Knative Showcase

The apps in this repository are used to showcase basics of Knative Serving and Eventing. The same features are implemented both in Quarkus and Express.JS frameworks.

Features

The features below are there for two basic reasons. First reason is to showcase some of the features of the Knative (like scaling, traffic shaping, or event sending and receiving). The other group is to showcase some basic features almost every production ready application deployed on Kubernetes should have. The non-functional features were added, so the apps be close to the real world apps, and could serve as a reference for developers.

Knative related features

• Supports the PORT env

  PORT=3456
  # start the app... 
  http :$PORT

• /hello

  http :8080/hello

  Returns a hello JSON (sequenced), and sends Cloud Event to K_SINK target. A operational delay can be enforced by using DELAY (in msec) environmental variable.

• /events

  http :8080/events

  Returns a stream of Server-Sent Events, where each event is a CloudEvent represented in structured JSON format. This stream will continue to send next events if they come.

  kn event send --field a.b=true --to-url http://localhost:8080/events

  You can send events to the app, by POST /events endpoint. Those events will be stored in ephemeral im-memory storage and send to the listening clients.

Openshift Serverless related features

• / home page ready for Web, and CLI

  http :8080 user-agent:Mozilla/5.0
  # returns a React app when called from Browser,
  # together with browser for captured CloudEvents
  
  http :8080
  # returns a JSON with app's coordinates when called from command line

Supporting features

• K8s readyness and liveness probes

  http :8080/health/ready
  http :8080/health/live

• Prometeus metrics

  http :8080/metrics

• OpenAPI & Swagger UI

  http :8080/openapi.json
  http :8080/swagger-ui

• Input validation (validation by OpenAPI schema)

• Distributed Tracing

Architecture

We've prepared two backend implementations of the above feature. First one is implemented in Red Hat build of Quarkus framework and live in the quarkus directory. The second backend has been implemented in Express.JS, runs on Node, and lives in expressjs directory. Both of those backend are using single frontend, written in React framework, in Typescript.

├── quarkus/     # Quarkus backend
├── expressjs/   # Express.JS backend
├── frontend/    # React frontend
└── Makefile     # Main make file

The frontend application builds static Web files. They are packaged as Webjar in the user's Maven repository (~/.m2/repository). Thanks to that the Quarkus application is able to use those static files directly. The express backend needs to extract those webjar files.