How to use Golang to implement message forwarding

Golang is an efficient, concise and powerful programming language with perfect concurrency control mechanism and rich standard library functions. It has been widely used in cloud computing, network programming, distributed systems, microservices and other fields. In these application scenarios, message forwarding is a very important function. This article introduces how to use Golang to implement message forwarding.

1. Message model

In message forwarding applications, the most important thing is the message model. The message model refers to the data structure and interaction method used to deliver messages in the system. Normally, a message model should have the following characteristics:

1.1 Flexibility

The message model needs to have a certain degree of flexibility to support various message types. For example, a message may be text, binary data, picture, video, etc.

1.2 Reliability

The message model needs to have a certain degree of reliability to ensure the delivery of the message. In a distributed system, a message may need to pass through multiple network nodes to reach the destination node. Therefore, it is necessary to ensure that messages are not lost due to network problems or other abnormal conditions.

1.3 Efficiency

The message model needs to have a certain degree of efficiency to ensure system performance and user experience. In message forwarding applications, messages need to be sent to the target node quickly without causing system freezes or delays due to message transmission.

Based on the above characteristics, we can design a basic message model, as shown in the following figure:

The message model in the figure includes the following parts ：

• Message header: Contains meta-information of the message, such as message type, sender ID, receiver ID, etc.
• Message body: Contains the actual content of the message, such as text, pictures, binary data, etc.
• Message queue: used to cache messages to ensure stable delivery of messages. This can be achieved using queue technologies such as Redis, Kafka, and RocketMQ.
• Message routing: used to send messages to the target node, which can be implemented using RPC, HTTP and other protocols.

2. Implementation of message forwarding

After the design of the message model is completed, we need to consider the specific implementation of message forwarding. Generally speaking, the following two methods can be used for message forwarding:

2.1 Point-to-point method

The point-to-point method means that the message sender directly sends the message to the message receiver. The advantages of this method are simple implementation and fast message transmission. However, in a distributed system, it may encounter problems such as node failure and network packet loss, resulting in the failure of messages to be delivered correctly.

2.2 Publish-subscribe method

The publish-subscribe method refers to sending messages to a central message server, and then subscribers (receivers) subscribe to the messages they are interested in from the server. The advantage of this method is that the reliability of the message is high, and problems such as node failures can be automatically handled by the central server. The disadvantage is that the implementation is relatively complex and will increase a certain network transmission delay.

Below we will use Golang to implement a message forwarding module based on publish and subscribe. We will use Redis as the message queue and the RPC protocol for message routing.

2.3 Message queue design

Redis is a fast and stable memory cache database that can also be used as a message queue. The following is the core code fragment for using Redis as a message queue:

type RedisBroker struct {
    client *redis.Client
    topic  string
}

func NewRedisBroker(address, password, topic string) *RedisBroker {
    client := redis.NewClient(&redis.Options{
        Addr:     address,
        Password: password,
    })

    return &RedisBroker{
        client: client,
        topic:  topic,
    }
}

func (b *RedisBroker) Publish(msg *Message) error {
    data, err := json.Marshal(msg)
    if err != nil {
        return err
    }

    _, err = b.client.LPush(b.topic, data).Result()
    if err != nil {
        return err
    }

    return nil
}

func (b *RedisBroker) Subscribe() (<p>In the above code, we implemented a structure called RedisBroker, which encapsulates the LPush and Subscribe methods of Redis and is used to send messages to the message queue respectively. Push messages and subscribe to message queues. After the Broker instance is created, you can use the Publish method to push messages to the Redis queue, and the Subscribe method to subscribe to messages in the Redis queue. In the message processing function, we will parse the Message object in the Redis message and send it to the RPC service. </p><p>2.4 Message routing design</p><p>RPC protocol is a remote procedure call protocol based on TCP/IP protocol. It delivers function calls to remote nodes through the network and returns results. We will use the RPC protocol to implement message routing. The following is the core code snippet based on the gRPC implementation: </p><pre class="brush:php;toolbar:false">type Server struct {
    brok *RedisBroker
}

func (s *Server) Send(ctx context.Context, msg *proto.Message) (*proto.Response, error) {
    log.Printf("Receive message from %v to %v: %v", msg.Sender, msg.Receiver, msg.Text)

    // Publish message to Redis
    err := s.brok.Publish(&Message{
        Sender:   msg.Sender,
        Receiver: msg.Receiver,
        Text:     msg.Text,
    })
    if err != nil {
        log.Println("failed to publish message:", err)
    }

    return &proto.Response{Ok: true}, nil
}

func StartRPCService(address string, brok *RedisBroker) {
    lis, err := net.Listen("tcp", address)
    if err != nil {
        log.Fatalf("failed to listen: %v", err)
    }

    s := grpc.NewServer()

    proto.RegisterMessageServiceServer(s, &Server{
        brok: brok,
    })

    log.Println("start rpc service at", address)

    if err := s.Serve(lis); err != nil {
        log.Fatalf("failed to serve: %v", err)
    }
}

In the above code, we implemented a Server structure based on the gRPC protocol, which encapsulates the Send method for Send received messages to Redis queue. In the Send method, we will parse the gRPC message and convert it into a Message object, and then send the message to the Redis queue through the Publish method of RedisBroker. When starting the RPC service, we start the RPC service through the s.Serve method and listen for TCP connections on the address address.

3. Usage Example

Now that we have implemented the message forwarding module based on publish and subscribe, we can test it. We can start the RPC service in the terminal:

func main() {
    // New Redis broker
    broker := NewRedisBroker("localhost:6379", "", "go-message-broker")

    // Start RPC service
    StartRPCService(":9090", broker)
}

Then write a client program, implement the receiver in the client program, and subscribe to the message with the receiver ID "receiver-01" from the Redis queue:

func main() {
    // New Redis broker
    broker := NewRedisBroker("localhost:6379", "", "go-message-broker")

    // Receive message
    ch, err := broker.Subscribe()
    if err != nil {
        log.Fatal("subscribe error:", err)
    }

    for {
        select {
        case message := <p>At the same time, we also need a sender to simulate the behavior of sending messages: </p><pre class="brush:php;toolbar:false">func main() {
    // New RPC client
    conn, err := grpc.Dial(":9090", grpc.WithInsecure())
    if err != nil {
        log.Fatalf("did not connect: %v", err)
    }
    defer conn.Close()

    c := proto.NewMessageServiceClient(conn)

    // Send message
    _, err = c.Send(context.Background(), &proto.Message{
        Sender:   "sender-01",
        Receiver: "receiver-01",
        Text:     "hello go message broker",
    })
    if err != nil {
        log.Fatalf("could not send message: %v", err)
    }
}

Run the above three programs, the sender sends a message, the receiver will receive the message, and at the same time, you can Related log output is seen on the sender's and receiver's terminals.

4. Summary

This article introduces how to use Golang to implement a message forwarding module based on publish and subscribe. By using Redis queue and RPC protocol, we have implemented an efficient, flexible and reliable message forwarding system. Of course, this is just a simple implementation. In actual production environments, more issues need to be dealt with, such as message signatures, security guarantees, load balancing, etc. However, by studying the content described in this article, you can master Golang's core technologies and ideas in message transmission, and provide support for the development of more efficient and reliable distributed systems.

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