tencent cloud

Overview

This document describes how to use open-source SDK to send and receive messages by using the SDK for C++ as an example and helps you better understand the message sending and receiving processes.

Prerequisites

• You have created the required resources.
• You have installed GCC
• You have downloaded the demo

Directions

1. Prepare the environment.
   1. Install the Pulsar C++ client in the client environment as instructed in Pulsar C++ client.
   2. Introduce the files and dynamic libraries that are related to the Pulsar C++ client to the project.
2. Create a client.
   // Client configuration information
   ClientConfiguration config;
   // Set the role token
   AuthenticationPtr auth = pulsar::AuthToken::createWithToken(AUTHENTICATION);
   config.setAuth(auth);
   // Create a client
   Client client(SERVICE_URL, config);

   Parameter	Description
   SERVICE_URL	Cluster access address, which can be viewed and copied on the Cluster page in the console.
   AUTHENTICATION	Role token, which can be copied in the Token column on the Role Management page.

3. Create a producer.
   // Producer configurations
   ProducerConfiguration producerConf;
   producerConf.setBlockIfQueueFull(true);
   producerConf.setSendTimeout(5000);
   // Producer
   Producer producer;
   // Create a producer
   Result result = client.createProducer(
       // Complete path of the topic in the format of `persistent://cluster (tenant) ID/namespace/topic name`
       "persistent://pulsar-xxx/sdk_cpp/topic1",
       producerConf,
       producer);
   if (result != ResultOk) {
       std::cout << "Error creating producer: " << result << std::endl;
       return -1;
   }

   Note

   You need to enter the complete path of the topic name, i.e., persistent://clusterid/namespace/Topic, where the clusterid/namespace/topic part can be copied directly from the Topic page in the console.

4. Send the message.
   // Message content
   std::string content = "hello cpp client, this is a msg";
   // Create a message object
   Message msg = MessageBuilder().setContent(content)
       .setPartitionKey("mykey")  // Business key
       .setProperty("x", "1")   // Set message parameters
       .build();
   // Send the message
   Result result = producer.send(msg);
   if (result != ResultOk) {
       // The message failed to be sent
       std::cout << "The message " << content << " could not be sent, received code: " << result << std::endl;
   } else {
       // The message was successfully sent
       std::cout << "The message " << content << " sent successfully" << std::endl;
   }

5. Create a consumer.
   // Consumer configuration information
   ConsumerConfiguration consumerConfiguration;
   consumerConfiguration.setSubscriptionInitialPosition(pulsar::InitialPositionEarliest);
   // Consumer
   Consumer consumer;
   // Subscribe to a topic
   Result result = client.subscribe(
       // Complete path of the topic in the format of `persistent://cluster (tenant) ID/namespace/topic name`
       "persistent://pulsar-xxx/sdk_cpp/topic1",
       // Subscription name
       "sub_topic1",
       consumerConfiguration,
       consumer);
   
   if (result != ResultOk) {
       std::cout << "Failed to subscribe: " << result << std::endl;
       return -1;
   }

Note：

• You need to enter the complete path of the topic name, i.e., persistent://clusterid/namespace/Topic, where the clusterid/namespace/topic part can be copied directly from the Topic page in the console.
  
• You need to enter the subscription name in the subscriptionName parameter, which can be viewed on the Consumption Management page.

6. Consume the message.
   Message msg;
   // Obtain the message
   consumer.receive(msg);
   // Simulate the business processing logic
   std::cout << "Received: " << msg << "  with payload '" << msg.getDataAsString() << "'" << std::endl;
   // Return `ack` as the acknowledgement
   consumer.acknowledge(msg);
   // Return `nack` if the consumption fails, and the message will be delivered again
   // consumer.negativeAcknowledge(msg);

7. Log in to the TDMQ for Pulsar console, click Topic > Topic Name to enter the Consumption Management page, and click the triangle below a subscription name to view the production and consumption records.
   

Note：

The above is a brief introduction to the way of publishing and subscribing to messages. For more operations, see Demo or Pulsar C++ client.