Introduction to gRPC

by Michał Pawlik

code::dive 2019

A high performance, open-source universal RPC framework

An interprocess communication technique that is used for client-server based applications.

RPC

REST

JSON over HTTP/1.1

sounds similar to...

REpresentational State Transfer

Advantages

  • Easy to learn
  • Simple to implement
  • Common
  • Human readable serialization format

Drawbacks

  • No documentation support built-in
  • Requires boilerplate
  • Bad support for versioning
  • No type safety
  • Inefficient format, CPU intensive compression
  • No built-in support for pagination
  • No valid way to trigger actions

Example OpenAPI definition

paths:
  /pet:
    post:
      tags:
      - "pet"
      summary: "Add a new pet to the store"
      description: ""
      operationId: "addPet"
      consumes:
      - "application/json"
      - "application/xml"
      produces:
      - "application/xml"
      - "application/json"
      parameters:
      - in: "body"
        name: "body"
        description: "Pet object that needs to be added to the store"
        required: true
        schema:
          $ref: "#/definitions/Pet"
      responses:
        405:
          description: "Invalid input"
      security:
      - petstore_auth:
        - "write:pets"
        - "read:pets"
    put:
      tags:
      - "pet"
      summary: "Update an existing pet"
      description: ""
      operationId: "updatePet"
      consumes:
      - "application/json"
      - "application/xml"
      produces:
      - "application/xml"
      - "application/json"
      parameters:
      - in: "body"
        name: "body"
        description: "Pet object that needs to be added to the store"
        required: true
        schema:
          $ref: "#/definitions/Pet"
      responses:
        400:
          description: "Invalid ID supplied"
        404:
          description: "Pet not found"
        405:
          description: "Validation exception"
      security:
      - petstore_auth:
        - "write:pets"
        - "read:pets"

Sample from https://editor.swagger.io/

gRPC

Alternative to REST?

We'll see...

Handful of facts

gRPC Remote Procedure Calls

gRPC background

  • Free and open source since 2015
  • Built by Google - successor to internal RPC platform called Stubby
  • Project of CNCF (Cloud Native Computing Foundation)
  • Adopted in production by Google, Salesforce, Netflix, Spotify and more
  • Uses protocol buffers for serialization

gRPC principles

  • Based on services and messages
  • Cross platform
  • Built-in streaming support
  • Pluggable security, metrics, health checks using interceptors
  • Versioning support
  • Layered - key facets of the stack must be able to evolve independently

Compared to other RPCs

  • Asynchronous, non-blocking - supports distributed systems
  • Very simple to define - just define and compile protobuf
  • Message-based, no shared or mutable state
  • Open source, based on standards

gRPC communication

Protobuf

Protocol buffers are Google's language-neutral, platform-neutral, extensible mechanism for serializing structured data – think XML, but smaller, faster, and simpler.

~developers.google.com

Let's try it out

Protobuf syntax

syntax = "proto3";
package example;

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

message Product {
    int64 id = 			 	1;
    string name =		 	2;
    double price =		 	3;
    map<string,string> properties =	4;
}

message EmptyMessage {}
service ExampleService {
  rpc RequestResponse(MyRequestMsg) returns (MyResponseMsg) {}
  rpc ClientStreaming(stream MyRequestMsg) returns (MyResponseMsg) {}
  rpc ServerStreaming(MyRequestMsg) returns (stream MyResponseMsg) {}
  rpc BiDiStreaming(stream MyRequestMsgg) returns (stream MyResponseMsg) {}
}

Message definition

Tag numbers

Service definition

Sample service

  • Define a product
  • Expose product listing method

Sample service

// file name: shop.proto

syntax = "proto3";
package grpc_introduction;

message Product {
    int64 id = 				1;
    string name =			2;
    string description =		3;
    double price =			4;
    map<string,string> properties =	5;
}

message ProductsListRequest {}

service ShopServer {
    rpc GetProducts (ProductsListRequest) returns (stream Product);
}

Implementation

Example in Go

Install dev tools

$ sudo dnf -y install protoc # or alike for your system
$ go get -u github.com/golang/protobuf/protoc-gen-go

Compile protobuf

$ protoc --go_out=. ./grpc_introduction/shop.proto

Import in code

package main

import (
	pb "grpc_introduction"
	"google.golang.org/grpc"
)

