Deploy WebSocket and gRPC Services on Knative: A Step‑by‑Step Guide

Overview

Knative Serving can run both WebSocket and gRPC workloads without additional Istio configuration. The article provides two minimal Go examples—one for a WebSocket chat service and one for a gRPC ping service—together with Docker images and Knative Service definitions.

WebSocket Example

The source code (including vendor dependencies, Dockerfile, Makefile and service.yaml) is available at https://github.com/knative-sample/websocket-chat. A pre‑built image can be pulled from

registry.cn-hangzhou.aliyuncs.com/knative-sample/websocket-chat:2019-10-15

. Deploy the service with: kubectl apply -f service.yaml Typical service.yaml:

apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: websocket-chat
spec:
  template:
    spec:
      containers:
      - image: registry.cn-hangzhou.aliyuncs.com/knative-sample/websocket-chat:2019-10-15
        ports:
        - name: http1
          containerPort: 8080

After deployment, retrieve the service URL with kubectl get ksvc and open it in a browser. Using two browser windows—one to send messages and the other to receive—verifies that the WebSocket upgrade works correctly.

gRPC Example

The complete code and a ready‑to‑use image are hosted at https://github.com/knative-sample/grpc-ping-go. The image can be pulled from

registry.cn-hangzhou.aliyuncs.com/knative-sample/grpc-ping-go:2019-10-15

. Deploy the service using its service.yaml: kubectl apply -f service.yaml Typical service.yaml for the gRPC server:

apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: grpc-ping
spec:
  template:
    spec:
      containers:
      - image: registry.cn-hangzhou.aliyuncs.com/knative-sample/grpc-ping-go:2019-10-15
        ports:
        - name: h2c
          containerPort: 8080

Obtain the service URL with kubectl get ksvc (e.g., grpc-ping.default.serverless.kuberun.com). Test the service by running the client container:

docker run --rm registry.cn-hangzhou.aliyuncs.com/knative-sample/grpc-ping-go:2019-10-15 \
  /client -server_addr="grpc-ping.default.serverless.kuberun.com:80" -insecure

The client prints repeated lines such as “Ping got hello – pong”, confirming successful gRPC (h2c) communication through Knative.

Key Points

Knative Serving automatically handles WebSocket upgrades and HTTP/2 cleartext (h2c) for gRPC without extra Istio settings.

Typical workflow: clone the repository, build or pull the Docker image, apply the Knative Service YAML, and verify the endpoint with kubectl get ksvc and appropriate client tools.