Event choreography vs orchestration in Kafka - Hands-On Comparison

Event Choreography vs Orchestration with Kafka

📖 Scenario: Imagine you are building a simple online store system where different services communicate using Kafka events. You want to understand the difference between event choreography and orchestration by implementing both approaches.

🎯 Goal: Build two simple Kafka event-driven flows: one using event choreography where services react to events independently, and one using orchestration where a central controller manages the flow.

📋 What You'll Learn

Create Kafka topics for order events

Set up event producers and consumers

Implement event choreography with independent consumers

Implement event orchestration with a central orchestrator service

Print messages showing the flow of events

💡 Why This Matters

🌍 Real World

Event-driven systems like online stores, payment processing, and microservices often use Kafka to communicate asynchronously.

💼 Career

Understanding event choreography and orchestration helps you design scalable, maintainable distributed systems and work effectively with Kafka in real jobs.

1

Create Kafka topics and initial order event

Create a Kafka topic called orders and produce an initial order event with the key order-123 and value {"status": "created"}.

Kafka

# Your code here to create topic 'orders' and produce initial order event

Need a hint?

Use KafkaProducer to send a JSON event with key order-123 to the orders topic.

2

Set up a configuration variable for event status to listen for

Create a variable called listen_status and set it to created to filter events with this status.

Kafka

from kafka import KafkaProducer
import json

producer = KafkaProducer(bootstrap_servers='localhost:9092', value_serializer=lambda v: json.dumps(v).encode('utf-8'))

# Produce initial order created event
producer.send('orders', key=b'order-123', value={'status': 'created'})
producer.flush()

# Create a variable called listen_status and set it to 'created'
# Your code here

Need a hint?

Just create a variable named listen_status and assign the string 'created' to it.

3

Implement event choreography consumer reacting to 'created' events

Write a Kafka consumer that listens to the orders topic and prints Order {key} received with status {status} only if the event's status matches the listen_status variable.

Kafka

from kafka import KafkaProducer
import json
from kafka import KafkaConsumer

producer = KafkaProducer(bootstrap_servers='localhost:9092', value_serializer=lambda v: json.dumps(v).encode('utf-8'))

# Produce initial order created event
producer.send('orders', key=b'order-123', value={'status': 'created'})
producer.flush()

# Configuration variable to listen for specific event status
listen_status = 'created'

# Create a KafkaConsumer to listen to 'orders' topic
# For each message, decode JSON and check if status equals listen_status
# If yes, print the message as specified
# Your code here

Need a hint?

Use KafkaConsumer to read from orders. Decode the key and value, check if status matches listen_status, then print the message.

4

Print the final message showing event choreography output

Print the exact message Order order-123 received with status created to show the event choreography flow.

Kafka

from kafka import KafkaProducer
import json
from kafka import KafkaConsumer

producer = KafkaProducer(bootstrap_servers='localhost:9092', value_serializer=lambda v: json.dumps(v).encode('utf-8'))

# Produce initial order created event
producer.send('orders', key=b'order-123', value={'status': 'created'})
producer.flush()

# Configuration variable to listen for specific event status
listen_status = 'created'

# Event choreography consumer
consumer = KafkaConsumer('orders', bootstrap_servers='localhost:9092', auto_offset_reset='earliest', value_deserializer=lambda v: json.loads(v))

for message in consumer:
    key = message.key.decode('utf-8') if message.key else 'unknown'
    status = message.value.get('status', '')
    if status == listen_status:
        print(f"Order {key} received with status {status}")
        break

# Print the final message below
# Your code here

Need a hint?

Just print the exact message to show the event choreography result.