ApsaraMQ for RocketMQ:Send and receive ordered messages

Background information

For more information, see Ordered messages.

Prerequisites

Before you start, make sure that the following operations are performed:

• Install the SDK for Go. For more information, see Prepare the environment.

• Create the resources that you want to specify in the code in the ApsaraMQ for RocketMQ console. The resources include instances, topics, and consumer groups. For more information, see Create resources.

• Obtain the AccessKey pair of your Alibaba Cloud account. For more information, see Create an AccessKey pair.

Send ordered messages

The following sample code provides an example on how to send ordered messages by using the HTTP client SDK for Go:

package main

import (
    "fmt"
    "time"
    "strconv"
    "os"

    "github.com/aliyunmq/mq-http-go-sdk"
)

func main() {
    // The HTTP endpoint. You can obtain the endpoint in the HTTP Endpoint section of the Instance Details page in the ApsaraMQ for RocketMQ console. 
    endpoint := "${HTTP_ENDPOINT}"
    // Make sure that the environment variables ALIBABA_CLOUD_ACCESS_KEY_ID and ALIBABA_CLOUD_ACCESS_KEY_SECRET are configured. 
    // The AccessKey ID that is used for authentication. 
    accessKey := os.Getenv("ALIBABA_CLOUD_ACCESS_KEY_ID")
    // The AccessKey secret that is used for authentication. 
    secretKey := os.Getenv("ALIBABA_CLOUD_ACCESS_KEY_SECRET")
    // The topic in which the message is produced. You must create the topic in the ApsaraMQ for RocketMQ console. 
    topic := "${TOPIC}"
    // The ID of the instance to which the topic belongs. You must create the instance in the ApsaraMQ for RocketMQ console. 
    // If the instance has a namespace, specify the ID of the instance. If the instance does not have a namespace, set the instanceID parameter to null or an empty string. You can obtain the namespace of the instance on the Instance Details page in the ApsaraMQ for RocketMQ console. 
    instanceId := "${INSTANCE_ID}"

    client := mq_http_sdk.NewAliyunMQClient(endpoint, accessKey, secretKey, "")

    mqProducer := client.GetProducer(instanceId, topic)
    // Cyclically send eight messages. 
    for i := 0; i < 8; i++ {
        msg := mq_http_sdk.PublishMessageRequest{
            MessageBody: "hello mq!",         // The message content. 
            MessageTag:  "",                  // The message tag. 
            Properties:  map[string]string{}, // The message attributes. 
        }
        // The message key. 
        msg.MessageKey = "MessageKey"
        // The custom attributes of the message. 
        msg.Properties["a"] = strconv.Itoa(i)
        // The sharding key that is used to distribute ordered messages to a specific partition. Sharding keys can be used to identify partitions. A sharding key is different from a message key. 
        msg.ShardingKey = strconv.Itoa(i % 2)
        ret, err := mqProducer.PublishMessage(msg)

        if err != nil {
            fmt.Println(err)
            return
        } else {
            fmt.Printf("Publish ---->\n\tMessageId:%s, BodyMD5:%s, \n", ret.MessageId, ret.MessageBodyMD5)
        }
        time.Sleep(time.Duration(100) * time.Millisecond)
    }
}

Subscribe to ordered messages

The following sample code provides an example on how to subscribe to ordered messages by using the HTTP client SDK for Go:

package main

import (
    "fmt"
    "github.com/gogap/errors"
    "strings"
    "time"
    "os"

    "github.com/aliyunmq/mq-http-go-sdk"
)

func main() {
    // The HTTP endpoint. You can obtain the endpoint in the HTTP Endpoint section of the Instance Details page in the ApsaraMQ for RocketMQ console. 
    endpoint := "${HTTP_ENDPOINT}"
    // Make sure that the environment variables ALIBABA_CLOUD_ACCESS_KEY_ID and ALIBABA_CLOUD_ACCESS_KEY_SECRET are configured. 
    // The AccessKey ID that is used for authentication. 
    accessKey := os.Getenv("ALIBABA_CLOUD_ACCESS_KEY_ID")
    // The AccessKey secret that is used for authentication. 
    secretKey := os.Getenv("ALIBABA_CLOUD_ACCESS_KEY_SECRET")
    // The topic in which the message is produced. You must create the topic in the ApsaraMQ for RocketMQ console. 
    topic := "${TOPIC}"
    // The ID of the instance to which the topic belongs. You must create the instance in the ApsaraMQ for RocketMQ console. 
    // If the instance has a namespace, specify the ID of the instance. If the instance does not have a namespace, set the instanceID parameter to null or an empty string. You can obtain the namespace of the instance on the Instance Details page in the ApsaraMQ for RocketMQ console. 
    instanceId := "${INSTANCE_ID}"
    // The ID of the consumer group that you created in the ApsaraMQ for RocketMQ console. 
    groupId := "${GROUP_ID}"

