What is gRPC?

gRPC is a high performance, open source universal RPC framework. By default, it uses Protocol Buffers.

Example

Prerequisites

• Golang
• Protocol Buffer compiler - protoc

sudo apt install protobuf-compiler

• Update PATH variable to include the path to the protoc executable
• Golang plugins

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

Creating gRPC services

The process of creating gRPC services follows three steps:

• Define Messages/Services
• Generate client/server source
• Implement gRPC service methods

Method types

There are four types of service methods that can be defined.

Unary RPC

These are the simplest RPCs where client sends single request to server and gets single response back:

rpc Method(RequestMessage) returns (ResponseMessage)

Server streaming

Server streaming RPCs where client sends single request, but gets a stream to read a sequence of messages. Example of this can be file download.

rpc Method(RequestMessage) returns (stream ResponseMessage)

Client streaming

In this case, the client sends a sequence of messages and once it’s finished, the server sends a single response. Example of this can be file upload.

rpc Method(stream RequestMessage) returns (ResponseMessage)

Bidirectional streaming

In this case, both client and server are sending a sequence of messages over two streams that operate independently.

rpc Method(stream RequestMessage) returns (stream ResponseMessage)

Protocol Buffers

syntax = "proto3"
package grpc-example;


service FileShare {
    rpc GetFileSize (GetFileSizeRequest) return (GetFileSizeResponse)
    rpc DownloadFile
    rpc UploadFile
    rpc GetAllFileSizes
}