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gRPC-gateway

A Kong plugin to allow access to a gRPC service via HTTP REST requests and translate requests and responses in a JSON format. Similar to gRPC-gateway.

Configuration Reference

This plugin is compatible with DB-less mode.

In DB-less mode, you configure Kong Gateway declaratively. Therefore, the Admin API is mostly read-only. The only tasks it can perform are all related to handling the declarative config, including:

  • Setting a target's health status in the load balancer
  • Validating configurations against schemas
  • Uploading the declarative configuration using the /config endpoint

Example plugin configuration

The following examples provide some typical configurations for enabling the grpc-gateway plugin on a route.

Make the following request:

curl -X POST http://localhost:8001/routes/ROUTE_NAME|ROUTE_ID/plugins \
  --data "name=grpc-gateway"  \
    --data "config.proto=path/to/hello.proto"

Replace ROUTE_NAME|ROUTE_ID with the id or name of the route that this plugin configuration will target.

First, create a KongPlugin resource:

apiVersion: configuration.konghq.com/v1
kind: KongPlugin
metadata:
  name: grpc-gateway-example
config: 
  proto: path/to/hello.proto
plugin: grpc-gateway

Then, apply it to an ingress (route or routes) by annotating the ingress as follows:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: ROUTE_NAME|ROUTE_ID
  annotations:
    kubernetes.io/ingress.class: kong
    konghq.com/plugins: grpc-gateway-example
spec:
  rules:
  - host: examplehostname.com
    http:
      paths:
      - path: /bar
        backend:
          service:
            name: echo
            port:
              number: 80

Replace ROUTE_NAME|ROUTE_ID with the id or name of the route that this plugin configuration will target.

Note: The KongPlugin resource only needs to be defined once and can be applied to any service, consumer, or route in the namespace. If you want the plugin to be available cluster-wide, create the resource as a KongClusterPlugin instead of KongPlugin.

Add this section to your declarative configuration file:

plugins:
- name: grpc-gateway
  route: ROUTE_NAME
  config: 
    proto: path/to/hello.proto

Replace ROUTE_NAME|ROUTE_ID with the id or name of the route that this plugin configuration will target.

You can configure this plugin through the Konnect UI.

From the servicehub icon Service Hub, select a service version, then set up the plugin:

  1. Select a route.
  2. In the Plugins section, click Add Plugin.
  3. Find and select the gRPC-gateway plugin.
  4. Click Create.

You can configure this plugin through the Kong Manager UI.

  1. In Kong Manager, select the workspace.
  2. Open Routes from the menu, then click View for the route row.
  3. From the plugin section, click Add Plugin.
  4. Find and select the gRPC-gateway plugin.
  5. If the option is available, select Scoped.
  6. Add the route ID if it is not already prefilled.
  7. Click Create.

A plugin which is not associated to any service, route, or consumer is considered global, and will be run on every request. Read the Plugin Reference and the Plugin Precedence sections for more information.

The following examples provide some typical configurations for enabling the grpc-gateway plugin globally.

Make the following request:

curl -X POST http://localhost:8001/plugins/ \
  --data "name=grpc-gateway"  \
    --data "config.proto=path/to/hello.proto"

Create a KongClusterPlugin resource and label it as global:

apiVersion: configuration.konghq.com/v1
kind: KongClusterPlugin
metadata:
  name: <global-grpc-gateway>
  annotations:
    kubernetes.io/ingress.class: kong
  labels:
    global: \"true\"
config: 
  proto: path/to/hello.proto
plugin: grpc-gateway

Add a plugins entry in the declarative configuration file:

plugins:
- name: grpc-gateway
  config: 
    proto: path/to/hello.proto

You can configure this plugin through the Kong Manager UI.

  1. In Kong Manager, select the workspace.
  2. Open Plugins from the menu, then click New Plugin.
  3. Find and select the gRPC-gateway plugin.
  4. If the option is available, set the plugin scope to Global.
  5. Click Create.

Parameters

Here's a list of all the parameters which can be used in this plugin's configuration:

Form Parameter Description
name
required

Type: string		 The name of the plugin, in this case grpc-gateway.
route.name or route.id

Type: string		 The name or ID of the route the plugin targets.

Set one of these parameters if adding the plugin to a route through the top-level /plugins endpoint.

Not required if using /routes/ROUTE_NAME|ROUTE_ID/plugins.
enabled

Type: boolean

Default value: true		 Whether this plugin will be applied.
config.proto
optional

Type: string

Describes the gRPC types and methods. HTTP configuration must be defined in the file.

Purpose

This plugin translates requests and responses between gRPC and HTTP REST.

grpc-gateway

Image credit: grpc-gateway

Usage

This plugin should be enabled on a Kong Route that serves the http(s) protocol but proxies to a Service with the grpc(s) protocol.

Sample configuration via declarative (YAML):

_format_version: "3.0"
services:
- protocol: grpc
  host: localhost
  port: 9000
  routes:
  - protocols:
    - name: http
    paths:
    - /
    plugins:
    - name: grpc-gateway
      config:
        proto: path/to/hello.proto

Sample configuration via the Admin API:

  1. Add the gRPC service: 
      curl -X POST localhost:8001/services \
 --data name=grpc \
 --data protocol=grpc \
 --data host=localhost \
 --data port=9000
  2. Add an http route: 
      curl -X POST localhost:8001/services/grpc/routes \
 --data protocols=http \
 --data name=web-service \
 --data paths[]=/
  3. Add the plugin to the route: 
      curl -X POST localhost:8001/routes/web-service/plugins \
 --data name=grpc-gateway

The proto file must contain the HTTP REST to gRPC mapping rule.

The example uses the following mapping:

syntax = "proto2";

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 user's name.
message HelloRequest {
  string name = 1;
}

// The response message containing the greetings
message HelloResponse {
  string message = 1;
}

Note the option (google.api.http) = {} section is required.

You can send the following requests to Kong that translate to the corresponding gRPC requests:

curl -XGET localhost:8000/v1/messages/Kong2.0
{"message":"Hello Kong2.0"}

curl -XGET localhost:8000/v1/messages/legacy/Kong2.0
{"message":"Hello Kong2.0"}

curl -XGET localhost:8000/v1/messages/legacy/Kong2.0/more/paths
{"message":"Hello Kong2.0\/more\/paths"}

curl -XPOST localhost:8000/v1/messages/Kong2.0 -d '{"name":"kong2.0"}'
{"message":"Hello kong2.0"}

All syntax defined in Path template syntax is supported.

Object fields not mentioned in the endpoint paths as in /messages/{name} can be passed as URL arguments, for example /v1/messages?name=Kong. Structured arguments are supported.

For example, a request like the following:

/v1/messages?dest.name=Freddy&dest.address=1428+Elm+Street&message=One+Two...

is interpreted like the following JSON object:

{
  "dest": {
    "name": "Freddy",
    "address": "1428 Elm Street"
  },
  "message": "One Two..."
}

Similarly, fields of the type google.protobuf.Timestamp are converted to and from strings in ISO8601 format.

Currently only unary requests are supported; streaming requests are not supported.

See also

Introduction to Kong gRPC plugins

Changelog

Kong Gateway 2.6.x

  • Fields of type .google.protobuf.Timestamp on the gRPC side are now transcoded to and from ISO8601 strings on the REST side.
  • URI arguments like ..?foo.bar=x&foo.baz=y are interpreted as structured fields, equivalent to {"foo": {"bar": "x", "baz": "y"}}.