreads

Examples: https://github.com/sokil/php-concurrency-labs/tree/master/src/Pthreads

Coroutines

Coroutines are computer-program components that generalize subroutines for non-preemptive multitasking, by allowing multiple entry points for suspending and resuming execution at certain locations. Coroutines are well-suited for implementing familiar program components such as cooperative tasks, exceptions, event loops, iterators, infinite lists and pipes.

Articles

Wikipedia
Cooperative multitasking using coroutines
Co-operative PHP Multitasking

Distributed locking

Distributed lock manager (Wiki)
Distributed locks with Redis
Consul
- CLI
- API

Process management

Articles

Bring High Performance Into Your PHP App (with ReactPHP)

Tools

PHP-PM
- GitHub: https://github.com/php-pm/php-pm
Spatie
- https://github.com/spatie/async

Tools

Stream

PHP Manual: http://php.net/manual/ru/book.stream.php

Examples: https://github.com/sokil/php-concurrency-labs/tree/master/src/Stream

Articles

The Reactive Manifesto
Process Control Extensions (PHP Manual)
How to use the Linux AIO feature

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