Using HTTP2 and gRPC - Serving | Serverless | OpenShift Container Platform 4.9

OpenShift Serverless supports only insecure or edge-terminated routes. Insecure or edge-terminated routes do not support HTTP2 on OpenShift Container Platform. These routes also do not support gRPC because gRPC is transported by HTTP2. If you use these protocols in your application, you must call the application using the ingress gateway directly. To do this you must find the ingress gateway’s public address and the application’s specific host.

Interacting with a serverless application using HTTP2 and gRPC

This method applies to OpenShift Container Platform 4.10 and later. For older versions, see the following section.

Prerequisites

Install OpenShift Serverless Operator and Knative Serving on your cluster.
Install the OpenShift CLI (oc).
Create a Knative service.
Upgrade OpenShift Container Platform 4.10 or later.
Enable HTTP/2 on OpenShift Ingress controller.

Procedure

Add the serverless.openshift.io/default-enable-http2=true annotation to the KnativeServing Custom Resource:

$ oc annotate knativeserving <your_knative_CR> -n knative-serving serverless.openshift.io/default-enable-http2=true

After the annotation is added, you can verify that the appProtocol value of the Kourier service is h2c:
```
$ oc get svc -n knative-serving-ingress kourier -o jsonpath="{.spec.ports[0].appProtocol}"
```
Example output
```
h2c
```

Now you can use the gRPC framework over the HTTP/2 protocol for external traffic, for example:

import "google.golang.org/grpc"

grpc.Dial(
   YOUR_URL, (1)
   grpc.WithTransportCredentials(insecure.NewCredentials())), (2)
)

1	Your `ksvc` URL.
2	Your certificate.

Additional resources

Enabling HTTP/2 Ingress connectivity

Interacting with a serverless application using HTTP2 and gRPC in OpenShift Container Platform 4.9 and older

This method needs to expose Kourier Gateway using the LoadBalancer service type. You can configure this by adding the following YAML to your KnativeServing custom resource definition (CRD):

...
spec:
  ingress:
    kourier:
      service-type: LoadBalancer
...

Prerequisites

Install OpenShift Serverless Operator and Knative Serving on your cluster.
Install the OpenShift CLI (oc).
Create a Knative service.

Procedure

Find the application host. See the instructions in Verifying your serverless application deployment.

Find the ingress gateway’s public address:

$ oc -n knative-serving-ingress get svc kourier

Example output

NAME                   TYPE           CLUSTER-IP      EXTERNAL-IP                                                             PORT(S)                                                                                                                                      AGE
kourier   LoadBalancer   172.30.51.103   a83e86291bcdd11e993af02b7a65e514-33544245.us-east-1.elb.amazonaws.com   80:31380/TCP,443:31390/TCP   67m

The public address is surfaced in the EXTERNAL-IP field, and in this case is a83e86291bcdd11e993af02b7a65e514-33544245.us-east-1.elb.amazonaws.com.

Manually set the host header of your HTTP request to the application’s host, but direct the request itself against the public address of the ingress gateway.

$ curl -H "Host: hello-default.example.com" a83e86291bcdd11e993af02b7a65e514-33544245.us-east-1.elb.amazonaws.com

Example output

Hello Serverless!

You can also make a direct gRPC request against the ingress gateway:

import "google.golang.org/grpc"

grpc.Dial(
    "a83e86291bcdd11e993af02b7a65e514-33544245.us-east-1.elb.amazonaws.com:80",
    grpc.WithAuthority("hello-default.example.com:80"),
    grpc.WithInsecure(),
)

Ensure that you append the respective port, 80 by default, to both hosts as shown in the previous example.