How to end the Swoole process correctly

Swoole is an asynchronous and parallel PHP network programming framework, which can greatly improve the performance and concurrency capabilities of PHP applications. In the process of using Swoole to develop applications, we will inevitably encounter situations where we need to end the Swoole process. This article will introduce Swoole's process management and how to end Swoole correctly.

1. Swoole's process management

In Swoole, we can use the Swoole\Process class to create child processes. When a child process ends, the parent process needs to recycle the child process in time, otherwise a zombie process will appear, which will occupy system resources and be detrimental to program performance.

In Swoole, we can end the process in the following two ways:

1. Call the exit method

In Swoole, we can call the exit method to end the current process process. The following is a simple example:

$process = new Swoole\Process(function (Swoole\Process $process) {
    echo "Child process start" . PHP_EOL;
    sleep(10);
    echo "Child process end" . PHP_EOL;
    $process->exit(0); // 结束进程
});

$process->start();
swoole_process::wait(); // 回收子进程

After the child process has executed all business logic, the exit method is called to end the process, and the parent process calls the swoole_process::wait() method to recycle the child process.

2. Call the kill method

We can also end the specified process by calling the kill method. The following is an example:

$pid = $process->start();
Process::kill($pid, SIGTERM); // 结束进程

Here the PID of the specified process is passed Give the kill method to end the specified process.

2. How to correctly end Swoole

Correctly ending the Swoole process involves two issues:

1. How to listen for the end signal

In Swoole, the process will not handle any signals by default, so we need to register a signal listener for the process.

The following is an example of a Swoole process:

$server = new Swoole\Http\Server("127.0.0.1", 9501);

$server->on("start", function () {
    // 注册信号监听器
    $signalHandler = function ($signal) use ($server) {
        echo "Receive signal $signal" . PHP_EOL;

        // 等待所有Worker进程结束
        $server->shutdown();
    };

    Swoole\Process::signal(SIGTERM, $signalHandler);
    Swoole\Process::signal(SIGINT, $signalHandler);
});

$server->on("workerStart", function () {
    // 设置Work进程的异常处理函数
    set_exception_handler(function (Throwable $exception) {
        echo $exception->getMessage() . PHP_EOL;

        // 退出进程
        exit(1);
    });
});

$server->on("request", function ($request, $response) {
    $response->end("Hello Swoole\n");
});

$server->start();

In the above code, we registered listeners for the two signals SIGTERM and SIGINT for the process. When these two signals are received, The $server->shutdown() method will be executed to stop the Server process. In addition, in each Worker process, we also set up an exception handling function. When an exception occurs in the code of the Worker process, the exception information will be printed and the process will exit.

2. How to wait for the process to end

After we receive the end signal through the registered signal listener, we need to wait for all Worker processes to end before exiting the process, otherwise the Worker process may still in running condition.

In Swoole, we can wait for all Worker processes to end by calling the $serv->shutdown() or $serv->stop() method.

The difference between $serv->shutdown() and $serv->stop() is:

• The shutdown method directly ends all Worker processes in the main process, and The shutdown method will wait for all Worker processes to end before ending the Server process.
• The stop method will negotiate with the Worker process to end the process. Each Worker process will perform cleanup work (such as clearing timers, ending all events, etc.) to ensure that the exit process is clean and complete.

The following is an example of using the shutdown method to end the Swoole process:

$serv = new Swoole\WebSocket\Server("0.0.0.0", 9501);

$serv->on("Start", function () use ($serv) {
    // 注册信号监听器
    $signalHandler = function ($signal) use ($serv) {
        echo "Receive signal $signal" . PHP_EOL;

        // 停止Server
        $serv->shutdown();
    };

    Swoole\Process::signal(SIGTERM, $signalHandler);
    Swoole\Process::signal(SIGINT, $signalHandler);
});

$serv->on("workerStart", function () {
    // 设置Work进程的异常处理函数
    set_exception_handler(function (Throwable $exception) {
        echo $exception->getMessage() . PHP_EOL;

        // 退出进程
        exit(1);
    });
});

$serv->on("message", function ($serv, $frame) {
    $serv->push($frame->fd, "Hello Swoole");
});

$serv->start();

In the above example, we registered listeners for the two signals SIGTERM and SIGINT for the Server process, and Call the $serv->shutdown() method to end the process when receiving the end signal.

Summary

In Swoole, ending the process correctly is a very important topic. We need to register a signal listener for the Swoole process and wait for all Worker processes to end before ending the process to avoid zombie processes or Worker processes still running. At the same time, we also need to set up an exception handling function in each Worker process to ensure that the process exits in time when an exception occurs.

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