CloudEvent Viewer

This micro-app can be used as a test subscriber and/or test emitter of CloudEvents.

It is very useful in an event-driven architecture in order to monitor events and test subscriptions.

Getting Started

Run two instances locally and send events between each other:

flowchart LR
    A((player:8080)) -->|emits|B((player:8081))
    B -->|emits|A

Loading

# http://localhost:8080
docker run -d --rm -it -p 8080:80 -e api_default_generator_gateways='{"urls": ["http://localhost/events/pub", "http://host.docker.internal:8080/events/pub", "http://host.docker.internal:8081/events/pub"]}' ghcr.io/bvandewe/events-player:latest

# http://localhost:8081
docker run -d --rm -it -p 8081:80 -e api_default_generator_gateways='{"urls": ["http://localhost/events/pub", "http://host.docker.internal:8080/events/pub", "http://host.docker.internal:8081/events/pub"]}' ghcr.io/bvandewe/events-player:latest

The app provides a web-based interface that enables users to visualize events as they are received on the POST /events/pub endpoint. The UI provides simple web-form that enables users to generate event(s) and emit/transmit them to a selected customizable event gateway.

It can very easily be deployed locally (included in a docker-compose file) or remotely (in Kubernetes or Docker) and may be configured as a subscriber to an event channel (like Cloud Streams).

Limitations

There is currently NO PERSISTANCE anywhere so refreshing the page on the browser will reset the state.
The frontend keeps a given amount of events as a rolling buffer with a configurable max-size (i.e. 1000 last events, older events are discarded).

Usage

The root URL shows a simple HTML page that automatically appends new CloudEvents as they are received by the backend (on the POST /events/pub endpoint) - and pops older events if the maximum stack size is reached.

• The UI stacks the events so that the most recent one is on top.
• User can search for any String anywhere in any events with the filter input box and the UI will show/hide events accordingly.
• User can toggle the display of the event details by clicking the any event header.
• There is a ToggleAll button next to the filter that will toggle the expand/collapse status of all events.

Deployment

The app backend validates and handles CloudEvents via the POST /events/pub endpoint and streams events to all currently connected clients/browsers via SSE.

• The payload must have the Content-Type header set to application/cloudevents+json.
• The event must be formatted as per the CloudEvents Specifications v1.0.2 in JSON Format.

When a valid event is received, a FastAPI background task simply pushes a copy of the event into the queue of each currently connected client/browser.

The SSE stream can be accessed at /stream using a browser or any SSE client. The stream sends a JSON payload for each received event, with the event payload and a timestamp indicating when the event was received.

Local Usage

1. Pull and run the Docker image:

   docker run --rm -it -p 8080:80 ghcr.io/bvandewe/cloudevents-player:latest

2. Browse to http://localhost:8080

3. Emit Cloudevent to http://localhost:8080/events/pub

4. Enjoy!

Development

Hint:

The debugger fails with vscode v1.75 (currently the latest version). Have to downgrade to 1.74: https://code.visualstudio.com/updates/v1_74 Then, disable automatic updates (settings > 'update': set to "none")