    client := mq_http_sdk.NewAliyunMQClient(endpoint, accessKey, secretKey, "")

    mqConsumer := client.GetConsumer(instanceId, topic, groupId, "")

    for {
        endChan := make(chan int)
        respChan := make(chan mq_http_sdk.ConsumeMessageResponse)
        errChan := make(chan error)
        go func() {
            select {
            case resp := <-respChan:
                {
                    // The message consumption logic. 
                    var handles []string
                    fmt.Printf("Consume %d messages---->\n", len(resp.Messages))
                    for _, v := range resp.Messages {
                        handles = append(handles, v.ReceiptHandle)
                        fmt.Printf("\tMessageID: %s, PublishTime: %d, MessageTag: %s\n"+
                            "\tConsumedTimes: %d, FirstConsumeTime: %d, NextConsumeTime: %d\n"+
                            "\tBody: %s\n"+
                            "\tProps: %s\n"+
                            "\tShardingKey: %s\n",
                            v.MessageId, v.PublishTime, v.MessageTag, v.ConsumedTimes,
                            v.FirstConsumeTime, v.NextConsumeTime, v.MessageBody, v.Properties, v.ShardingKey)
                    }

                    // If the broker fails to receive an acknowledgment (ACK) for a message from the consumer before the period of time specified by the NextConsumeTime parameter elapses, the broker delivers the message in the partition to the consumer again. 
                    // A unique timestamp is specified for the handle of a message each time the message is consumed. 
                    ackerr := mqConsumer.AckMessage(handles)
                    if ackerr != nil {
                        // If the handle of the message times out, the broker fails to receive an ACK for the message from the consumer. 
                        fmt.Println(ackerr)
                        if errAckItems, ok := ackerr.(errors.ErrCode).Context()["Detail"].([]mq_http_sdk.ErrAckItem); ok {
                           for _, errAckItem := range errAckItems {
                              fmt.Printf("\tErrorHandle:%s, ErrorCode:%s, ErrorMsg:%s\n",
                                 errAckItem.ErrorHandle, errAckItem.ErrorCode, errAckItem.ErrorMsg)
                           }
                        } else {
                           fmt.Println("ack err =", ackerr)
                        }
                        time.Sleep(time.Duration(3) * time.Second)
                    } else {
                        fmt.Printf("Ack ---->\n\t%s\n", handles)
                    }

                    endChan <- 1
                }
            case err := <-errChan:
                {
                    // No message is available for consumption in the topic. 
                    if strings.Contains(err.(errors.ErrCode).Error(), "MessageNotExist") {
                        fmt.Println("\nNo new message, continue!")
                    } else {
                        fmt.Println(err)
                        time.Sleep(time.Duration(3) * time.Second)
                    }
                    endChan <- 1
                }
            case <-time.After(35 * time.Second):
                {
                    fmt.Println("Timeout of consumer message ??")
                    endChan <- 1
                }
            }
        }()

                // The consumer may pull partitionally ordered messages from multiple partitions. The consumer consumes the messages in each partition in the order in which the messages are sent. 
                // Assume that the consumer pulls partitionally ordered messages from one partition. If the broker does not receive an ACK for a message from the consumer, the broker delivers the message to the consumer again. 
                // The consumer can consume the next batch of messages from a partition only after all messages that are pulled from the partition in the previous batch are acknowledged to be consumed. 
                // Consume messages in long polling mode. In long polling mode, the network timeout period is 35 seconds. 
                // In long polling mode, if no message is available for consumption in the topic, requests are suspended on the broker for the specified period of time. If a message becomes available for consumption during the specified period of time, the broker immediately sends a response to the consumer. In this example, the value is specified as 3 seconds. 
        mqConsumer.ConsumeMessageOrderly(respChan, errChan,
            3, // The maximum number of messages that can be consumed at a time. In this example, the value is specified as 3. The maximum value that you can specify is 16. 
            3, // The duration of a long polling period. Unit: seconds. In this example, the value is specified as 3. The maximum value that you can specify is 30. 
        )
        <-endChan
    }
}