Event choreography vs orchestration in Kafka - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to publish an event to a Kafka topic named 'orders'.

Kafka

producer.send(new ProducerRecord<>("[1]", orderId, orderData));

Drag options to blanks, or click blank then click option'

Aorders

Bpayments

Cshipments

Dinventory

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong topic name causes events to be sent to unrelated services.

Misspelling the topic name leads to runtime errors.

The event must be sent to the 'orders' topic to notify other services about new orders.

2fill in blank

medium

Complete the code to consume events from the 'payments' topic.

Kafka

consumer.subscribe(Collections.singletonList("[1]"));

Drag options to blanks, or click blank then click option'

Apayments

Borders

Cshipments

Dinventory

Attempts:

3 left

💡 Hint

Common Mistakes

Subscribing to the wrong topic means missing important events.

Using an empty or null topic list causes errors.

Subscribing to the 'payments' topic allows the service to react to payment events.

3fill in blank

hard

Fix the error in the code that tries to orchestrate order processing by sending a command event.

Kafka

producer.send(new ProducerRecord<>("[1]", orderId, command));

Drag options to blanks, or click blank then click option'

Aorder-updates

Border-events

Corder-choreography

Dorder-commands

Attempts:

3 left

💡 Hint

Common Mistakes

Sending commands to event topics mixes orchestration with choreography.

Using a generic topic name causes confusion in message handling.

Commands should be sent to a dedicated 'order-commands' topic for orchestration.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that maps service names to their event topics only if the service is part of choreography.

Kafka

service_topics = {service: [1] for service in services if service [2] choreography_services}

Drag options to blanks, or click blank then click option'

Aservice + "-events"

Bservice == "payment"

Cin

Dservice != "inventory"

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' instead of 'in' for membership tests.

Not concatenating the '-events' suffix correctly.

The comprehension builds topic names by adding '-events' to service names that are in the choreography list.

5fill in blank

hard

Fill all three blanks to filter events with status 'completed' and map their IDs to payloads in a dictionary comprehension.

Kafka

completed_events = {event[1]: event[2] for event in events if event[3] == "completed"}

Drag options to blanks, or click blank then click option'

A.id

B.payload

C.status

D.type

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong property names like '.type' instead of '.status'.

Mixing keys and values in the comprehension.

This comprehension creates a dictionary where keys are event IDs and values are payloads, filtering only events with status 'completed'.

Practice

1. What is the main difference between event choreography and event orchestration in Kafka-based systems?

easy

A. Choreography lets services react independently; orchestration uses a central controller.

B. Choreography requires a central controller; orchestration lets services react independently.

C. Both use a central controller but differ in message format.

D. Choreography is synchronous; orchestration is asynchronous.

Solution

1. Step 1: Understand event choreography

   Event choreography means each service listens and reacts to events on its own without a central manager.

2. Step 2: Understand event orchestration

   Event orchestration means a central controller tells services what to do and when, managing the flow.

3. Final Answer:

   Choreography lets services react independently; orchestration uses a central controller. -> Option A

4. Quick Check:

   Choreography = independent reaction, Orchestration = central control [OK]

Hint: Choreography = no boss; orchestration = boss controls flow [OK]

Common Mistakes:

• Confusing which uses a central controller
• Thinking both require central control
• Mixing synchronous and asynchronous concepts

2. Which Kafka component is typically used in event orchestration to coordinate services?

easy

A. Kafka Topics with independent consumers

B. A central orchestrator service producing commands

C. Kafka Connect for data integration

D. Kafka Streams for independent event processing

Solution

1. Step 1: Identify orchestration role

   Orchestration needs a central service to control and send commands to other services.

2. Step 2: Match Kafka components

   Kafka Topics and Streams are used for event flow, but orchestration requires a central orchestrator producing commands.

3. Final Answer:

   A central orchestrator service producing commands -> Option B

4. Quick Check:

   Orchestration = central orchestrator service [OK]

Hint: Orchestration needs a central command sender [OK]

Common Mistakes:

• Choosing Kafka Topics as the controller
• Confusing Kafka Connect with orchestration
• Thinking Kafka Streams alone orchestrates

3. Given this Kafka event flow in choreography style:

Service A publishes event 'OrderCreated' to topic 'orders'.
Service B listens to 'orders' and publishes 'PaymentProcessed' to topic 'payments'.
Service C listens to 'payments' and updates inventory.

What happens if Service B fails to publish 'PaymentProcessed' event?

medium

A. Service C will not update inventory because it never receives the event.

B. Service C updates inventory anyway because it listens to 'orders'.

C. Service A retries publishing 'OrderCreated' event automatically.

D. A central orchestrator will resend 'PaymentProcessed' event.

Solution

1. Step 1: Trace event flow in choreography

   Service A publishes 'OrderCreated', Service B reacts and publishes 'PaymentProcessed', Service C listens to 'payments'.

2. Step 2: Analyze failure impact

   If Service B fails to publish 'PaymentProcessed', Service C never receives that event and cannot update inventory.

3. Final Answer:

   Service C will not update inventory because it never receives the event. -> Option A

4. Quick Check:

   Missing event means downstream service does not act [OK]

Hint: In choreography, missing event stops downstream actions [OK]

Common Mistakes:

• Assuming Service C listens to 'orders' directly
• Thinking Service A retries automatically
• Expecting a central orchestrator in choreography

4. You have this orchestration code snippet controlling Kafka services:

orchestrator.sendCommand('ServiceB', 'ProcessPayment')
orchestrator.sendCommand('ServiceC', 'UpdateInventory')

But Service C updates inventory before Service B processes payment. What is the likely problem?

medium

A. Service C is ignoring commands from the orchestrator.

B. Service B is not subscribed to the correct Kafka topic.

C. Commands are sent asynchronously without waiting for Service B to finish.

D. Kafka topics are misconfigured causing message loss.

Solution

1. Step 1: Understand orchestration command flow

   Orchestrator sends commands to services in order, expecting sequential execution.

2. Step 2: Identify asynchronous issue

   If commands are sent asynchronously without waiting for Service B to complete, Service C may act too early.

3. Final Answer:

   Commands are sent asynchronously without waiting for Service B to finish. -> Option C

4. Quick Check:

   Orchestration needs ordered, awaited commands [OK]

Hint: Orchestration requires waiting for each command to finish [OK]

Common Mistakes:

• Blaming Kafka topic subscription
• Assuming Service C ignores commands
• Thinking message loss causes order issue

5. You want to design a Kafka system for an online store where payment processing must strictly happen before inventory update, but you want to avoid a central orchestrator. Which approach fits best and how to ensure order?

hard

A. Use choreography but rely on manual retries to fix order issues.

B. Use event orchestration with a central controller sending commands in order to services.

C. Use orchestration but allow services to process events independently without waiting.

D. Use event choreography with services emitting events and consumers processing in sequence using Kafka partitions and consumer groups.

Solution

1. Step 1: Identify requirement

   Payment must happen before inventory update, but no central orchestrator allowed.

2. Step 2: Choose choreography with ordering

   Event choreography fits because services react independently. To ensure order, use Kafka partitions and consumer groups to process events in sequence.

3. Final Answer:

   Use event choreography with services emitting events and consumers processing in sequence using Kafka partitions and consumer groups. -> Option D

4. Quick Check:

   Choreography + Kafka ordering = correct sequence without central control [OK]

Hint: Choreography + Kafka partitions ensure order without central control [OK]

Common Mistakes:

• Choosing orchestration despite no central controller allowed
• Ignoring Kafka partition ordering
• Relying on manual retries for order