RabbitMq初探——消息均发

消息均发

前言

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由前文 RabbitMq初探——消息分发 可知，rabbitmq自带分发机制——消息会按顺序的投放到该队列下的多个消费者，例如1,3,5投放消费者C1，2,4,6投放消费者C2。

这就有个隐含的缺点：每个消息的消费时间可能不一样，极端情况下，投放给C1的每个消息消费都需要很长时间，而投放给C2的每个消息消费需要很短，就会导致C1进程

负担重,C2进程很悠闲。

所以，我们需要根据任务量来均发消息。

均发消息实现

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1. 开启消息确认机制。

2. 为每个消费者分配且只分配一个消息，待rabbitmq收到消费者的ack后再发送后面的消息。通过这种手段，耗时很短的消息消费掉，发送ack，rabbitmq收到确认，分配下一个

消息给该消费者。不会存在很悠闲的消费者进程。

php代码实现

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需要在消费者代码中加入 预定消息数量=1 的代码

$channel->basic_qos(null, 1, null);

整体代码如下：

sender.php

<?php
/**
 * sender.php
 * Created by PhpStorm.
 * User: wangdaxi
 * Date: 2017/10/18
 * Time: 14:26
 */
require_once __DIR__ . '/vendor/autoload.php';
use PhpAmqpLib\Connection\AMQPStreamConnection;
use PhpAmqpLib\Message\AMQPMessage;

$connection = new AMQPStreamConnection('127.0.0.1', 5672, 'guest', 'guest');
$channel = $connection->channel();

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

$data = implode(" ", array_slice($argv, 1));
empty($data) && $data = "Hello World!";

$msg = new AMQPMessage($data, array('delivery_mode' => AMQPMessage::DELIVERY_MODE_PERSISTENT));

$channel->basic_publish($msg, '', 'durable_queue');

echo " [x] Sent '$data'\n";

//close the channel and connection;
$channel->close();
$connection->close();

receive.php

<?php
/**
 * receive.php
 * Created by PhpStorm.
 * User: wangdaxi
 * Date: 2017/10/18
 * Time: 14:34
 */
require_once __DIR__ . '/vendor/autoload.php';
use PhpAmqpLib\Connection\AMQPStreamConnection;

$connection = new AMQPStreamConnection('127.0.0.1', 5672, 'guest', 'guest');
$channel = $connection->channel();

$channel->queue_declare('durable_queue', false, true, false, false);
$channel->basic_qos(null, 1, null);
echo ' [*] Waiting for messages. To exit press CTRL+C', "\n";

$callback = function($msg) {
    echo "[x] Received ", $msg->body, "\n";
    sleep(substr_count($msg->body, '.'));
    echo "[x] Done\n";
    //消息确认
    $msg->delivery_info['channel']->basic_ack($msg->delivery_info['delivery_tag']);
};
$channel->basic_consume('durable_queue', '', false, false, false, false, $callback);

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

验证

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开启两个终端作为消费者C1，C2。

开启一个终端作为生产者P。

P持续生产任务量不一样的消息（用.的个数表示任务量大小）

看C1处理消息

看C2处理消息

以上。