Introduction to grpc

https://grpc.io/docs/what-is-grpc/introduction/

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Introduce gRPC And protocol buffer .

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This page introduces you gRPC And protocol buffer .gRPC The protocol buffer can be used as its interface definition language ( IDL ) And the underlying message exchange format . If you are not familiar with it gRPC and / Or protocol buffer , Please read this ！ If you just want to know more about gRPC Operating condition , please Choose a language and try it Quick start.

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summary

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stay gRPC in , Client applications can directly call methods on server applications on different machines , It's like it's a local object , Make it easier for you to create distributed applications and services . And many RPC The system is the same ,gRPC The idea of service definition , Specify the methods that can be called remotely and their parameters and return types . On the server , The server implements this interface and runs a gRPC The client calls the server to handle . On the client side , The client has a stub （ In some languages, it's just called the client ）, It provides the same method as the server .

Concept map
gRPC Clients and servers can run and communicate with each other in a variety of environments —— from Google Internal server to your own desktop —— And you can use any gRPC Supported languages . therefore , for example , You can use Go、Python or Ruby The client in easily in Java Created in gRPC The server . Besides , Abreast of the times Google API Will have its interface gRPC edition , So that you can easily Google Build functionality into your application .

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Use protocol buffer

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By default ,gRPC Use protocol buffer , Google's mature open source mechanism for structured data serialization （ Although it can be used with other data formats such as JSON Use it together ）. This is a quick introduction to how it works . If you are already familiar with protocol buffers , Please feel free to jump to the next section .

The first step in using the protocol buffer is to define what to do in proto The structure of the serialized data in the file ： This is a .proto Ordinary text file with extension . The protocol buffer data is constructed as news , Each message is a small logical record of information , Contains a series of names called fields - It's worth it . This is a simple example ：

message Person {
    
  string name = 1;
  int32 id = 2;
  bool has_ponycopter = 3;
}

then , Once you specify your data structure , You can use the protocol buffer compiler protoc Generate data access classes from your prototype definition in your favorite language . These provide a simple accessor for each field , for example name()and set_name(), And serializing the entire structure / The method of parsing to the original bytes . therefore , for example , If the language you choose is C++, Running the compiler in the above example will generate a file named Person. then , You can use this class in your application to fill in 、 Serializing and retrieving Person Protocol buffer message .

You are in the ordinary proto The document defines gRPC service , take RPC Method parameters and return types are specified as protocol buffer messages ：

// The greeter service definition.
service Greeter {
    
  // Sends a greeting
  rpc SayHello (HelloRequest) returns (HelloReply) {
    }
}

// The request message containing the user's name.
message HelloRequest {
    
  string name = 1;
}

// The response message containing the greetings
message HelloReply {
    
  string message = 1;
}

gRPC Use protoc special gRPC Plug in from your proto File generation code ： You will get the generated gRPC Client and server code , And for filling 、 General protocol buffer code for serializing and retrieving message types . You'll see an example below .

To learn more about protocol buffers , Including how to protoc Install... In the language of your choice gRPC plug-in unit , Please refer to the protocol buffer documentation .

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Protocol buffer version

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The protocol buffer has been available to open source users for some time , Most examples of this site use the protocol buffer version 3 (proto3), It has a slightly simplified syntax 、 Some useful new features , And support more languages .Proto3 Currently in Protocol buffer GitHub The repository provides Java、C++、Dart、Python、Objective-C、C#、lite-runtime (Android Java)、Ruby and JavaScript edition , As well as from golang/protobuf Official package Go Language generator , More languages are being developed . You can go to proto3 More information and reference documents can be found in the language guide for each language . The reference document also includes a formal specification of .proto File format .

Generally speaking , Although you can use proto2（ Current default protocol buffer version ）, But we suggest that you will proto3 And gRPC Use it together , Because it allows you to use gRPC All supported languages , And avoid contact with proto2 Compatibility of client dialog proto3 The server , vice versa .