Message broker app

Message broker is a Node.JS application that allows multiple producers and consumers to send and receive messages. Two messaging models are supported:

• queueing
  • asynchronous communication, the producer and consumer of the message do not need to interact with the broker at the same time. Messages in the broker are stored until a given consumer retrieves them.
• publish-subscribe
  • broker keeps a list of the subscribed consumers, but when a message is received it is not sent immediately to all the consumers. Instead he exposes send operation where all the stored messages are broadcasted to all the subscribed consumers.

Supported actions:

• Broker:

  • receive messages from publishers and store them for future consumption
  • add/remove message consumers
  • on a request from given consumer to send him all the messages
  • on his own to send the messages to the subscribed consumers

• Producer:

  • send messages to the broker

• Consumer:

  • consume messages from the broker (initiated by the consumer)
  • subscribe/unsubscribe to the broker
  • receive messages from the broker (initiated by the broker)
    • when the broker wants to broadcast the messages to the subscribed consumers

Broker with 2 publishers and 2 subscribers

Postman (collection here)

Tech stack

Database

• the messages in the broker are persisted in PostgreSQL instance hosted on Heroku
• the db contains only one table for messages (id, content, sender, created_at)
• the data access is through Sequelize (Node.js ORM for PostgreSQL)

Commands

To install the dependencies: npm install and to build the typescript files: tsc -w

To start broker, 2 producers and 2 consumers in separate terminals run:

npm run broker
npm run firstProducer
npm run secondProducer
npm run firstConsumer
npm run secondConsumer

To run the tests:

npm run testBroker
npm run testProducer
npm run testConsumer

Docker:

docker build -t node-broker .
docker run -it -p 3000:3000 node-broker

To build the first consumer and producer:

docker build -t node-first-consumer -f ./consumer/Dockerfile .
docker build -t node-first-producer -f ./producer/Dockerfile .

Made with ❤️ by Kristian Martinoski