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gRPC

This example demonstrates how to route traffic to a gRPC service through the nginx controller.

Prerequisites

  1. You have a kubernetes cluster running.
  2. You have a domain name such as example.com that is configured to route traffic to the ingress controller.
  3. You have the nginx-ingress controller installed as per docs, with gRPC support.
  4. You have a backend application running a gRPC server and listening for TCP traffic. If you want, you can use https://github.com/grpc/grpc-go/blob/91e0aeb192456225adf27966d04ada4cf8599915/examples/features/reflection/server/main.go as an example.
  5. You're also responsible for provisioning an SSL certificate for the ingress. So you need to have a valid SSL certificate, deployed as a Kubernetes secret of type tls, in the same namespace as the gRPC application.

Step 1: Create a Kubernetes Deployment for gRPC app

  • Make sure your gRPC application pod is running and listening for connections. For example you can try a kubectl command like this below:
    $ kubectl get po -A -o wide | grep go-grpc-greeter-server
    
  • If you have a gRPC app deployed in your cluster, then skip further notes in this Step 1, and continue from Step 2 below.

  • As an example gRPC application, we can use this app https://github.com/grpc/grpc-go/blob/91e0aeb192456225adf27966d04ada4cf8599915/examples/features/reflection/server/main.go .

  • To create a container image for this app, you can use this Dockerfile.

  • If you use the Dockerfile mentioned above, to create a image, then given below is an example of a Kubernetes manifest, to create a deployment resource, that uses that image. If needed, then edit this manifest to suit your needs. Assuming the name of this yaml file is deployment.go-grpc-greeter-server.yaml ;

cat <<EOF | kubectl apply -f -
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: go-grpc-greeter-server
  name: go-grpc-greeter-server
spec:
  replicas: 1
  selector:
    matchLabels:
      app: go-grpc-greeter-server
  template:
    metadata:
      labels:
        app: go-grpc-greeter-server
    spec:
      containers:
      - image: <reponame>/go-grpc-greeter-server   # Edit this for your reponame
        resources:
          limits:
            cpu: 100m
            memory: 100Mi
          requests:
            cpu: 50m
            memory: 50Mi
        name: go-grpc-greeter-server
        ports:
        - containerPort: 50051
EOF

Step 2: Create the Kubernetes Service for the gRPC app

  • You can use the following example manifest to create a service of type ClusterIP. Edit the name/namespace/label/port to match your deployment/pod ;
    cat <<EOF | kubectl apply -f -
    apiVersion: v1
    kind: Service
    metadata:
      labels:
        app: go-grpc-greeter-server
      name: go-grpc-greeter-server
    spec:
      ports:
      - port: 80
        protocol: TCP
        targetPort: 50051
      selector:
        app: go-grpc-greeter-server
      type: ClusterIP
    EOF
    
  • You can save the above example manifest to a file with name service.go-grpc-greeter-server.yaml and edit it to match your deployment/pod, if required. You can create the service resource with a kubectl command like this ;
$ kubectl create -f service.go-grpc-greeter-server.yaml

Step 3: Create the Kubernetes Ingress resource for the gRPC app

  • Use the following example manifest of a ingress resource to create a ingress for your grpc app. If required, edit it to match your app's details like name, namespace, service, secret etc. Make sure you have the required SSL-Certificate, existing in your Kubernetes cluster, in the same namespace where the gRPC app is. The certificate must be available as a kubernetes secret resource, of type "kubernete.io/tls" https://kubernetes.io/docs/concepts/configuration/secret/#tls-secrets. This is because we are terminating TLS on the ingress;
cat <<EOF | kubectl apply -f -
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  annotations:
    kubernetes.io/ingress.class: "nginx"
    nginx.ingress.kubernetes.io/ssl-redirect: "true"
    nginx.ingress.kubernetes.io/backend-protocol: "GRPC"
  name: fortune-ingress
  namespace: default
spec:
  rules:
  - host: grpctest.dev.mydomain.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: go-grpc-greeter-server
            port:
              number: 80
  tls:
  # This secret must exist beforehand
  # The cert must also contain the subj-name grpctest.dev.mydomain.com
  # https://github.com/kubernetes/ingress-nginx/blob/master/docs/examples/PREREQUISITES.md#tls-certificates
  - secretName: wildcard.dev.mydomain.com
    hosts:
      - grpctest.dev.mydomain.com
EOF
  • If you save the above example manifest as a file named ingress.go-grpc-greeter-server.yaml and edit it to match your deployment and service, you can create the ingress like this ;
$ kubectl create -f ingress.go-grpc-greeter-server.yaml
  • The takeaway is that we are not doing any TLS configuration on the server (as we are terminating TLS at the ingress level, gRPC traffic will travel unencrypted inside the cluster and arrive "insecure").

  • For your own application you may or may not want to do this. If you prefer to forward encrypted traffic to your POD and terminate TLS at the gRPC server itself, add the ingress annotation nginx.ingress.kubernetes.io/backend-protocol: "GRPCS".

  • A few more things to note:

  • We've tagged the ingress with the annotation nginx.ingress.kubernetes.io/backend-protocol: "GRPC". This is the magic ingredient that sets up the appropriate nginx configuration to route http/2 traffic to our service.

  • We're terminating TLS at the ingress and have configured an SSL certificate wildcard.dev.mydomain.com. The ingress matches traffic arriving as https://grpctest.dev.mydomain.com:443 and routes unencrypted messages to the backend Kubernetes service.

Step 4: test the connection

  • Once we've applied our configuration to Kubernetes, it's time to test that we can actually talk to the backend. To do this, we'll use the grpcurl utility:
$ grpcurl grpctest.dev.mydomain.com:443 helloworld.Greeter/SayHello
{
  "message": "
}

Debugging Hints

  1. Obviously, watch the logs on your app.
  2. Watch the logs for the nginx-ingress-controller (increasing verbosity as needed).
  3. Double-check your address and ports.
  4. Set the GODEBUG=http2debug=2 environment variable to get detailed http/2 logging on the client and/or server.
  5. Study RFC 7540 (http/2) https://tools.ietf.org/html/rfc7540.

If you are developing public gRPC endpoints, check out https://proto.stack.build, a protocol buffer / gRPC build service that can use to help make it easier for your users to consume your API.

See also the specific GRPC settings of NGINX: https://nginx.org/en/docs/http/ngx_http_grpc_module.html

Notes on using response/request streams

  1. If your server does only response streaming and you expect a stream to be open longer than 60 seconds, you will have to change the grpc_read_timeout to accommodate for this.
  2. If your service does only request streaming and you expect a stream to be open longer than 60 seconds, you have to change the grpc_send_timeout and the client_body_timeout.
  3. If you do both response and request streaming with an open stream longer than 60 seconds, you have to change all three timeouts: grpc_read_timeout, grpc_send_timeout and client_body_timeout.

Values for the timeouts must be specified as e.g. "1200s".

On the most recent versions of nginx-ingress, changing these timeouts requires using the nginx.ingress.kubernetes.io/server-snippet annotation. There are plans for future releases to allow using the Kubernetes annotations to define each timeout separately.