traefik/docs/content/user-guides/grpc.md

gRPC Examples

With HTTP (h2c)

This section explains how to use Traefik as reverse proxy for gRPC application.

Traefik Configuration

## static configuration ##

[entryPoints]
  [entryPoints.http]
    address = ":80"

[api]
    
[providers.file]

## dynamic configuration ##

[http]

  [http.routers]
    [http.routers.routerTest]
      service = "srv-grpc"
      rule = "Host(`frontend.local`)"
    
  [http.services]
    [http.services.srv-grpc]
      [http.services.srv-grpc.loadBalancer]
        [[http.services.srv-grpc.loadBalancer.servers]]
          url = "h2c://backend.local:8080"

## static configuration ##

entryPoints:
  http:
    address: :80

providers:
  file: {}

api: {}

## dynamic configuration ##

http:
  routers:
    routerTest:
      service: srv-grpc
      rule: Host(`frontend.local`)

  services:
    srv-grpc:
      loadBalancer:
        servers:
        - url: h2c://backend.local:8080

!!! warning For providers with labels, you will have to specify the traefik.http.services.<my-service-name>.loadbalancer.server.scheme=h2c

Conclusion

We don't need specific configuration to use gRPC in Traefik, we just need to use h2c protocol, or use HTTPS communications to have HTTP2 with the backend.

With HTTPS

This section explains how to use Traefik as reverse proxy for gRPC application with self-signed certificates.

gRPC Server Certificate

In order to secure the gRPC server, we generate a self-signed certificate for service url:

openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout ./backend.key -out ./backend.cert

That will prompt for information, the important answer is:

Common Name (e.g. server FQDN or YOUR name) []: backend.local

gRPC Client Certificate

Generate your self-signed certificate for router url:

openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout ./frontend.key -out ./frontend.cert

with

Common Name (e.g. server FQDN or YOUR name) []: frontend.local

Traefik Configuration

At last, we configure our Traefik instance to use both self-signed certificates.

## static configuration ##

[entryPoints]
  [entryPoints.https]
    address = ":4443"


[serversTransport]
  # For secure connection on backend.local
  rootCAs = [ "./backend.cert" ]

[api]

[provider.file]

## dynamic configuration ##

[http]

  [http.routers]
    [http.routers.routerTest]
      service = "srv-grpc"
      rule = "Host(`frontend.local`)"
    
  [http.services]
    [http.services.srv-grpc]
      [http.services.srv-grpc.loadBalancer]
        [[http.services.srv-grpc.loadBalancer.servers]]
          # Access on backend with HTTPS
          url = "https://backend.local:8080"

[tls]

  # For secure connection on frontend.local
  [[tls.certificates]]
    certFile = "./frontend.cert"
    keyFile = "./frontend.key"

## static configuration ##

entryPoints:
  https:
    address: :4443

serversTransport:
  # For secure connection on backend.local
  rootCAs:
  - ./backend.cert

providers:
  file: {}

api: {}

## dynamic configuration ##

http:
  routers:
    routerTest:
      service: srv-grpc
      rule: Host(`frontend.local`)
  services:
    srv-grpc:
      loadBalancer:
        servers:
        # Access on backend with HTTPS
        - url: https://backend.local:8080
tls:
  # For secure connection on frontend.local
  certificates:
  - certfile: ./frontend.cert
    keyfile: ./frontend.key

!!! warning With some services, the server URLs use the IP, so you may need to configure insecureSkipVerify instead of the rootCAs to activate HTTPS without hostname verification.

A gRPC example in go (modify for https)

We use the gRPC greeter example in grpc-go

!!! warning In order to use this gRPC example, we need to modify it to use HTTPS

So we modify the "gRPC server example" to use our own self-signed certificate:

// ...

// Read cert and key file
backendCert, _ := ioutil.ReadFile("./backend.cert")
backendKey, _ := ioutil.ReadFile("./backend.key")

// Generate Certificate struct
cert, err := tls.X509KeyPair(backendCert, backendKey)
if err != nil {
  log.Fatalf("failed to parse certificate: %v", err)
}

// Create credentials
creds := credentials.NewServerTLSFromCert(&cert)

// Use Credentials in gRPC server options
serverOption := grpc.Creds(creds)
var s *grpc.Server = grpc.NewServer(serverOption)
defer s.Stop()

pb.RegisterGreeterServer(s, &server{})
err := s.Serve(lis)

// ...

Next we will modify gRPC Client to use our Traefik self-signed certificate:

// ...

// Read cert file
frontendCert, _ := ioutil.ReadFile("./frontend.cert")

// Create CertPool
roots := x509.NewCertPool()
roots.AppendCertsFromPEM(frontendCert)

// Create credentials
credsClient := credentials.NewClientTLSFromCert(roots, "")

// Dial with specific Transport (with credentials)
conn, err := grpc.Dial("frontend.local:4443", grpc.WithTransportCredentials(credsClient))
if err != nil {
    log.Fatalf("did not connect: %v", err)
}

defer conn.Close()
client := pb.NewGreeterClient(conn)

name := "World"
r, err := client.SayHello(context.Background(), &pb.HelloRequest{Name: name})

// ...