end-to-end-grpc-gateway

End-to-examples

This directory contains an end-to-end flow for generating a gRPC API with HTTP transcoding from an OpenAPI description.

The tutorial uses the gRPC gateway plugin for the proxy.

End-to-end flow with gRPC gateway plugin

This example demonstrates an end-to-end flow for generating a gRPC API with HTTP transcoding from an OpenAPI description.

What we will build:

This tutorial has six steps:

1. Generate a gRPC service (.proto) from an OpenAPI description.
2. Generate server-side support code for the gRPC service.
3. Implement the server logic.
4. Set up a proxy that provides HTTP transcoding.
5. Run the proxy and the server.
6. Test your API with with curl and a gRPC client.

Prerequisite

Install gnostic, gnostic-grpc, go plugin for protoc, gRPC gateway plugin and gRPC

go get -u github.com/google/gnostic
go get -u github.com/google/gnostic-grpc
go get -u github.com/golang/protobuf/protoc-gen-go
go get -u github.com/grpc-ecosystem/grpc-gateway/protoc-gen-grpc-gateway
go get -u google.golang.org/grpc

For simplicity lets create a temporary environment variable inside your terminal:

export ANNOTATIONS="third-party/googleapis"

In order for this tutorial to work you should work inside this directory under GOPATH.

1. Step

Use gnostic to generate the Protocol buffer description (bookstore.proto) in the current directory:

gnostic --grpc-out=. bookstore.yaml

2. Step

Generate the gRPC stubs:

protoc --proto_path=. --proto_path=${ANNOTATIONS} --go_out=plugins=grpc:bookstore bookstore.proto

This generates bookstore/bookstore.pb.go.

3. Step

We added an example implementation of the server using the generated gRPC stubs inside bookstore/server.go.

4. Step

Generate the reverse proxy with the gRPC gateway plugin:

protoc --proto_path=. --proto_path=${ANNOTATIONS} --grpc-gateway_out=bookstore bookstore.proto

This generates bookstore/bookstore.pb.gw.go.

We provided a sample implementation on how to use the proxy inside bookstore/proxy.go.

5. Step

Start the proxy and the server:

go run main.go

6. Step

Inside of a new terminal test your API:

Let's create a shelf first:

curl -X POST \
  http://localhost:8081/shelves \
  -H 'Content-Type: application/json' \
  -d '{
    "name": "Books I need to read",
    "theme": "Non-fiction"
}'

Get all existing shelves:

curl -X GET http://localhost:8081/shelves

Create a book for the shelve with the id 1:

curl -X POST \
  http://localhost:8081/shelves/1/books \
  -H 'Content-Type: application/json' \
  -d '{
    "author": "Hans Rosling",
    "name": "Factfulness",
    "title": "Factfulness: Ten Reasons We'\''re wrong about the world - and Why Things Are Better Than You Think"
}'

List all books for the shelve with the id 1:

curl -X GET http://localhost:8081/shelves/1/books

A sample gRPC client is provided inside grpc-client/client.go that lists all themes of your shelves:

go run grpc-client/client.go