Ordered messages, also known as first-in-first-out (FIFO) messages, are a type of messages provided by Message Queue for Apache RocketMQ. Such messages are published and consumed in a strict order. This topic provides the sample code about how to send and subscribe to ordered messages by using the HTTP client SDK for PHP.

Background information

Ordered messages are classified into the following types:
  • Globally ordered messages: All messages of a specified topic are published and consumed in first-in-first-out (FIFO) order.
  • Partitionally ordered messages: All messages of a specified topic are distributed to different partitions by using partition keys. The messages in each partition are published and consumed in FIFO order. A partition key is a key field that is used for ordered messages to distinguish among different partitions. It is different from the key of a normal message.

For more information, see Ordered message 2.0.

Prerequisites

Before you begin, make sure that the following operations are complete:

  • SDK for PHP is installed. For more information, see Prepare the environment.
  • Resources are created. The resources that you want to specify in the code are created in advance. For example, the instance, topic, and group ID that you want to specify in the code are created in the Message Queue for Apache RocketMQ console in advance. For more information, see Create resources.

Send ordered messages

The following sample code provides an example on how to send ordered messages:

<?php

require "vendor/autoload.php";

use MQ\Model\TopicMessage;
use MQ\MQClient;

class ProducerTest
{
    private $client;
    private $producer;

    public function __construct()
    {
        $this->client = new MQClient(
            // The HTTP endpoint. To obtain the HTTP endpoint, log on to the Message Queue for Apache RocketMQ console. In the left-side navigation pane, click Instances. On the Instances page, click the name of your instance. The endpoint is displayed on the Endpoints tab of the Instance Details page. 
            "${HTTP_ENDPOINT}",
            // The AccessKey ID that you created in the RAM console for identity authentication. 
            "${ACCESS_KEY}",
            // The AccessKey secret that you created in the RAM console for identity authentication. 
            "${SECRET_KEY}"
        );

        // The topic of the message. The topic is created in the Message Queue for Apache RocketMQ console. 
        $topic = "${TOPIC}";
        // The ID of the instance to which the topic belongs. The instance is created in the Message Queue for Apache RocketMQ console. 
        // If the instance has a namespace, you need to specify an ID for it. If the instance does not have a namespace, set the instance ID to null or an empty string. You can check whether your instance has a namespace on the Instance Details page in the Message Queue for Apache RocketMQ console. 
        $instanceId = "${INSTANCE_ID}";

        $this->producer = $this->client->getProducer($instanceId, $topic);
    }

    public function run()
    {
        try
        {
            for ($i=1; $i<=4; $i++)
            {
                $publishMessage = new TopicMessage(
                    "hello mq!"// The content of the message. 
                );
                // The custom attributes of the message. 
                $publishMessage->putProperty("a", $i);
                // The Sharding Key that is used to distribute ordered messages to a specific partition. The key field distinguishes a partition from other partitions. A Sharding Key is different from a message key. 
                $publishMessage->setShardingKey($i % 2);

                $result = $this->producer->publishMessage($publishMessage);

                print "Send mq message success. msgId is:" . $result->getMessageId() . ", bodyMD5 is:" . $result->getMessageBodyMD5() . "\n";
            }
        } catch (\Exception $e) {
            print_r($e->getMessage() . "\n");
        }
    }
}


$instance = new ProducerTest();
$instance->run();

?>

            

Subscribe to ordered messages

The following sample code provides an example on how to subscribe to ordered messages:

<?php

require "vendor/autoload.php";

use MQ\Model\TopicMessage;
use MQ\MQClient;

class ConsumerTest
{
    private $client;
    private $consumer;

    public function __construct()
    {
        $this->client = new MQClient(
            // The HTTP endpoint. To obtain the HTTP endpoint, log on to the Message Queue for Apache RocketMQ console. In the left-side navigation pane, click Instances. On the Instances page, click the name of your instance. The endpoint is displayed on the Endpoints tab of the Instance Details page. 
            "${HTTP_ENDPOINT}",
            // The AccessKey ID that you created in the RAM console for identity authentication. 
            "${ACCESS_KEY}",
            // The AccessKey secret that you created in the RAM console for identity authentication. 
            "${SECRET_KEY}"
        );

