RPC procedure

This paper belongs to 【 Tamp Dubbo】 Series articles , The series is designed to use easy to understand language , Take you to know and learn Dubbo technology , Hope to bring some dry goods to the readers . The catalogue of the series is as follows （ Maybe as the writing goes on , Will make some adjustments ）：

【 Tamp Dubbo】 What is? RPC frame ？
【 Tamp Dubbo】Dubbo The core feature of
【 Tamp Dubbo】Dubbo The architecture and zookeeper Registration center construction and configuration
【 Tamp Dubbo】Dubbo and Spring Boot Integration to complete service registration
【 Tamp Dubbo】Dubbo Configuration summary of
【 Tamp Dubbo】Dubbo Load balancing settings for
【 Tamp Dubbo】Dubbo Service fusing and degradation treatment
【 Tamp Dubbo】Dubbo The core principle of

This article is mainly to share what is RPC frame , About RPC The explanation of , There are a lot of information on the Internet , To ensure the integrity of the tutorial , I'd like to share it here , At the same time, I also consolidate myself . Introducing RPC Before , First, let's see how our tradition is called .

For example, now I want to call a method , Get the order information , So in traditional projects , It's usually called directly , as follows ：

Now? , Based on the consideration of high performance and high reliability , You decide to transform the system into a distributed application , A lot of functions that can be shared are brought out by themselves , For example, the order information mentioned above , You put it in a service alone , Let other services call it . So it's like this ：

Here comes the question , service A There is no OrderServiceImpl This class , So how does it call services B Of OrderServiceImpl Of get Methods? ？ This can be used to RPC frame 了 , So we know ,RPC The framework is mainly used to solve two problems ：

1. Solve the problem in distributed system , Call between services .
2. When called remotely , It should be as convenient as local call , Make the caller imperceptible to the logic of the remote call .

Let's see RPC How to explain ：Remote Procedure Call, Remote procedure call , It is a way of inter process communication , It's a technical idea , Not a norm . It allows the program to call another address space （ Usually on another machine that shares the network ） A process or function of , Instead of programmers explicitly coding the details of this remote call . That is, whether the programmer calls local or remote functions , Essentially, the call code written is basically the same . So the details don't matter to programmers .

Let's see RPC What has been done inside the framework , Quote the pictures on the Internet ：

As can be seen from this picture , Whole RPC The call procedure of the involves a procedure and several concepts , Let's summarize ：

1. Client： Calling end , Call the service locally , It's equivalent to the above Server A.
2. client stub： Responsible for receiving the call 、 The parameters are assembled into a message body capable of network transmission （ serialize ）;client stub Find the service address , And send the message to the server .
3. server stub： Decode the message upon receipt , Deserialization ;server stub The local service is invoked based on the decoding results ; The local service executes and returns the result to server stub.server stub The returned result is packaged into a message and sent to the consumer .
4. client stub Message received , And decode it , Deserialization , Service consumers get the end result .

This process , We can use a flowchart to represent , It will be more intuitive ：

So you can see ,RPC The two core modules of are ： Communication and serialization .RPC There are a lot of , such as ：Dubbo、gRPC、Thrift、HSF wait , Let me summarize Dubbo Use .