Event sourcing with RabbitMQ - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a durable queue named 'events'.

RabbitMQ

channel.queue_declare(queue='events', durable=[1])

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

ATrue

BFalse

CNone

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using False makes the queue non-durable, risking message loss.

Setting durable=True ensures the queue survives RabbitMQ restarts, which is important for event sourcing.

2fill in blank

medium

Complete the code to publish a message to the 'events' exchange with routing key 'user.created'.

RabbitMQ

channel.basic_publish(exchange='events', routing_key=[1], body=message)

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

A'events'

B'user.updated'

C'order.created'

D'user.created'

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong routing keys causes messages to be lost or misrouted.

The routing key 'user.created' directs the message to queues bound with this key, matching the event type.

3fill in blank

hard

Fix the error in the code to consume messages from the 'events' queue with manual acknowledgments.

RabbitMQ

channel.basic_consume(queue='events', on_message_callback=callback, auto_ack=[1])

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

ATrue

BNone

CFalse

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using True causes messages to be acknowledged immediately, risking loss.

Setting auto_ack=False means the consumer must manually acknowledge messages, which is safer for event sourcing.

4fill in blank

hard

Fill both blanks to declare a topic exchange named 'events' and bind the 'user_events' queue to receive all user-related events.

RabbitMQ

channel.exchange_declare(exchange='events', exchange_type=[1])
channel.queue_bind(queue='user_events', exchange='events', routing_key=[2])

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

A'topic'

B'direct'

C'user.*'

D'#'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'direct' exchange type does not support pattern matching.

A topic exchange allows routing keys with patterns like 'user.*' to match all user events.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that stores event data for events with version greater than 1.

RabbitMQ

event_data = {event['id']: event[1] for event in events if event['version'] [2] [3]

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

A['data']

B>

C1

D['payload']

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong keys or comparison operators causes incorrect filtering or data extraction.

This comprehension collects the 'payload' of events where the version is greater than 1, using the event ID as key.

Practice

1. What is the main purpose of event sourcing in RabbitMQ?

easy

A. To record all changes as a sequence of events

B. To delete old messages automatically

C. To speed up message delivery by skipping queues

D. To encrypt messages before sending

Solution

1. Step 1: Understand event sourcing concept

   Event sourcing means storing every change as an event, not just the current state.

2. Step 2: Connect event sourcing to RabbitMQ

   RabbitMQ can store and forward these events reliably using exchanges and queues.

3. Final Answer:

   To record all changes as a sequence of events -> Option A

4. Quick Check:

   Event sourcing = record all changes as events [OK]

Hint: Event sourcing means saving every change as an event [OK]

Common Mistakes:

• Thinking event sourcing deletes old data
• Confusing event sourcing with encryption
• Assuming event sourcing skips queues

2. Which RabbitMQ component is responsible for routing events to queues based on routing keys?

easy

A. Queue

B. Binding

C. Channel

D. Exchange

Solution

1. Step 1: Identify RabbitMQ components

   Exchanges receive messages and decide where to send them using routing keys.

2. Step 2: Role of routing keys and bindings

   Bindings connect exchanges to queues, but routing decisions happen inside exchanges.

3. Final Answer:

   Exchange -> Option D

4. Quick Check:

   Routing keys route messages via exchanges [OK]

Hint: Exchanges route messages using routing keys [OK]

Common Mistakes:

• Confusing bindings as routing decision makers
• Thinking queues route messages
• Mixing channels with routing

3. Given this RabbitMQ setup:

channel.exchange_declare(exchange='events', exchange_type='direct')
channel.queue_declare(queue='order_events')
channel.queue_bind(queue='order_events', exchange='events', routing_key='order.created')
channel.basic_publish(exchange='events', routing_key='order.created', body='Order123')

What happens when the message is published?

medium

A. Message causes an error due to missing routing key

B. Message is discarded because no queue matches

C. Message is sent to 'order_events' queue

D. Message is sent to all queues bound to 'events' exchange

Solution

1. Step 1: Analyze exchange and queue binding

   The 'events' exchange is direct type, routing key 'order.created' binds to 'order_events' queue.

2. Step 2: Check message publish routing

   Message with routing key 'order.created' matches binding, so it goes to 'order_events' queue.

3. Final Answer:

   Message is sent to 'order_events' queue -> Option C

4. Quick Check:

   Direct exchange routes by exact routing key [OK]

Hint: Direct exchange sends message only to matching routing key queue [OK]

Common Mistakes:

• Assuming message goes to all queues
• Thinking message is discarded without error
• Forgetting routing key is required

4. You wrote this code to bind a queue but it doesn't receive messages:

channel.queue_bind(queue='events_queue', exchange='events_exchange', routing_key='user.updated')

What is the most likely reason messages are not received?

medium

A. The queue was not declared before binding

B. The routing key used in publishing does not match 'user.updated'

C. The exchange type does not support routing keys

D. The channel was closed before binding

Solution

1. Step 1: Verify routing key matching

   Messages only reach queues if routing keys match bindings exactly.

2. Step 2: Check publishing routing key

   If published messages use a different routing key, queue won't get them despite binding.

3. Final Answer:

   The routing key used in publishing does not match 'user.updated' -> Option B

4. Quick Check:

   Routing keys must match for delivery [OK]

Hint: Routing keys must match exactly to deliver messages [OK]

Common Mistakes:

• Assuming exchange type blocks routing keys
• Forgetting to declare queue before binding
• Not checking if channel is open

5. You want to implement event sourcing with RabbitMQ to track user actions. Which setup best ensures all user events are stored and can be replayed later?

hard

A. Use a topic exchange with queues bound by event patterns, and enable message persistence and acknowledgments

B. Use a fanout exchange to broadcast events to multiple queues, each storing events for different services

C. Use a direct exchange with one queue per event type, but do not persist messages after consumption

D. Use a headers exchange without bindings, relying on message headers only

Solution

1. Step 1: Understand event sourcing needs

   Event sourcing requires storing all events reliably and replaying them later.

2. Step 2: Evaluate exchange types and persistence

   Topic exchange allows flexible routing by event patterns; persistence and acknowledgments ensure events are saved and not lost.

3. Step 3: Compare options

   Fanout broadcasts but may not filter; direct without persistence loses events; headers without bindings is unreliable.

4. Final Answer:

   Use a topic exchange with queues bound by event patterns, and enable message persistence and acknowledgments -> Option A

5. Quick Check:

   Topic exchange + persistence = reliable event sourcing [OK]

Hint: Use topic exchange with persistence for flexible, reliable event storage [OK]

Common Mistakes:

• Ignoring message persistence
• Using fanout without filtering
• Relying on headers exchange without bindings