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Use the gRPC-Gateway plugin to proxy HTTP requests to a gRPC service

Uses: Kong Gateway deck
Deployment Platform
Related Documentation
Gateway Documentation decK Documentation
Tags
#transformations
Minimum Version
Kong Gateway - 3.4
TL;DR

Create a Gateway Service with the grpc protocol, then create a Route and enable the gRPC-Gateway plugin. Specify the path to your Protobuf file in the config.proto parameter.

Prerequisites

Kong Konnect

This is a Konnect tutorial and requires a Konnect personal access token.

  1. Create a new personal access token by opening the Konnect PAT page and selecting Generate Token.

  2. Export your token to an environment variable:

     export KONNECT_TOKEN='YOUR_KONNECT_PAT'

  3. Run the quickstart script to automatically provision a Control Plane and Data Plane, and configure your environment:

     curl -Ls https://get.konghq.com/quickstart | bash -s -- -k $KONNECT_TOKEN --deck-output

    This sets up a Konnect Control Plane named quickstart, provisions a local Data Plane, and prints out the following environment variable exports:

     export DECK_KONNECT_TOKEN=$KONNECT_TOKEN
 export DECK_KONNECT_CONTROL_PLANE_NAME=quickstart
 export KONNECT_CONTROL_PLANE_URL=https://us.api.konghq.com
 export KONNECT_PROXY_URL='http://localhost:8000'

    Copy and paste these into your terminal to configure your session.

Kong Gateway running

This tutorial requires Kong Gateway Enterprise. If you don’t have Kong Gateway set up yet, you can use the quickstart script with an enterprise license to get an instance of Kong Gateway running almost instantly.

  1. Export your license to an environment variable:

     export KONG_LICENSE_DATA='LICENSE-CONTENTS-GO-HERE'

  2. Run the quickstart script:

    curl -Ls https://get.konghq.com/quickstart | bash -s -- -e KONG_LICENSE_DATA

    Once Kong Gateway is ready, you will see the following message:

     Kong Gateway Ready

decK   v1.43+

decK is a CLI tool for managing Kong Gateway declaratively with state files. To complete this tutorial, install decK version 1.43 or later.

This guide uses deck gateway apply, which directly applies entity configuration to your Gateway instance. We recommend upgrading your decK installation to take advantage of this tool.

You can check your current decK version with deck version.

Create a Protobuf definition

Use the following command to create a sample Protobuf definition:

echo 'syntax = "proto3";

package hello;

service HelloService {
 rpc SayHello(HelloRequest) returns (HelloResponse) {
   option (google.api.http) = {
     get: "/v1/messages/{name}"
     additional_bindings {
       get: "/v1/messages/legacy/{name=**}"
     }
     post: "/v1/messages/"
     body: "*"
   };
 }
}


// The request message containing the name.
message HelloRequest {
 string name = 1;
}

// The response message containing the greeting
message HelloResponse {
 string message = 1;
}' > hello-gateway.proto

This sample definition modifies the SayHello method available on grpcb.in and will return a message containing “Hello” followed by a name that can be specified either in the URL for GET requests or in the request body for POST requests.

Add the Protobuf definition to your Docker container

Since Konnect data plane container names can vary, set your container name as an environment variable:

export KONNECT_DP_CONTAINER='your-dp-container-name'

Use the following command to add hello-gateway.proto to the /usr/local/kong directory in your Kong Gateway Docker container:

docker cp hello-gateway.proto kong-quickstart-gateway:/usr/local/kong

docker cp hello-gateway.proto $KONNECT_DP_CONTAINER:/usr/local/kong

Create a Gateway Service and a Route

In this example, we want a Route that serves the HTTP protocol but proxies to a Gateway Service with the gRPC protocol. For testing purposes, we’ll use grpcb.in as the upstream service.

echo '
_format_version: "3.0"
services:
  - name: example-grpc-service
    protocol: grpc
    host: grpcb.in
    port: 9000
routes:
  - name: http-route
    protocols:
    - http
    paths:
    - "/"
    service:
      name: example-grpc-service
' | deck gateway apply -

Enable the gRPC-Gateway plugin

Configure the plugin to use the Protobuf definition we created:

echo '
_format_version: "3.0"
plugins:
  - name: grpc-gateway
    route: http-route
    config:
      proto: "/usr/local/kong/hello-gateway.proto"
' | deck gateway apply -

Validate

To validate that the configuration is working as expected, you can:

  • Send a GET request to /v1/messages/ or /v1/messages/legacy/, with a name in the URL:
curl "$KONNECT_PROXY_URL/v1/messages/MyName" \
     --no-progress-meter --fail-with-body 

curl "http://localhost:8000/v1/messages/MyName" \
     --no-progress-meter --fail-with-body
  • Send a POST request to /v1/messages/ with a name in the request body:
curl -X POST "$KONNECT_PROXY_URL/v1/messages/" \
     --no-progress-meter --fail-with-body  \
     --json '{
       "name": "MyName"
     }'

curl -X POST "http://localhost:8000/v1/messages/" \
     --no-progress-meter --fail-with-body  \
     --json '{
       "name": "MyName"
     }'

Cleanup

Clean up Konnect environment

If you created a new control plane and want to conserve your free trial credits or avoid unnecessary charges, delete the new control plane used in this tutorial.

Destroy the Kong Gateway container

 
curl -Ls https://get.konghq.com/quickstart | bash -s -- -d
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