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TDMQ for RocketMQ
DocumentationTDMQ for RocketMQRocketMQ 4.xPractical TutorialAccess over HTTPSDK for JavaSending and Receiving General Messages
Sending and Receiving General Messages
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Last updated: 2023-09-13 11:36:59
Sending and Receiving General Messages
Last updated: 2023-09-13 11:36:59
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Overview

TDMQ for RocketMQ can be accessed over the HTTP protocol from the private or public network. It is compatible with HTTP SDKs for multiple programming languages in the community.
This document describes how to use HTTP SDK to send and receive messages by using the SDK for Java as an example and helps you better understand the message sending and receiving processes.
Note
Currently, transactional message cannot be implemented over HTTP.
As a consumer group does not support simultaneous consumption by TCP and HTTP clients, you need to specify the type (TCP or HTTP) when creating a consumer group. For more information, see Group Management.

Prerequisites

You have created the required resources as instructed in Resource Creation and Preparation.
You have installed JDK 1.8 or later.
You have installed Maven 2.5 or later.
You have imported dependencies through Maven and added SDK dependencies of the corresponding programming language in the pom.xml file.
For more examples, see the demos in the open-source community.

Retry Mechanism

A fixed retry interval is used in HTTP, which can't be customized currently.
Message Type
Retry Interval
Maximum Number of Retries
General Message
5 minutes
288
Sequential message
1 minute
288
Note
If the client acknowledges a message within the retry interval, the message consumption is successful and will not be retried.
If the client doesn’t acknowledge a message after the retry interval has expired, the message will become visible again, and the client will consume it again.
The message handle consumed each time is only valid within the retry interval, and become invalid after that time period.

Directions

Step 1. Install the Java dependent library

Introduce dependencies in a Java project and add the following dependencies to the pom.xml file. This document uses a Maven project as an example.
<!-- in your <dependencies> block -->
  <dependency>
      <groupId>com.aliyun.mq</groupId>
      <artifactId>mq-http-sdk</artifactId>
      <version>1.0.3</version>
  </dependency>

Step 2. Get parameters

1. Log in to the TDMQ console, select the target cluster, and click the cluster name to enter the cluster details page.
2. Select the Namespace tab at the top and click Configure Permission on the right to enter the permission configuration page. If the role list is empty, click Create to create a role. For more information, see Resource Creation and Preparation.

3. Copy the AK and SK on the page for use in next steps.


Step 3. Produce messages

Creating a message producer

   // Get the client
   MQClient mqClient = new MQClient(endpoint, accessKey, secretKey);

   // Get the topic producer  
   MQProducer producer = mqClient.getProducer(namespace, topicName);
Parameter
Description
topicName
Topic name, which can be copied under the Topic tab on the Cluster page in the console.
namespace
Namespace name, which can be copied under the Namespace tab on the Cluster page in the console.

endpoint
Cluster access address over HTTP, which can be obtained from Access Address in the Operation column on the Cluster page in the console.
secretKey
Role name, which can be copied on the Role Management page.
accessKey
Role token, which can be copied in the Token column on the Role Management page.


Sending a message

try {
    for (int i = 0; i < 10; i++) {
        TopicMessage pubMsg;
        pubMsg = new TopicMessage(
            ("Hello RocketMQ " + i).getBytes(),
            "TAG"
        );
        TopicMessage pubResultMsg = producer.publishMessage(pubMsg);
        System.out.println("Send mq message success. MsgId is: " + pubResultMsg.getMessageId());
    }
} catch (Throwable e) {
    System.out.println("Send mq message failed.");
    e.printStackTrace();
}
Parameter
Description
TAG
Set the message tag.

Step 4. Consume messages

Creating a consumer

   // Get the client
   MQClient mqClient = new MQClient(endpoint, accessKey, secretKey);

   // Get the topic consumer  
   MQConsumer consumer = mqClient.getConsumer(namespace, topicName, groupName, "TAG");
Parameter
Description
topicName
Topic name, which can be copied under the Topic tab on the Cluster page in the console.
groupName
Producer group name, which can be copied under the Group tab on the Cluster page in the console.
namespace
Namespace name, which can be copied under the Namespace tab on the Cluster page in the console.

TAG
Subscribed tag.
endpoint
Cluster access address over HTTP, which can be obtained from Access Address in the Operation column on the Cluster page in the console.
secretKey
Role name, which can be copied on the Role Management page.
accessKey
Role token, which can be copied in the Token column on the Role Management page.


Subscribing to messages

do {
    List<Message> messages = null;

    try {
        // long polling of consumption messages
        // Long polling means that if the topic has no messages, the request will wait on the server for 3 seconds. If there is a message that can be consumed within 3 seconds, it will return immediately.
        messages = consumer.consumeMessage(
                Integer.parseInt(batchSize),
                Integer.parseInt(waitSeconds)
        );
    } catch (Throwable e) {
        e.printStackTrace();
    }
    if (messages == null || messages.isEmpty()) {
        System.out.println(Thread.currentThread().getName() + ": no new message, continue!");
        continue;
    }

    for (Message message : messages) {
        System.out.println("Receive message: " + message);
    }

    {
        List<String> handles = new ArrayList<String>();
        for (Message message : messages) {
            handles.add(message.getReceiptHandle());
        }

        try {
            consumer.ackMessage(handles);
        } catch (Throwable e) {
            if (e instanceof AckMessageException) {
                AckMessageException errors = (AckMessageException) e;
                System.out.println("Ack message fail, requestId is:" + errors.getRequestId() + ", fail handles:");
                if (errors.getErrorMessages() != null) {
                    for (String errorHandle :errors.getErrorMessages().keySet()) {
                        System.out.println("Handle:" + errorHandle + ", ErrorCode:" + errors.getErrorMessages().get(errorHandle).getErrorCode()
                                + ", ErrorMsg:" + errors.getErrorMessages().get(errorHandle).getErrorMessage());
                    }
                }
                continue;
            }
            e.printStackTrace();
        }
    }
} while (true);
Parameter
Description
batchSize
The number of messages pulled at a time. Maximum value: 16.
waitSeconds
The polling waiting time for a message pull. Maximum value: 30 seconds.

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