Explore the operating mechanism of coroutines in Swoole

Swoole is a coroutine framework based on PHP, and its asynchronous IO performance is excellent. The core of Swoole is coroutine. Coroutine is a more lightweight concurrency mechanism than threads. It can switch tasks in the same thread to achieve concurrent execution. This article will explore the operating mechanism of coroutines in Swoole.

1. The concept of coroutines

Coroutines, also known as micro-threads, are a finer-grained concurrency mechanism than threads. The difference between coroutines and threads is that coroutines implement task switching through time slice rotation, while threads are switched by the operating system scheduler. Therefore, coroutines perform better than threads.

In Swoole, coroutine is a lightweight PHP thread. Coroutines can switch to execute different tasks in the same thread to achieve concurrent execution. Compared with the traditional thread pool mode, coroutines can avoid the overhead of thread context switching, and at the same time, coroutines have lower memory usage and higher execution efficiency.

2. Swoole’s coroutine implementation

Swoole implements coroutine scheduling and switching through the coroutine scheduler. The coroutine scheduler is a coroutine scheduling engine provided by Swoole. Coroutine execution tasks can be switched based on time slice rotation.

The implementation principle of the coroutine scheduler is as follows:

1. First, the scheduler will assign a state to each coroutine, such as waiting, executing, sleeping, etc.

2. The scheduler will manage the status of all coroutines through a task queue. When the execution of the current coroutine is completed, the scheduler will give priority to the coroutine in the waiting state for execution.

3. The coroutine will automatically determine whether the current task is completed during execution. If the current task is not completed, the coroutine will suspend it and then switch to other coroutines for execution until the next scheduling time before continuing to execute the suspended task.

4. During the execution of the coroutine, if an IO blocking operation occurs (such as network IO, file IO, database query, etc.), the coroutine will automatically suspend and set the current task status to sleep. When the IO blocking is completed, the coroutine will automatically wake up and set the task status to execution.

5. After the coroutine execution is completed, the scheduler will recycle resources and set the coroutine status to end.

3. Swoole’s coroutine advantages

Swoole’s coroutine has the following advantages:

1. Efficient: coroutines can switch task execution in the same thread, avoiding the need for The overhead of thread context switching also speeds up code execution.

2. Lightweight: The coroutine occupies very little memory resources and can support a large number of concurrent connections at the same time.

3. Easy to debug: Coroutines can provide more fine-grained debugging information to facilitate developers to debug.

4. Easy to maintain: Coroutine code is simpler and easier to maintain than traditional multi-threaded code.

4. Steps to use Swoole coroutine

1.Introduce Swoole’s coroutine library

Swoole’s coroutine library can be introduced directly through Composer, the command is as follows:

composer require swoole/Coroutine

2. Write coroutine code

In Swoole's coroutine, you can use the keyword yield to implement coroutine switching. The following is a simple example:

function test()
{

echo "coroutine starts", PHP_EOL;

$result = yield select(null, null, null, 0.5);

echo "coroutine ends, selected: ", $result, PHP_EOL;

}

// Start the coroutine
go(function () {

test();

});

3. Run Swoole coroutine service

Use the Server class provided by Swoole to create a coroutine service:

Coun(function () {

$server = new Server('0.0.0.0', 9501, SWOOLE_BASE);
$server->on('Connect', function ($server, $fd) {
    echo "Client $fd connected

";

});
$server->on('Receive', function ($server, $fd, $from_id, $data) {
    echo "Client $fd: $data

";

    $server->send($fd, "Server received 

");

});
$server->on('Close', function ($server, $fd) {
    echo "Client $fd closed

";

});
$server->start();

});

In Swoole's coroutine service, you can use the go keyword to create a coroutine, for example:

go(function () {

// 协程执行的任务

});

5. Summary

Swoole’s coroutine implementation is a very efficient and lightweight concurrency mechanism that can effectively solve PHP’s performance problems in high concurrency scenarios. . Through this article, we have learned about the operating mechanism and usage of coroutines in Swoole. I believe that readers will also have a deeper understanding of Swoole's coroutines.

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