# gRPC examples
## With HTTP (h2c)
This section explains how to use Traefik as reverse proxy for gRPC application.
### Træfik configuration
At last, we configure our Træfik instance to use both self-signed certificates.
```toml
defaultEntryPoints = ["https"]
[entryPoints]
[entryPoints.http]
address = ":80"
[entryPoints.http]
[api]
[file]
[backends]
[backends.backend1]
[backends.backend1.servers.server1]
# Access on backend with h2c
url = "h2c://backend.local:8080"
[frontends]
[frontends.frontend1]
backend = "backend1"
[frontends.frontend1.routes.test_1]
rule = "Host:frontend.local"
```
!!! warning
For provider with label, you will have to specify the `traefik.protocol=h2c`
### Conclusion
We don't need specific configuration to use gRPC in Træfik, 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 backend url:
```bash
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 frontend url:
```bash
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
```
### Træfik configuration
At last, we configure our Træfik instance to use both self-signed certificates.
```toml
defaultEntryPoints = ["https"]
# For secure connection on backend.local
rootCAs = [ "./backend.cert" ]
[entryPoints]
[entryPoints.https]
address = ":4443"
[entryPoints.https.tls]
# For secure connection on frontend.local
[[entryPoints.https.tls.certificates]]
certFile = "./frontend.cert"
keyFile = "./frontend.key"
[api]
[file]
[backends]
[backends.backend1]
[backends.backend1.servers.server1]
# Access on backend with HTTPS
url = "https://backend.local:8080"
[frontends]
[frontends.frontend1]
backend = "backend1"
[frontends.frontend1.routes.test_1]
rule = "Host:frontend.local"
```
!!! warning
With some backends, 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](https://github.com/grpc/grpc-go/tree/master/examples/helloworld)
!!! 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:
```go
// ...
// 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 Træfik self-signed certificate:
```go
// ...
// 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})
// ...
```