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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 requests with the following protocols:

  • http
  • https

This plugin is compatible with DB-less mode.

In DB-less mode, Kong Gateway does not have an Admin API. If using this mode, configure the plugin using declarative configuration.

Enabling the plugin on a route

Admin API
Kubernetes
Declarative (YAML)
Konnect SaaS
Manager

For example, configure this plugin on a route with:

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$ curl -X POST http://<admin-hostname>:8001/routes/<route>/plugins \
    --data "name=grpc-gateway"  \
    --data "config.proto=path/to/hello.proto"

<route> is the id or name of the route that this plugin configuration will target.

First, create a KongPlugin resource:

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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:

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apiVersion: networking/v1beta1
kind: Ingress
metadata:
  name: <route>
  annotations:
    kubernetes.io/ingress.class: kong
    konghq.com/plugins: <grpc-gateway-example>
spec:
  rules:
  - host: examplehostname.com
    http:
      paths:
      - path: /bar
        backend:
          serviceName: echo
          servicePort: 80

<route> is 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.

For example, configure this plugin on a route by adding this section to your declarative configuration file:

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

<route> is the id or name of the route that this plugin configuration will target.

Configure this plugin on a route:

  1. In Konnect SaaS, select the service from the ServiceHub page.
  2. Scroll down to Versions and select the version.
  3. Select the route.
  4. Scroll down to Plugins and click Add Plugin.
  5. Find and select the gRPC-gateway plugin.
  6. Click Create.

Configure this plugin on a route:

  1. In Kong Manager, select the workspace.
  2. From the Dashboard, select Routes in the left navigation.
  3. Click View for the route row.
  4. Scroll down to plugins and click Add Plugin.

  5. Find and select the gRPC-gateway plugin.

    Note: If the plugin is greyed out, then it is not available for your product tier. See Kong Gateway tiers.
  6. If the option is available, select Scoped.
  7. Add the Route ID if it is not already prefilled.
  8. Click Create.

Enabling the plugin globally

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.

Admin API
Kubernetes
Declarative (YAML)
Kong Manager

For example, configure this plugin globally with:

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$ curl -X POST http://<admin-hostname>:8001/plugins/ \
    --data "name=grpc-gateway"  \
    --data "config.proto=path/to/hello.proto"

Create a KongClusterPlugin resource and label it as global:

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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

For example, configure this plugin using the plugins: entry in the declarative configuration file:

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

Configure this plugin globally:

  1. In Kong Manager, select the workspace.
  2. From the Dashboard, select Plugins in the left navigation.
  3. Click New Plugin.

  4. Find and select the gRPC-gateway plugin.

    Note: If the plugin is greyed out, then it is not available for your product tier. See Kong Gateway tiers.
  5. If the option is available, set the plugin scope to Global.
  6. Click Create.

Parameters

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

Form ParameterDescription
name

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

Type: string		 The ID of the Route the plugin targets.
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):

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_format_version: "1.1"
services:
- protocol: grpc
  host: localhost
  port: 9000
  routes:
  - protocols:
    - http
    paths:
    - /
    plugins:
    - name: grpc-gateway
      config:
        proto: path/to/hello.proto

Sample configuration via the Admin API:

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$ # add the gRPC service
$ curl -XPOST localhost:8001/services \
  --data name=grpc \
  --data protocol=grpc \
  --data host=localhost \
  --data port=9000

$ # add an http route
$ curl -XPOST localhost:8001/services/grpc/routes \
  --data protocols=http \
  --data name=web-service \
  --data paths[]=/

$ # add the plugin to the route
$ curl -XPOST 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:

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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 HelloReply {
  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:

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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.

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

See also

Introduction to Kong gRPC plugins