Queue TTL and auto-expiry in RabbitMQ - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set a queue with a message TTL of 60000 milliseconds.

RabbitMQ

rabbitmqctl set_policy TTL "^myqueue$" '{"message-ttl": [1]' --apply-to queues

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

A60000

B6000

C600000

D60

Attempts:

3 left

💡 Hint

Common Mistakes

Using seconds instead of milliseconds

Setting TTL too low or too high by mistake

The message-ttl value is in milliseconds. 60000 means messages expire after 60 seconds.

2fill in blank

medium

Complete the code to declare a queue with auto-expiry of 300000 milliseconds using rabbitmqadmin.

RabbitMQ

rabbitmqadmin declare queue name=myqueue durable=true arguments='{"x-expires": [1]'

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

A300

B30000

C3000

D300000

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing message TTL with queue expiry

Using seconds instead of milliseconds

The x-expires argument sets the queue auto-expiry time in milliseconds. 300000 means 5 minutes.

3fill in blank

hard

Fix the error in the policy command to set queue TTL to 120000 milliseconds.

RabbitMQ

rabbitmqctl set_policy TTL "^myqueue$" '{"message-ttl": [1]' --apply-to queues

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

A120000

B1200

C12000

D"120000"

Attempts:

3 left

💡 Hint

Common Mistakes

Putting TTL value in quotes causing syntax error

Using wrong TTL value

The TTL value must be a number, not a string. So 120000 without quotes is correct.

4fill in blank

hard

Fill both blanks to declare a queue with message TTL and auto-expiry set.

RabbitMQ

rabbitmqadmin declare queue name=myqueue durable=true arguments='{"x-message-ttl": [1], "x-expires": [2]'

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

A60000

B120000

C180000

D300000

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up TTL and expiry values

Using same value for both TTL and expiry

Message TTL is set to 60000 ms (1 minute), and queue auto-expiry is set to 300000 ms (5 minutes).

5fill in blank

hard

Fill all three blanks to set a policy that applies TTL and auto-expiry to queues starting with 'task_'.

RabbitMQ

rabbitmqctl set_policy taskTTL "^task_.*" '{"message-ttl": [1], "expires": [2], "auto-delete": [3]' --apply-to queues

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

A60000

B180000

Ctrue

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Using string 'true' instead of boolean true

Confusing expires with message-ttl

The policy sets message TTL to 60000 ms, queue expires after 180000 ms, and auto-delete is enabled (true).

Practice

1. What does setting a x-message-ttl on a RabbitMQ queue do?

easy

A. It sets how long messages stay in the queue before they expire.

B. It deletes the queue after a certain time of inactivity.

C. It limits the number of messages the queue can hold.

D. It changes the priority of messages in the queue.

Solution

1. Step 1: Understand x-message-ttl meaning

   The x-message-ttl setting controls the time-to-live for messages in the queue, meaning how long each message can stay before expiring.

2. Step 2: Differentiate from queue auto-expiry

   Queue auto-expiry deletes the entire queue after inactivity, which is different from message TTL.

3. Final Answer:

   It sets how long messages stay in the queue before they expire. -> Option A

4. Quick Check:

   Message TTL = message lifetime [OK]

Hint: Message TTL controls message lifetime, not queue deletion [OK]

Common Mistakes:

• Confusing message TTL with queue auto-expiry
• Thinking TTL limits message count
• Assuming TTL changes message priority

2. Which of the following is the correct way to set a queue TTL of 60000 milliseconds in RabbitMQ using arguments?

easy

A. {"x-message-ttl":60000}

B. {"x-expires":60000}

C. {"x-max-length":60000}

D. {"x-priority":60000}

Solution

1. Step 1: Identify the correct argument for message TTL

   The argument x-message-ttl is used to set the time-to-live for messages in milliseconds.

2. Step 2: Verify other options

   x-expires is for queue auto-expiry, x-max-length limits queue size, and x-priority sets message priority, so they are incorrect here.

3. Final Answer:

   {"x-message-ttl":60000} -> Option A

4. Quick Check:

   TTL argument = x-message-ttl [OK]

Hint: Use x-message-ttl for message expiry time in ms [OK]

Common Mistakes:

• Using x-expires instead of x-message-ttl
• Confusing max-length with TTL
• Setting priority instead of TTL

3. Given a queue with x-message-ttl set to 30000 ms and a message published at time 0, what happens if the message is not consumed by 35000 ms?

medium

A. The queue is deleted after 30000 ms.

B. The message is removed from the queue automatically after 30000 ms.

C. The message stays in the queue indefinitely until consumed.

D. The message priority is increased after 30000 ms.

Solution

1. Step 1: Understand message TTL effect

   Message TTL of 30000 ms means messages expire and are removed if not consumed within 30 seconds.

2. Step 2: Apply timing to message

   Since the message is not consumed by 35000 ms (which is after 30000 ms), it will be removed automatically.

3. Final Answer:

   The message is removed from the queue automatically after 30000 ms. -> Option B

4. Quick Check:

   Message expires after TTL [OK]

Hint: Messages expire after TTL if not consumed [OK]

Common Mistakes:

• Thinking messages stay forever without consumption
• Confusing message TTL with queue deletion
• Assuming priority changes with TTL

4. You set x-expires to 60000 on a queue, but the queue is not deleted after 1 minute of inactivity. What could be the reason?

medium

A. The x-expires value must be set in seconds, not milliseconds.

B. RabbitMQ does not support queue auto-expiry.

C. The queue TTL must be set for the queue to expire.

D. The queue has active consumers or unacknowledged messages.

Solution

1. Step 1: Understand x-expires behavior

   x-expires deletes the queue after the specified time of inactivity, meaning no consumers and no unacknowledged messages.

2. Step 2: Identify why queue is not deleted

   If the queue has active consumers or unacknowledged messages, it is considered active and will not be deleted despite x-expires.

3. Final Answer:

   The queue has active consumers or unacknowledged messages. -> Option D

4. Quick Check:

   Queue expires only if inactive [OK]

Hint: Queue expires only when fully inactive (no consumers) [OK]

Common Mistakes:

• Confusing milliseconds with seconds for x-expires
• Thinking message TTL controls queue expiry
• Believing RabbitMQ lacks auto-expiry feature

5. You want a queue to automatically delete itself if unused for 2 minutes and also want messages to expire after 1 minute. Which configuration is correct?

hard

A. {"x-max-length":120000, "x-expires":60000}

B. {"x-message-ttl":120000, "x-expires":60000}

C. {"x-expires":120000, "x-message-ttl":60000}

D. {"x-expires":60000, "x-message-ttl":120000}

Solution

1. Step 1: Match time values to correct arguments

   x-expires controls queue auto-expiry after inactivity, so 2 minutes = 120000 ms should be set here. x-message-ttl controls message expiry, so 1 minute = 60000 ms goes here.

2. Step 2: Verify option correctness

   {"x-expires":120000, "x-message-ttl":60000} correctly assigns x-expires to 120000 and x-message-ttl to 60000. Other options swap or misuse these values.

3. Final Answer:

   {"x-expires":120000, "x-message-ttl":60000} -> Option C

4. Quick Check:

   Queue expiry = 120000 ms, Message TTL = 60000 ms [OK]

Hint: Set x-expires for queue, x-message-ttl for messages [OK]

Common Mistakes:

• Swapping TTL and expires values
• Using max-length instead of TTL or expires
• Confusing milliseconds with seconds