event-sourcing

Event sourcing

Record states in a non-destructive way

Example

We have the following applications:

• One app exposing REST endpoints:
  • It is exposed at port 3001
  • It contains 2 endpoints:
    • http://localhost:3000/cats
    • http://localhost:3000/cats/{id}/events
• A Zookeeper
• Kafka to register the events

Running the example

docker-compose up
# Calling this command will consume the message
docker exec -it eventsourcing_kafka_1 /opt/kafka/bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic events --from-beginning

# Open another terminal session
# Notice in the kafka consumer, the events are appended
curl -i -X POST http://localhost:3000/cats/1/events -d '{"message": "eat"}'
curl -i -X POST http://localhost:3000/cats/1/events -d '{"message": "poop"}'
curl -i -X POST http://localhost:3000/cats/1/events -d '{"message": "annoy owner"}'

Sources

• Microsoft Azure
• Stackoverflow
• Martin Fowler