Dead letter queues in HLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a dead letter queue in the messaging system.

HLD

dead_letter_queue = MessageQueue(name=[1])

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A"dead_letter_queue"

B"main_queue"

C"processing_queue"

D"retry_queue"

Attempts:

3 left

💡 Hint

Common Mistakes

Using the main queue name instead of a separate dead letter queue name.

The dead letter queue should be named distinctly, commonly as "dead_letter_queue" to separate it from main processing queues.

2fill in blank

medium

Complete the code to route failed messages to the dead letter queue.

HLD

if message.processing_failed:
    [1].send(message)

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Aretry_queue

Bdead_letter_queue

Cmain_queue

Dprocessing_queue

Attempts:

3 left

💡 Hint

Common Mistakes

Sending failed messages back to the main queue or retry queue without limit.

Failed messages should be sent to the dead letter queue for later inspection or handling.

3fill in blank

hard

Fix the error in the dead letter queue configuration code.

HLD

dead_letter_queue = MessageQueue(name="dead_letter_queue", max_retries=[1])

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A5

B-1

C0

DNone

Attempts:

3 left

💡 Hint

Common Mistakes

Setting max_retries to a positive number causing infinite retry loops.

The dead letter queue should not retry messages, so max_retries should be set to 0.

4fill in blank

hard

Fill both blanks to define a retry policy that sends messages to the dead letter queue after max attempts.

HLD

retry_policy = RetryPolicy(max_attempts=[1], on_failure=[2])

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A3

Bdead_letter_queue

Cmain_queue

Dretry_queue

Attempts:

3 left

💡 Hint

Common Mistakes

Sending failed messages back to main or retry queues instead of dead letter queue.

Set max_attempts to 3 and on_failure to dead_letter_queue to move messages after retries fail.

5fill in blank

hard

Fill all three blanks to create a monitoring alert for messages in the dead letter queue exceeding threshold.

HLD

if dead_letter_queue.message_count [1] [2]:
    alert_system.notify("Dead letter queue has [3] messages")

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A>

B100

C50

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using equality operator instead of greater than for threshold check.

The alert triggers when message count is greater than 100, notifying about 50 messages as an example.