Myrpc version 0

RPC The concept of

Background knowledge

• RPC Basic concepts of , Core functions

common RPC frame

Duboo Basic function

1. Telematics
2. Transparent remote procedure call based on interface method
3. Load balancing
4. Service registry

RPC The process

client Call the remote method -> request serialize -> Protocol code -> Network transmission -> Server side -> Deserialization request -> Call the local method to get response -> serialize -> code ->……

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Version iteration process

Catalog

from 0 At the beginning RPC Iterative process of ：

• version0 edition ： Complete a with less than 100 lines of code RPC Example
• version1 edition ： Improve the common message format （request,response）, The client's dynamic proxy completes the request Encapsulation of message formats
• version2 edition ： Support the server to expose multiple service interfaces , Server program abstraction , Normalization
• version3 edition ： Use a high-performance network framework netty The realization of network communication , And the refactoring of client code
• version4 edition ： Custom message format , Support multiple serialization methods （java Native , json…）
• version5 edition : Implementation of server registration and discovery ,zookeeper As a registry
• version6 edition : Implementation of load balancing strategy

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0. One of the simplest RPC call

Background knowledge

• java Basics
• java socket Introduction to programming
• Project use maven build , For the time being, only lombok package

Questions in this section

• What is? RPC, How to complete one RPC?

One RPC The simplest The process is client side call A method of the server , The server returns the return value of the execution method to the customer service . Next, I will use an example of fetching data from a database to conduct a simulation RPC A complete process of the process .

Assume There is such a service ：

Server side ：

1. There is one User surface

   2. UserServiceImpl Realized UserService Interface
   3. UserService There is only one function in the : getUserByUserId(Integer id)

client ：

​ Pass a Id To the server , The server finds User Object returned to client

The process

1. First we have to have User object , This is known to both the client and the server , The client needs to get this pojo Object data , The server needs to operate this object

@Builder
@Data
@NoArgsConstructor
@AllArgsConstructor
public class User implements Serializable {
    
    //  Both client and server share 
    private Integer id;
    private String userName;
    private Boolean sex;
}

2. To define the client, you need to call , The service interface that the server needs to provide

public interface UserService {
    
    //  The client calls the implementation class of the server through this interface 
    User getUserByUserId(Integer id);
}

3. The server needs to implement Service Function of interface

public class UserServiceImpl implements UserService {
    
    @Override
    public User getUserByUserId(Integer id) {
    
        System.out.println(" The client inquired "+id+" Users of ");
        //  Simulate the behavior of fetching users from the database 
        Random random = new Random();
        User user = User.builder().userName(UUID.randomUUID().toString())
                .id(id)
                .sex(random.nextBoolean()).build();
        return user;
    }
}

4. Client creation Socket Connect , transmission Id To the server , Get back User object

public class RPCClient {
    
    public static void main(String[] args) {
    
        try {
    
            //  establish Socket Connect 
            Socket socket = new Socket("127.0.0.1", 8899);
            ObjectOutputStream objectOutputStream = new ObjectOutputStream(socket.getOutputStream());
            ObjectInputStream objectInputStream = new ObjectInputStream(socket.getInputStream());
            //  To the server id
            objectOutputStream.writeInt(new Random().nextInt());
            objectOutputStream.flush();
            //  Server query data , Returns the corresponding object 
            User user  = (User) objectInputStream.readObject();
            System.out.println(" Returned by the server User:"+user);
        } catch (IOException | ClassNotFoundException e) {
    
            e.printStackTrace();
            System.out.println(" Client failed to start ");
        }
    }
}

5. Server side BIO Mode of monitoring Socket, If you have data , Call the implementation class of the corresponding service to execute the task , Returns the result to the client

public class RPCServer {
    
    public static void main(String[] args) {
    
        UserServiceImpl userService = new UserServiceImpl();
        try {
    
            ServerSocket serverSocket = new ServerSocket(8899);
            System.out.println(" The server has started ");
            // BIO Mode of monitoring Socket
            while (true){
    
                Socket socket = serverSocket.accept();
                //  Start a thread to process 
                new Thread(()->{
    
                    try {
    
                        ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());
                        ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());
                        //  Read from the client id
                        Integer id = ois.readInt();
                        User userByUserId = userService.getUserByUserId(id);
                        //  write in User Object to the client 
                        oos.writeObject(userByUserId);
                        oos.flush();
                    } catch (IOException e){
    
                        e.printStackTrace();
                        System.out.println(" from IO Error reading data in ");
                    }
                }).start();
            }
        } catch (IOException e) {
    
            e.printStackTrace();
            System.out.println(" Server start failed ");
        }
    }
}

result ：

summary ：

This example takes less than a hundred lines of code , A remote procedure call between client and server is realized , Very suitable for getting started , Of course it is And its imperfections Of , Even the message format is not unified , We will gradually improve it in the next version update .

this RPC The biggest pain point of ：

1. Only the server can be called Service The only sure way , What if there are two methods to call ?（Reuest Need to be abstract ）
2. The return value only supports User object , If you need to pass a string or a Dog,String What about objects? （Response Need to be abstract ）
3. The client is not universal enough ,host,port, Is specific to the method being called （ Need to be abstract ）

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