Mirrored queues for redundancy in RabbitMQ - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a mirrored queue in RabbitMQ using policy.

RabbitMQ

rabbitmqctl set_policy [1] ".*" '{"ha-mode":"all"}'

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

Aall_mirrors

Bqueue_mirror

Cha-all

Dmirror_all

Attempts:

3 left

💡 Hint

Common Mistakes

Using an invalid or empty policy name

Confusing the policy name with the pattern

The policy name can be any identifier. Here, mirror_all is used as the policy name to apply mirroring to all queues.

2fill in blank

medium

Complete the code to set the ha-mode to mirror all queues.

RabbitMQ

rabbitmqctl set_policy mirror_all ".*" '{"ha-mode":"[1]"}'

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

Aall

Bnodes

Cexactly

Dnodes_exactly

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'nodes' or 'exactly' when wanting full mirroring

Misspelling the ha-mode value

The ha-mode value all means the queue is mirrored on all nodes in the cluster.

3fill in blank

hard

Fix the error in the command to apply the mirroring policy correctly.

RabbitMQ

rabbitmqctl set_policy mirror_all ".*" '{"ha-mode": [1]'

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

A"all"

B'all'

Call

Dall"

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting quotes around 'all'

Using single quotes inside JSON incorrectly

The value for ha-mode must be a string enclosed in double quotes inside the JSON string.

4fill in blank

hard

Fill both blanks to declare a mirrored queue named 'task_queue' with ha-mode 'all'.

RabbitMQ

rabbitmqadmin declare queue name=[1] durable=true arguments='{"[2]":"all"}'

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

Atask_queue

Bha-mode

Cha-params

Ddurable

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong argument keys like 'ha-params'

Misspelling the queue name

The queue name is task_queue. The argument key to set mirroring mode is ha-mode.

5fill in blank

hard

Fill all three blanks to create a policy named 'mirror_policy' that matches queues starting with 'task' and sets ha-mode to 'all'.

RabbitMQ

rabbitmqctl set_policy [1] "[2]" '{"[3]":"all"}'

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

Amirror_policy

B^task.*

Cha-mode

Dtask_queue

Attempts:

3 left

💡 Hint

Common Mistakes

Using queue name instead of pattern

Wrong argument key for ha-mode

The policy name is mirror_policy. The pattern to match queues starting with 'task' is ^task.*. The argument key is ha-mode.

Practice

1. What is the main purpose of using mirrored queues in RabbitMQ?

easy

A. To keep copies of messages on multiple servers for safety

B. To speed up message delivery by duplicating messages

C. To reduce the number of messages stored in the queue

D. To encrypt messages automatically during transmission

Solution

1. Step 1: Understand mirrored queues concept

   Mirrored queues replicate messages across multiple RabbitMQ nodes to ensure no message is lost if one node fails.

2. Step 2: Identify the main benefit

   This replication provides redundancy and safety, not speed or encryption.

3. Final Answer:

   To keep copies of messages on multiple servers for safety -> Option A

4. Quick Check:

   Mirroring = Redundancy and safety [OK]

Hint: Mirrored queues copy messages for safety, not speed or encryption [OK]

Common Mistakes:

• Thinking mirroring speeds up delivery
• Confusing mirroring with encryption
• Assuming mirroring reduces message count

2. Which command correctly sets a policy to mirror all queues in RabbitMQ?

easy

A. rabbitmqctl set_policy ha-all .* '{"ha-mode":"all"}'

B. rabbitmqctl set_policy ha-all ".*" '{"ha-mode":"all"}'

C. rabbitmqctl set_policy ha-all ".*" '{ha-mode:all}'

D. rabbitmqctl set_policy ha-all ".*" '{"ha-mode":all}'

Solution

1. Step 1: Review correct syntax for set_policy

   The command requires the policy name, pattern in quotes, and JSON string with keys and values in double quotes.

