Teach you to use the spatie/async library to write asynchronous PHP code

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For most programs written in PHP, its sole purpose is to execute a simple process composed of multiple tasks, among which Tasks must be performed sequentially, such as data processing. We always have to endure the stop and wait of synchronous programming. The synchronous style of code execution is called blocking, which means tasks will be executed one after the other. So what if we want to run tasks without them blocking each other, which means we need a non-blocking process? This approach requires the application of asynchronous programming methods in PHP, where tasks will be executed without interdependence.

A common way to achieve non-blocking execution in PHP is to implement queue processing. Tasks are persisted to a transport such as MySQL, Redis, Amazon SQS, etc., which is retrieved by a background worker and executed accordingly, thus not blocking the main process that created the task. Laravel applications provide a queuing mechanism that allows tasks (called jobs in this case) to be deferred to a later time for processing.

Another approach is to run all defined tasks in parallel. What we know from this approach is that as soon as a specific task is completed, it can hand control back to the main process with a promise to execute the code and notify us of the results later (e.g. callback). One may rarely see use cases for parallel processing methods; an example use case might be to perform image processing and make a GET request to some external service.

Let's look at the difference between synchronous and asynchronous (parallel) processes in PHP through a very simple use case.

Synchronous code

foreach (range(1, 5) as $i) {
    $output = $i * 2;
    echo $output . "\n";
}

Asynchronous code

use Spatie\Async\Pool;

$pool = Pool::create();

foreach (range(1, 5) as $i) {
    $pool[] = async(function () use ($i) {
       $output = $i * 2;
       return $output;
    })->then(function (int $output) {
       echo $output . "\n";
    });
}
await($pool);

When we execute the first code, we will do it in the following order Get the output value:

2
4
6
8
10

Retry the execution and we will get the same sequence of output as above. Therefore, each multiplication operation waits to be executed before the next multiplication operation. Next, run the second code block and let's see what we get.

6
10
2
8
4

Second retry execution:

2
6
4
10
8

A process produces two different results. This is exactly what we get using asynchronous methods. Our small tasks can be executed in a non-blocking manner. Each multiplication task is executed independently, some faster than others, so the output is jumbled. Also, note that our async function is attached as a then method, which is responsible for taking back control, and that it accepts a callback function as its argument, which can now perform additional actions on the received output.

The folks at Spatie have developed this nice spacee/async package which helps in executing tasks in parallel. You can install this package via Composer:

composer require spatie/async

This package provides a clever way to interact with created tasks that will be executed in parallel. The event listener of the task is described as follows:

• Execute the operation again when the task is completed because the callback can be implemented through its then method.
• When a specific task throws an exception using the catch method, error handling is easier to control.
• The timeout method allows one to handle scenarios when a task does not complete its operation.

The event listener is hooked up to the task as shown below:

$pool
    ->add(function () {
        // 要在并行进程中执行的任务
    })
    ->then(function ($output) {
        // 如果成功，进程或者你传递到队列的回调函数会返回`$output`。
    })
    ->catch(function ($exception) {
        // 当进程内抛出异常时，它会被捕获并传递到这里。
    })
    ->timeout(function () {
        // 哦，不！ 一个过程花了太长时间才完成。 让我们做点什么吧
    })
;

To learn more about this spacee/async package, please read its One of the contributors to this article, you can also refer to the GitHub repository.

Original address: https://dev.to/webong/using-asynchronous-processes-in-php-7io

Translation address: https://learnku.com/ php/t/51334

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