Introduction to message confirmation and retry mechanism in PHP message queue

Introduction to message confirmation and retry mechanism in PHP message queue

With the development of Internet applications, in the face of high concurrency and large traffic scenarios, the traditional direct request method can no longer meet the needs. As a decoupling and asynchronous processing technical solution, message queue is widely used in many enterprise-level applications. In PHP message queue, message confirmation and retry mechanism are two very important concepts. This article will introduce them in detail and give corresponding code examples.

1. Message confirmation mechanism

In the message queue, the message confirmation mechanism means that after the consumer receives the message, it sends a confirmation message to the message queue to inform the message queue that the message has been was successfully processed. If an exception occurs or processing fails when a consumer processes a message, the message queue will not receive confirmation information and will consider that the message processing failed and will redistribute the message to other consumers or retry the process.

The implementation of the message confirmation mechanism needs to consider the following two aspects:
(1) How the message consumer sends confirmation information to the message queue
(2) How the message queue handles the failure to receive confirmation information Message

In the PHP message queue, the AMQP (Advanced Message Queuing Protocol) protocol is usually used to implement the message confirmation mechanism. The following is an example of using rabbitmq:

<?php
$connection = new AMQPStreamConnection('localhost', 5672, 'guest', 'guest');
$channel = $connection->channel();

$channel->queue_declare('hello', false, false, false, false);

echo " [*] Waiting for messages. To exit press CTRL+C
";

$callback = function ($msg) {
    echo ' [x] Received ', $msg->body, "
";
    // 处理消息的业务逻辑

    // 发送确认信息给消息队列
    $msg->delivery_info['channel']->basic_ack($msg->delivery_info['delivery_tag']);
};

$channel->basic_consume('hello', '', false, false, false, false, $callback);

while (count($channel->callbacks)) {
    $channel->wait();
}

$channel->close();
$connection->close();

In the above code, a message queue connection and channel are created, and a queue named "hello" is declared. In the callback function, after performing business processing on the received message, call $msg->delivery_info['channel']->basic_ack($msg->delivery_info['delivery_tag']) to send confirmation information to the message queue.

For messages that have not received confirmation information, the message queue handles them according to specific strategies. A common processing method is to set the expiration time of the message. If the message does not receive confirmation information within a certain period of time, the message processing is considered to have failed, and the message queue will redistribute the message to other consumers.

2. Message retry mechanism

The message retry mechanism refers to the mechanism for retrying the message after the message processing fails. In the message queue, message retry can be based on the following two methods:
(1) Fixed number of retries: For messages that fail to be processed, the message queue will redistribute the message to the consumer and retry it each time. Increase the counter when retrying. When the counter reaches a fixed number of retries, the message queue will no longer retry, but will send the message to a specific failure queue to wait for manual intervention.
(2) Exponential-based retry time: For messages that fail to be processed, the message queue will redistribute the message to the consumer and determine the time interval for each retry based on the exponential method. Usually, the time interval between each retry is increased exponentially to avoid a large number of retries in a short period of time and reduce the system load.

The following is an example of using rabbitmq's message retry mechanism:

<?php
$connection = new AMQPStreamConnection('localhost', 5672, 'guest', 'guest');
$channel = $connection->channel();

$channel->queue_declare('task_queue', false, true, false, false);

echo " [*] Waiting for messages. To exit press CTRL+C
";

$callback = function ($msg) {
    echo ' [x] Received ', $msg->body, "
";
    // 模拟消息处理失败的情况
    if (rand(0, 10) < 3) {
        // 发送重试信息给消息队列
        $msg->delivery_info['channel']->basic_reject($msg->delivery_info['delivery_tag'], true);
    } else {
        // 处理消息的业务逻辑

        // 发送确认信息给消息队列
        $msg->delivery_info['channel']->basic_ack($msg->delivery_info['delivery_tag']);
    }
};

$channel->basic_qos(null, 1, null);
$channel->basic_consume('task_queue', '', false, false, false, false, $callback);

while (count($channel->callbacks)) {
    $channel->wait();
}

$channel->close();
$connection->close();

In the above code, a queue named "task_queue" is declared, using $channel- >basic_qos(null, 1, null);Set up to distribute only one message at a time, and simulate the message processing failure in the callback function. When processing fails, call $msg->delivery_info['channel']->basic_reject($msg->delivery_info['delivery_tag'], true); in the sample code to send a retry Try sending messages to the message queue.

Through the message confirmation mechanism and retry mechanism, PHP message queue can ensure the reliability of messages and the efficiency of processing. Developers can choose appropriate message confirmation and retry strategies based on actual needs to provide better user experience and system performance.

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