        // The topic of the message. The topic is created in the Message Queue for Apache RocketMQ console. 
        $topic = "${TOPIC}";
        // The group ID that you created in the Message Queue for Apache RocketMQ console. 
        $groupId = "${GROUP_ID}";
        // The ID of the instance to which the topic belongs. The instance is created in the Message Queue for Apache RocketMQ console. 
        // If the instance has a namespace, you need to specify an ID for it. If the instance does not have a namespace, set the instance ID to null or an empty string. You can check whether your instance has a namespace on the Instance Details page in the Message Queue for Apache RocketMQ console. 
        $instanceId = "${INSTANCE_ID}";

        $this->consumer = $this->client->getConsumer($instanceId, $topic, $groupId);
    }

    public function run()
    {
        // Cyclically consume messages in the current thread. We recommend that you use multiple threads to concurrently consume messages. 
        while (True) {
            try {
                // Consume messages in long polling mode. The consumer may pull partitionally ordered messages from multiple partitions. The consumer consumes messages from the same partition in the order that the messages are sent. 
                // Assume that a consumer pulls partitionally ordered messages from a partition. If the broker does not receive the acknowledgment (ACK) that a message is consumed, the consumer will consume the message again. 
                // The consumer can consume the next batch of messages from a partition only after all the messages pulled from the partition in the previous batch are acknowledged as consumed. 
                // In long polling mode, if no message is available for consumption in the topic, the request is suspended on the broker for a specified period of time. If a message is available for consumption during the period, the broker immediately sends a response to the consumer. In this example, the period is set to 3 seconds. 
                $messages = $this->consumer->consumeMessageOrderly(
                    3, // The maximum number of messages that can be consumed at a time. In this example, the value is set to 3. The maximum value of this parameter is 16. 
                    3  // The length of a long polling period. Unit: seconds. In this example, the value is set to 3. The maximum value of this parameter is 30. 
                );
            } catch (\Exception $e) {
                if ($e instanceof MQ\Exception\MessageNotExistException) {
                    // If no message is available for consumption in the topic, the long polling mode continues to take effect. 
                    printf("No message, contine long polling!RequestId:%s\n", $e->getRequestId());
                    continue;
                }

                print_r($e->getMessage() . "\n");

                sleep(3);
                continue;
            }

            print "======>consume finish, messages:\n";

            // Specify the service logic of processing messages. 
            $receiptHandles = array();
            foreach ($messages as $message) {
                $receiptHandles[] = $message->getReceiptHandle();
                printf("MessageID:%s TAG:%s BODY:%s \nPublishTime:%d, FirstConsumeTime:%d, \nConsumedTimes:%d, NextConsumeTime:%d,ShardingKey:%s\n",
                    $message->getMessageId(), $message->getMessageTag(), $message->getMessageBody(),
                    $message->getPublishTime(), $message->getFirstConsumeTime(), $message->getConsumedTimes(), $message->getNextConsumeTime(),
                    $message->getShardingKey());
                print_r($message->getProperties());
            }

            // If the broker does not receive a consumption ACK for a message from the consumer before the period of time specified in $message->getNextConsumeTime() elapses, the message will be consumed again. 
            // A unique timestamp is specified for the handle of a message each time the message is consumed. 
            print_r($receiptHandles);
            try {
                $this->consumer->ackMessage($receiptHandles);
            } catch (\Exception $e) {
                if ($e instanceof MQ\Exception\AckMessageException) {
                    // The broker may fail to receive a consumption ACK for a message from the consumer if the handle of the message times out. 
                    printf("Ack Error, RequestId:%s\n", $e->getRequestId());
                    foreach ($e->getAckMessageErrorItems() as $errorItem) {
                        printf("\tReceiptHandle:%s, ErrorCode:%s, ErrorMsg:%s\n", $errorItem->getReceiptHandle(), $errorItem->getErrorCode(), $errorItem->getErrorCode());
                    }
                }
            }
            print "=======>ack finish\n";


        }

    }
}


$instance = new ConsumerTest();
$instance->run();

?>