Multi-process programming and process management technology in PHP

1. Preface

As a popular programming language, PHP has been widely used in various fields. In the case of high concurrency, large data volume, and high load, PHP's single-threaded characteristics will cause performance bottlenecks. In order to make full use of all the CPU, memory and IO resources of the machine and improve the performance and scalability of the program, multi-process technology needs to be used.

2. What is multi-process programming?

In the operating system, a process refers to a program being executed. Multi-process programming refers to dividing a program into multiple processes for execution. Each process is independent of each other and can be executed concurrently, thereby improving the throughput and processing capabilities of the program.

In PHP, the pcntl extension library is usually used to implement multi-process programming.

3. How to use PCNTL extension library?

First, you need to enable the pcntl extension library in the php.ini file.

extension=pcntl.so

Use the pcntl_fork() function to create a new child process. The child process and the parent process share the code segment, data segment and stack segment, but each has an independent running space and process identity.

$pid = pcntl_fork();
if ($pid == -1) {

// fork失败

} else if ($pid) {

// 父进程

} else {

// 子进程

}

Use the pcntl_waitpid() function to wait for the child process to end and obtain the status code returned by the child process.

$status = null;
$pid = pcntl_waitpid($child_pid, $status, WNOHANG);
if ($pid == -1) {

// waitpid错误

} else if ($pid) {

// 子进程已结束，$status中是子进程的状态码

} else {

// 子进程还在运行

}

Use the pcntl_sigprocmask() function to mask/restore the signal received by the process.

pcntl_sigprocmask(SIG_BLOCK, [SIGTERM]);
// After receiving the SIGTERM signal, the process will not be terminated immediately, but will wait until the process is completed before exiting
pcntl_signal(SIGTERM, function() {

// 处理SIGTERM信号

});
pcntl_sigprocmask(SIG_UNBLOCK, [SIGTERM]);

4. Process management technology

In practical applications, it is necessary Manage processes, including starting, stopping, restarting, monitoring and other functions of processes. Commonly used process management technologies are as follows:

4.1 Supervisord

Supervisor is a process manager that can start, stop, restart, and monitor multiple processes. It has a client and a server. The client sends control commands to the server, and the server controls the running status of the process. Supervisor also supports process groups, logging, automatic restart if the program fails to start, custom scripts and other functions.

Supervisor's configuration file is very simple, using INI format and easy to maintain. The following is an example of a Supervisor configuration file:

[program:myprogram]
command=/usr/bin/php /path/to/myprogram.php
process_name=%(program_name)s_% (process_num)02d
numprocs=4
directory=/path/to/myprogram
autostart=true
autorestart=true
user=myuser
stdout_logfile=/var/log/myprogram .log
stderr_logfile=/var/log/myprogram.err

4.2 Systemd

Systemd is an initialization system used to replace sysvinit and upstart, and can also be used as a process manager. It can start, stop, restart, and monitor multiple processes, and supports functions such as process dependencies, automatic restart, process status query, and resource restrictions.

Systemd’s configuration file is more complex and uses the systemd.units file format. The following is an example of a Systemd configuration file:

[Unit]
Description=myprogram
After=network.target

[Service]
Type=simple
ExecStart=/usr/bin/php /path/to/myprogram.php
PIDFile=/run/myprogram.pid
Restart=on-failure
User=myuser

[Install]
WantedBy=multi-user.target

4.3 Docker

Docker is an open source application container engine that can quickly create, deploy, and run containers. In Docker, each container is an independent process, and the container can be managed using Docker's command line tools or API.

Docker provides an operating system-like environment, including file system, process space, network, etc., in which any application can be run. Docker also supports distributed deployment, container orchestration, image warehouse and other functions.

5. Summary

Multi-process programming and process management technology are widely used in network programming and system programming. Using multiple processes can improve the concurrent processing capabilities and throughput of the program. Using the process manager can more conveniently manage the starting, stopping, restarting, monitoring and other operations of the process. In practical applications, appropriate technologies need to be selected for development and deployment based on actual conditions.

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