/* Rest of the code */

Output

package grpc_introduction

import (
	fmt "fmt"
	proto "github.com/golang/protobuf/proto"
	math "math"
)
/*
 ... skipped ...
*/

type Product struct {
	Id                   int64             `protobuf:"varint,1,opt,name=id,proto3" json:"id,omitempty"`
	Name                 string            `protobuf:"bytes,2,opt,name=name,proto3" json:"name,omitempty"`
	Description          string            `protobuf:"bytes,3,opt,name=description,proto3" json:"description,omitempty"`
	Price                float64           `protobuf:"fixed64,4,opt,name=price,proto3" json:"price,omitempty"`
	Properties           map[string]string `protobuf:"bytes,5,rep,name=properties,proto3" json:"properties,omitempty" protobuf_key:"bytes,1,opt,name=key,proto3" protobuf_val:"bytes,2,opt,name=value,proto3"`
	XXX_NoUnkeyedLiteral struct{}          `json:"-"`
	XXX_unrecognized     []byte            `json:"-"`
	XXX_sizecache        int32             `json:"-"`
}

Building server

type shopServer struct {
	products []*pb.Product
}
func (s *shopServer) registerProduct(p *pb.Product) {
	s.products = append(s.products, p)
}
func (s *shopServer) GetProducts(req *pb.ProductsListRequest, stream pb.ShopServer_GetProductsServer) error {
	for _, p := range s.products {
		if err := stream.Send(p); err != nil {
			return err
		}
	}
	log.Println("Products delivered")
	return nil
}
func main() {
	lis, _ := net.Listen("tcp", fmt.Sprintf(":%d", 9090))
	log.Println("Listening on", lis.Addr())
	grpcServer := grpc.NewServer()
	svr := &shopServer{}
	for i := 0; i < 20; i++ {
		p := pb.Product{
			Name: fmt.Sprintf("Product-%d", i),
			Id:   int64(i),
		}
		svr.registerProduct(&p)
	}
	pb.RegisterShopServerServer(grpcServer, svr)
	grpcServer.Serve(lis)
}

Building client

func main() {
	conn, _ := grpc.Dial("localhost:9090", grpc.WithInsecure())
	client := pb.NewShopServerClient(conn)
	ctx, _ := context.WithTimeout(context.Background(), 30*time.Second)
	stream, _ := client.GetProducts(ctx, &pb.ProductsListRequest{})
	products := make([]*pb.Product, 0)
	for {
		product, err := stream.Recv()
		if err == io.EOF {
			break
		}
		if err != nil {
			log.Fatal(err)
		}
		products := append(products, product)
	}
	log.Println(products)
}

Server build and run

$ go build
$ ./server
2019/09/17 11:06:36 Listening on [::]:9090

Client build and run

$ go build
$ ./client
2019/09/17 11:09:47 [name:"Product-0"  id:1 name:"Product-1"  id:2 name:"Product-2"  id:3 name:"Product-3"  id:4 name:"Product-4"  id:5 name:"Product-5"  id:6 name:"Product-6"  id:7 name:"Product-7"  id:8 name:"Product-8"  id:9 name:"Product-9"  id:10 name:"Product-10"  id:11 name:"Product-11"  id:12 name:"Product-12"  id:13 name:"Product-13"  id:14 name:"Product-14"  id:15 name:"Product-15"  id:16 name:"Product-16"  id:17 name:"Product-17"  id:18 name:"Product-18"  id:19 name:"Product-19" ]
$ go build
$ ./server
2019/09/17 11:06:36 Listening on [::]:9090
2019/09/17 11:06:38 Products delivered

How about Python?

import grpc

import shop_pb2
import shop_pb2_grpc

channel = grpc.insecure_channel('localhost:9090')
stub = shop_pb2_grpc.ShopServerStub(channel)
products = stub.GetProducts(shop_pb2.ProductsListRequest())
for product in products:
    print(product.name, product.id)

Compile protobuf

$ mkdir python-client
$ cp shop.proto python-client
$ cd python-client
$ virtualenv -p python3 .venv
$ pip install grpcio grpcio-tools
$ python -m grpc_tools.protoc -I=. --python_out=. --grpc_python_out=. shop.proto
# shop_pb2_grpc.py and shop_pb2.py are now generated in current directory

Implement client

Run it!

$ python main.py
Product-0 0
Product-1 1
Product-2 2
Product-3 3
Product-4 4
Product-5 5
Product-6 6
Product-7 7
Product-8 8
Product-9 9
Product-10 10
Product-11 11
Product-12 12
Product-13 13
Product-14 14
Product-15 15
Product-16 16
Product-17 17
Product-18 18
Product-19 19

Other languages?

  • Supported officially

    • C++

    • Java

    • Python

    • Dart

    • Objective C

    • Go

    • Ruby

    • Node.js

    • Dart

    • C#

    • PHP

  • And many more community driven

Summing up

Benefits of gRPC

  • Protocol first
  • Type safety
  • Polyglot
  • Easy to bootstrap
  • Compared to JSON:
    • Smaller messages
    • less CPU-intensive

Thank you!

Questions?

Contact me:

Keybase: @majkp

Homepage: https://michalp.net/

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