sse.kafka.fanout

Listens on http port 7114 or https port 7114 and will stream back whatever is published to the events topic in Kafka.

Requirements

• docker compose
• sse-cat

Install sse-cat client

Requires Server-Sent Events client, such as sse-cat version 2.0.5 or higher on node version 14 or higher.

npm install -g sse-cat

Setup

To start the Docker Compose stack defined in the compose.yaml file, use:

docker compose up -d

Verify behavior

Open a text/event-stream from the sse endpoint in a terminal.

curl -N --http2 -H "Accept:text/event-stream" "http://localhost:7114/events"

In a new terminal send a text payload from the kafkacat producer client.

echo '{ "id": 1, "name": "Hello World!"}' | docker compose -p zilla-sse-kafka-fanout exec -T kafkacat \
  kafkacat -P -b kafka.examples.dev:29092 -t events -k "1"

The text payload will be the data: of the sse message seen in the text/event-stream terminal session.

Note that only the latest messages with distinct keys are guaranteed to be retained by a compacted Kafka topic, so use different values for -k above to retain more than one message in the events topic.

Browser

Browse to http://localhost:7114/index.html and make sure to visit the localhost site and trust the localhost certificate.

Click the Go button to attach the browser SSE event source to Kafka via Zilla.

All non-compacted messages with distinct keys in the events Kafka topic are replayed to the browser.

Open the browser developer tools console to see additional logging, such as the open event.

Additional messages produced to the events Kafka topic then arrive at the browser live.

Reliability

Simulate connection loss by stopping the zilla service in the docker stack.

docker compose -p zilla-sse-kafka-fanout stop zilla

This causes errors to be logged in the browser console during repeated attempts to automatically reconnect.

Simulate connection recovery by starting the zilla service again.

docker compose -p zilla-sse-kafka-fanout start zilla

Any messages produced to the events Kafka topic while the browser was attempting to reconnect are now delivered immediately.

Additional messages produced to the events Kafka topic then arrive at the browser live.

Teardown

To remove any resources created by the Docker Compose stack, use:

docker compose down