upasana05ghosh / gRPC-In-Go-Lang

Basic gRPC call In Go Lang

gRPC-In-Go-Lang

• gRPC-In-Go-Lang
  • What is gRPC?
    • RPC
    • gRPC
    • Why it's getting popular?
    • Wait, what is HTTP/2 protocol?
    • I heard people are using it instead of REST API.
    • Why not keep using REST?
• Basic gRPC call In Go Lang
  • Create proto file
  • Write gRPC server code
  • How to test our grpc end point

Table of contents generated with markdown-toc

What is gRPC?

It's google RPC. :sweat_smile:
Hey, I know about google. But what is RPC?

RPC

• It stands for Remote Procedural Call.
• It uses a form of function call instead of the popular HTTP calls.
• It uses IDL(Interface Definition Lang.) as a form of contract.

gRPC

• It's a google RPC.
• It uses HTTP/2 protocol.
• It uses Protocol Buffer (ProtoBuf) format for sending/receiving messages.

Why it's getting popular?

• Easy - It's a simple function call.
• Support - It is supported in a lot of languages.
• Fast - It uses HTTP/2 protocol.

Wait, what is HTTP/2 protocol?

• Well it's HTTP version 2. 🤦
• It's faster than HTTP 1 as it comes with the following features:
  • Enable request and response multiplexing - Servers can send multiple messages in a single request.
  • Header compression
  • binary protocol - Send message in 0/1 format instead of text-based format
• It uses Protocol Buffer (ProtoBuf) as the IDL.

I heard people are using it instead of REST API.

• Well REST is an architectural style.
• It defines protocols to talk between client and server.
• It uses HTTP/1 protocol.
• It uses JSON format for sending/receiving messages.

Why not keep using REST?

• Well it's simple, easy to use and there are many tools to test it easily.
• Issues:
  • Sometimes the payload becomes huge and it decreases the performance.
  • It's unary, that is we can send one request at a time.
  • REST uses HTTP/1 protocol which does three-way handshaking for the first message, making it slower.

Note: It's best to use REST when communicating between browser and back-end. gRPC is best for inter-microservice communication.

Basic gRPC call In Go Lang

Create proto file

1. Create go.mod file go mod init github.com/ughosh/grcp-learn

2. Create a file hello.proto

3. In add hello.proto

   1. Add the version of proto file

          syntax = "proto3"; 
      

   2. Add folder name where we want to save generated files

        option go_package = "github.com/ughosh/grcp-learn/invoicer";
      

   3. Define service

   service Invoicer {
       rpc Hello(HelloRequest) returns (HelloResponse);
   } 
   

   4. Define request and response as message

   message HelloRequest{
       string name = 1;
   }
   
   message HelloResponse {
   string msg = 1;
   }
   

4. Create a folder name hello

5. Run the command to generate proto files based on the description given in our hello.proto file

   protoc \
   --go_out=hello \
   --go_opt=paths=source_relative \
   --go-grpc_out=hello \
   --go-grpc_opt=paths=source_relative \
   hello.proto
   

6. If error occur, try running

   go install google.golang.org/grpc/cmd/protoc-gen-go-grpc@lates
   

7. The generate file will be showing some error, in case the lib is not present. Do go mod tidy after this to clean-up go.mod file

    go get -u google.golang.org/grpc
   

8. If we make any changes in our hello.proto file, we have to run command #5. To save our time, we can save the entire command in Makefile. Create a Makefile and add the command

 generate_grpc_code_hello:
 protoc \
 --go_out=hello \
 --go_opt=paths=source_relative \
 --go-grpc_out=hello \
 --go-grpc_opt=paths=source_relative \
 hello.proto

Now, if we want to do any updates, run make generate_grpc_code_hello

Write gRPC server code

Add main.go file and run that file using go run main.go This will start our server which is listening to port 8080

How to test our grpc end point

To test it, we will be using grpcurl (https://github.com/fullstorydev/grpcurl) Run the command in another terminal

grpcurl -plaintext -d '{"name": "Test"}' localhost:8080 Hello.Hello

You will output like

  {
      "msg": "Hello Test"
  }

Congratulations! You created your first gRPC call in Go lang 🎉