Transcoding gRPC to HTTP/JSON

Sample project showing how to expose a gRPC service as a HTTP/JSON api.

There is a blogpost containing an in-depth explanation of this project

Transcoding gRPC to HTTP JSON using Envoy

Built with Java 11, but 1.8 should also be supported, change sourceCompatibility in the build.gradle to 1.8

Requirements: docker

Getting started

Open the project in your favourite IDE
- run ./gradlew idea or ./gradlew eclipse to configure your IDE to detect the generated code directories.
Run ./gradlew build on Linux/Mac, or gradlew.bat build on Windows to run a build.
Run ServerMain to start the gRPC server!
Run ClientMain to test some calls using the generated gRPC client
follow the steps below

If you want to Run ./gradlew generateProto generates sources from your .proto files

exposing the gRPC service as HTTP/JSON using Envoy proxy

Requirements:

protoc (to generate a service definition that envoy understands)
docker (envoy comes in a docker container)

Installing protoc

Goto: https://github.com/protocolbuffers/protobuf/releases/latest" +

download choose the precompiled version " +

for linux:   protoc-3.6.1-linux-x86_64.zip" +
for windows: protoc-3.6.1-win32.zip" +
for mac:     protoc-3.6.1-osx-x86_64.zip" +

extract it somewhere in your PATH

Installing docker

Check out this page: Install docker

Running Envoy to transcode our service

The script start-envoy.sh automates the tasks below for linux and mac:

./start-envoy.sh

Manual steps if script does not work

Run the protoc command from within this project's root directory! notice that build/extracted-include-protos/main contains proto files from jar files on the classpath, for example: com.google.api.grpc:googleapis-common-protos:0.0.3 this dependency contains the sources for google.api.http options we use in the .proto file
```
protoc -I. -Ibuild/extracted-include-protos/main --include_imports --include_source_info --descriptor_set_out=reservation_service_definition.pb src/main/proto/reservation_service.proto
```

Run envoy (docker container) from within this directory

docker run -it --rm --name envoy --network="host" -v "$(pwd)/reservation_service_definition.pb:/tmp/reservation_service_definition.pb:ro" -v "$(pwd)/envoy-config.yml:/etc/envoy/envoy.yaml:ro" envoyproxy/envoy

Testing the REST API

Create a reservation

 curl -X POST \
   http://localhost:51051/v1/reservations \
   -H 'Content-Type: application/json' \
   -d '{
     "title": "Lunchmeeting2",
     "venue": "JDriven Coltbaan 3",
     "room": "atrium",
     "timestamp": "2018-10-10T11:12:13",
     "attendees": [
         {
             "ssn": "1234567890",
             "firstName": "Jimmy",
             "lastName": "Jones"
         },
         {
             "ssn": "9999999999",
             "firstName": "Dennis",
             "lastName": "Richie"
         }
     ]
 }'

Example output:

 {
     "id": "2cec91a7-d2d6-4600-8cc3-4ebf5417ac4b",
     "title": "Lunchmeeting2",
     "venue": "JDriven Coltbaan 3",
     "room": "atrium",
     "timestamp": "2018-10-10T11:12:13",
     "attendees": [
         {
             "ssn": "1234567890",
             "firstName": "Jimmy",
             "lastName": "Jones"
         },
         {
             "ssn": "9999999999",
             "firstName": "Dennis",
             "lastName": "Richie"
         }
     ]
 }

Retrieve it (substitute ID in url):

curl -X GET http://localhost:51051/v1/reservations/<enter-id!!>

example output

{
    "id": "2cec91a7-d2d6-4600-8cc3-4ebf5417ac4b",
    "title": "Lunchmeeting2",
    "venue": "JDriven Coltbaan 3",
    "room": "atrium",
    "timestamp": "2018-10-10T11:12:13",
    "attendees": [
        {
            "ssn": "1234567890",
            "firstName": "Jimmy",
            "lastName": "Jones"
        },
        {
            "ssn": "9999999999",
            "firstName": "Dennis",
            "lastName": "Richie"
        }
    ]
}

Delete it (substitute ID in url):

curl -X DELETE http://localhost:51051/v1/reservations/<enter-id!!>

Create several reservations (vary the fields), and then list them with
```
curl -X GET http://localhost:51051/v1/reservations
```

Then list them with a search on venue only

curl -X GET "http://localhost:51051/v1/reservations?venue=JDriven%20Coltbaan%203"

example output:

[
    {
        "id": "2cec91a7-d2d6-4600-8cc3-4ebf5417ac4b",
        "title": "Lunchmeeting2",
        "venue": "JDriven Coltbaan 3",
        "room": "atrium",
        "timestamp": "2018-10-10T11:12:13",
        "attendees": [
            {
                "ssn": "1234567890",
                "firstName": "Jimmy",
                "lastName": "Jones"
            },
            {
                "ssn": "9999999999",
                "firstName": "Dennis",
                "lastName": "Richie"
            }
        ]
    },
    {
        "id": "2f23c05a-c0ed-4b60-9b21-479d640030cc",
        "title": "Lunchmeeting",
        "venue": "JDriven Coltbaan 3",
        "timestamp": "2018-10-10T11:12:13",
        "attendees": [
            {
                "ssn": "1234567890",
                "firstName": "Jimmy",
                "lastName": "Jones"
            },
            {
                "ssn": "9999999999",
                "firstName": "Dennis",
                "lastName": "Richie"
            }
        ]
    }
]

ianomad/transcoding-grpc-to-http-json