Learning and remembering: RPC framework calling process

Introduction to RPC

RPC is the abbreviation of Remote Procedure Call. It is a protocol that requests services on a remote computer program through the network without having to understand the underlying network technology. No additional programming is required in the code, just like calling a local method directly.

RPC Framework Role

There are three important roles in the RPC framework: RPC Server, RPC Client and Registry, as shown in the following figure:

• RPC Server: Provider, the service provider that exposes the service
• RPC Client: Consumer, the service consumer that calls the remote service
• Registry: Service registration and discovery service registry

RPC core components

The RPC architecture consists of five core components: Client, Client Stub, Server, Server Stub, and NetWork Service. Stub can be understood as a stub.

• Client: The client, the caller of the service
• Client Stub: Client stub stores the address information of the server and is responsible for assembling the client's request information into a network message and sending it remotely to the service provider through the network.
• Server: The server, the real service provider
• Server Stub: The server stub receives messages from the client and decompresses the messages before calling local service methods.
• NetWork Service: underlying network transmission, which can be TCP or HTTP

RPC call process

The overall calling process of the RPC framework is shown in the following figure:

1. The client calls the remote interface service by local call;
2. After receiving the call, the client stub serializes the call information object and assembles it into a binary message body for network transmission;
3. The client sends messages to the remote server through Sockets;
4. After receiving the message, the server stub deserializes and decodes the network information object;
5. The server stub Server Stub calls the local interface service of the server according to the decoding result;
6. The local interface service is executed and the processing result is returned to the server stub Server Stub;
7. The server stub serializes the returned result object and assembles it into a message body;
8. The server then sends the message to the client through Sockets;
9. After receiving the result message, the client stub serializes and decodes the network information object;
10. The client obtains the final interface processing result.

The goal of the RPC architecture is to encapsulate steps 2, 3, 4, 7, 8, and 9 so that the caller feels like calling a local method.

Open source RPC framework

• Dubbo: The earliest open source RPC framework in China, developed by Alibaba and open sourced to the public at the end of 2011, only supports Java language
• Spring Cloud: Compared with RPC frameworks such as Dubbo, Spring Cloud provides a full set of distributed system solutions
• gRPC: It is a high-performance, general-purpose open source RPC framework developed by Google that supports multiple languages.