Swoole practical experience: using coroutines for high-concurrency email processing

With the rapid development of Internet technology and the continuous expansion of application scenarios, email services have become an indispensable part of the daily work of enterprises/individuals. However, in large-scale email sending, high concurrency often becomes a bottleneck, such as frequent connections or reconnections to the SMTP server, message queue consumption and other operations. These operations require a lot of time and system resources, affecting the entire email sending. process efficiency. So, how to achieve efficient email processing with minimal resources?

Practice has shown that using coroutines for high-concurrency email processing in Swoole is a very feasible and efficient method. This article will introduce some development practices on how to use Swoole's coroutine feature to achieve high concurrent email processing.

1. Introduction to coroutines

Coroutines are lightweight threads, which can be seen as a compromise between processes and threads. Coroutines have the following characteristics:

1. Low-cost context switching
2. No lock mechanism required
3. Lightweight resource occupation
4. Multi-tasking Collaboration

In Swoole's coroutine feature, coroutine operations can be performed through the following functions:

1. SwooleCoroutineun(callable $fn): Start a Swoole coroutine.
2. SwooleCoroutinecreate(callable $fn, bool $coroutine_params): Create a coroutine.
3. SwooleCoroutine::yield(): Pauses the execution of the current coroutine and does not release CPU resources.
4. SwooleCoroutine::resume($coroutine_id): Resume the specified coroutine.

2. Practice: Use Swoole’s coroutine feature to achieve high concurrent email processing

1. Initialize SMTP client

Use Swoole’s coroutine It is quite simple to handle email sending using the programming feature. We can send emails based on the PHPMailer library.

First you need to initialize the SMTP client and set the parameters related to the SMTP server:

try {
   $mail = new PHPMailer;
   $mail->isSMTP();
   $mail->SMTPDebug  = 0;
   $mail->SMTPAuth  = true;
   $mail->SMTPSecure = 'tls';
   $mail->Host   = "smtp.example.com";
   $mail->Port   = "465";
   $mail->CharSet = "utf-8";
   $mail->Username = "user@example.com";
   $mail->Password = "password";
   $mail->setFrom('user@example.com', 'Mailer');
   $mail->addAddress('recipient@example.com', 'Recipient');
   $mail->isHTML(true);
   $mail->Subject = 'Test email';
   $mail->Body    = 'This is the HTML message body <b>in bold!</b>';
   $mail->AltBody = 'This is the body in plain text for non-HTML mail clients';
}
catch (Exception $e) {
   echo "Message could not be sent. Mailer Error: {$mail->ErrorInfo}";
   exit;
}

2. Use coroutines to send high-concurrency emails

Next , we will use Swoole's coroutine feature to send multiple emails concurrently:

$tasks = array();
for ($i = 0; $i < $concurrency; $i++) {
   $tasks[] = SwooleCoroutine::create(function () use ($mail) {
       $result = $mail->send();
       if (!$result) {
           echo "Mailer Error: {$mail->ErrorInfo}
";
       } else {
           echo "Message sent successfully!
";
       }
   });
}
SwooleCoroutine::wait($tasks);

In this example, we use the SwooleCoroutine::create() function to create multiple coroutines. These coroutines will send multiple emails simultaneously. Finally, we use the SwooleCoroutine::wait() function to wait for all coroutines to complete execution.

3. Implementing SMTP server status maintenance

When the SMTP server receives a large number of connection requests, it may reject most of the requests in a short period of time. At this time we need to Complete the maintenance of SMTP server status during coroutine processing. For example, when the SMTP server rejects the request, we need to delay for a period of time before trying to send the email again. At this time we need to use the SwooleCoroutinesleep() function to achieve this.

For example, we can use the following code to maintain the status of the SMTP server:

$max_retry_count = 5;
for ($i = 0; $i < $concurrency; $i++) {
   $tasks[] = SwooleCoroutine::create(function () use ($mail, $max_retry_count) {
       $retry_count = 0;
       $result = false;
       while (!$result && $retry_count++ < $max_retry_count) {
           $result = $mail->send();
           if (!$result) {
               echo "Mailer Error: {$mail->ErrorInfo}
";
               if ($retry_count < $max_retry_count) {
                   $sleep_time = 2 ** ($retry_count - 1);
                   echo "sleep $sleep_time seconds before retrying...
";
                   SwooleCoroutine::sleep($sleep_time);
               }
           } else {
               echo "Message sent successfully!
";
           }
       }
   });
}

In this example code, we will retry sending emails and sleep for a period of time each time it fails. . Each sleep time will increase as the number of failures increases.

Summary

Swoole's coroutine feature provides a more convenient, fast and efficient way for high-concurrency email processing. In practice, it only takes a few lines of code to achieve high concurrent email processing by using Swoole's coroutine feature. If you want to develop other high-concurrency applications, you can also consider using Swoole's coroutine feature and try to integrate it into your project to improve application performance.

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