Simple Async Pub/Sub

This is an example for using Redis to set up a simple asynchronous Publish/Subscribe system.

There is a input service that listens for HTTP requests and publishes a message in a Redis channel. On the other side there is a output service that subscribes to the channel and (as an example) prints the message it receives.

Components

The project uses Docker Compose to start three services:

• Redis
• Input service
  • Based on Flask
  • Listens for GET requests on port 5000
  • Query parameter "message" can be used to alter the message
  • Publishes messages to a channel
• Output service
  • Loop that listens for messages from the channel
  • Prints message

Run

Build and start the services:

# Build the input and output images
docker-compose build

# Start all services
docker-compose up

Now you can send a request to the input service by querying port 5000 on the host:

curl 'localhost:5000/?message=foobar'

You will see the message being printed in the Docker Compose logs.