How to call grpc service in openshift from java

Question

I have a client and a service with gRPC. Locally they work well. I tried to start the server in openshift (minishift):

kind: DeploymentConfig
    apiVersion: v1
    metadata:
      name: app-grpc
    spec:
      replicas: 1
      selector:
        app: app-grpc
      template:
        metadata:
          labels:
            app: app-grpc
        spec:
          containers:
            - name: app-grpc
              ports:
                - containerPort: 9005
                  protocol: TCP
              imagePullPolicy: Always
          restartPolicy: Always
          dnsPolicy: ClusterFirst

---
kind: Service
apiVersion: "v1"
metadata:
  name: "app-grpc-service"
spec:
  ports:
    - port: 9005
      targetPort: 9005
  selector:
    app: "app-grpc"

---
kind: Route
apiVersion: route.openshift.io/v1
metadata:
  name: "app-grpc-route"
spec:
  to:
    kind: Service
    name: app-grpc-service

But the call from the client does not reach the server. I am not sure if I have configured Service and Route correctly

The client looks like this:

ManagedChannel channel = NettyChannelBuilder
    .forAddress("app-grpc-route-myproject.111.111.111.111.nip.io/app-grpc", 9005)
    .usePlaintext()
    .build();

try {
    HelloServiceGrpc.HelloServiceBlockingStub client = HelloServiceGrpc.newBlockingStub(channel);
    System.out.println(client.hello(HelloRequest.newBuilder()
        .setFirstName("firstName")
        .setLastName("lastName")
        .build())
        .getGreeting());
} catch (InterruptedException e) {
    e.printStackTrace();
} finally {
    channel.shutdown();
}

I'm not sure if I'm specifying host correctly. I copied it from route.

When trying to call forAddress("app-grpc-route-myproject.111.111.111.111.nip.io", 9005)I have Caused by: io.netty.channel.AbstractChannel$AnnotatedConnectException: Connection refused: no further information

If I use .forAddress("app-grpc-route-myproject.111.111.111.111.nip.io/app-grpc", 9005) I have Caused by: io.netty.handler.codec.http2.Http2Exception: First received frame was not SETTINGS. Hex dump for first 5 bytes: 485454502f

Answer 1

To be able to serve gRPC connections, you need your ingress controller to handle HTTP2 connections.

This is not the case by default.

So, your answer might be to enter the following command:

oc annotate ingresses.config/cluster ingress.operator.openshift.io/default-enable-http2=true