Kafka SSE Example

This example project reads messages from a Kafka service and exposes the data over an HTTP streaming API using Server-Sent Events (SSE) protocol. It is written using Python & Django, and relies on Pushpin for managing the streaming connections.

Setup and use

Setup virtualenv and install dependencies:

virtualenv --python=python3 venv
. venv/bin/activate
pip install -r requirements.txt

Create a suitable .env with Kafka and Pushpin settings:

KAFKA_CONSUMER_CONFIG={"bootstrap.servers":"localhost:9092","group.id":"mygroup"}
GRIP_URL=http://localhost:5561

Run the Django server:

python manage.py runserver

Run Pushpin:

pushpin --route="* localhost:8000"

Run the relay command:

python manage.py relay

The relay command sets up a Kafka consumer according to KAFKA_CONSUMER_CONFIG, subscribes to all topics, and re-publishes received messages to Pushpin, wrapped in SSE format.

Clients can listen to events by making a request (through Pushpin) to /events/{topic}/:

curl -i http://localhost:7999/events/test/

The output stream might look like this:

HTTP/1.1 200 OK
Content-Type: text/event-stream
Transfer-Encoding: chunked
Connection: Transfer-Encoding

event: message
data: hello

event: message
data: world

How it works

The code is relatively simple. views.py sets up the SSE endpoint and relay.py does the message I/O.

Limitations

This is a simple example project. In a real project you'd want to consider:

• Authenticating clients
• Only subscribing to Kafka topics for which there are listening clients