2. Step 2: Identify correct JSON format and quoting

   rabbitmqctl set_policy ha-all ".*" '{"ha-mode":"all"}' uses correct JSON with double quotes around keys and values and quotes the pattern ".*" properly.

3. Final Answer:

   rabbitmqctl set_policy ha-all ".*" '{"ha-mode":"all"}' -> Option B

4. Quick Check:

   Correct JSON and quoting = rabbitmqctl set_policy ha-all ".*" '{"ha-mode":"all"}' [OK]

Hint: Use double quotes inside JSON and quote pattern with ".*" [OK]

Common Mistakes:

• Missing quotes around JSON keys or values
• Not quoting the pattern string
• Using single quotes inside JSON instead of double quotes

3. Given this policy command:
rabbitmqctl set_policy ha-two ".*" '{"ha-mode":"exactly","ha-params":2}'
What will happen when a queue is created?

medium

A. The queue will be mirrored on one node only

B. The queue will be mirrored on all nodes

C. The queue will be mirrored on exactly two nodes

D. The queue will not be mirrored at all

Solution

1. Step 1: Understand ha-mode 'exactly' with ha-params

   The policy sets ha-mode to 'exactly' with ha-params 2, meaning the queue is mirrored on exactly 2 nodes.

2. Step 2: Apply policy effect on new queues

   Any queue matching ".*" will be mirrored on exactly two nodes as per the policy.

3. Final Answer:

   The queue will be mirrored on exactly two nodes -> Option C

4. Quick Check:

   ha-mode exactly + ha-params 2 = mirror on 2 nodes [OK]

Hint: ha-mode 'exactly' with ha-params sets mirror count [OK]

Common Mistakes:

• Confusing 'all' with 'exactly'
• Ignoring ha-params value
• Assuming no mirroring without ha-mode 'all'

4. You set this policy:
rabbitmqctl set_policy ha-all ".*" '{"ha-mode":"all"}'
But queues are not mirrored. What is the likely problem?

medium

A. The policy requires a restart of the queue or server to apply

B. The pattern ".*" does not match queue names

C. The policy was set but RabbitMQ was not restarted

D. The JSON syntax is incorrect

Solution

1. Step 1: Check policy application behavior

   Policies apply only to new queues or queues restarted after policy set.

2. Step 2: Identify why existing queues are not mirrored

   Existing queues created before policy need to be deleted or restarted to apply mirroring.

3. Final Answer:

   The policy requires a restart of the queue or server to apply -> Option A

4. Quick Check:

   Policy applies only on new or restarted queues [OK]

Hint: Policies apply only to new or restarted queues [OK]

Common Mistakes:

• Thinking RabbitMQ restart is needed
• Assuming pattern ".*" never matches
• Believing JSON syntax is wrong when it is correct

5. You want to ensure a queue named task_queue is mirrored on at least 3 nodes but no more than 5 using a range specification in ha-params. Which policy configuration achieves this?

hard

A. rabbitmqctl set_policy ha-range "^task_queue$" '{"ha-mode":"nodes","ha-params":["node1","node2","node3"]}'

B. rabbitmqctl set_policy ha-minmax ".*" '{"ha-mode":"exactly","ha-params":3}'

C. rabbitmqctl set_policy ha-minmax "^task_queue$" '{"ha-mode":"nodes","ha-params":["node1","node2","node3","node4","node5"]}'

D. rabbitmqctl set_policy ha-minmax "^task_queue$" '{"ha-mode":"exactly","ha-params":"3-5"}'

Solution

1. Step 1: Understand ha-mode 'exactly' with range ha-params

   ha-mode 'exactly' with ha-params as string like '3-5' dynamically mirrors the queue on a number of replicas between 3 and 5.

2. Step 2: Identify correct command

   rabbitmqctl set_policy ha-minmax "^task_queue$" '{"ha-mode":"exactly","ha-params":"3-5"}' matches the queue exactly and uses range specification.

3. Step 3: Check other options

   B uses fixed exactly 3 on all queues; C uses fixed nodes list of 5; D uses fixed nodes list of 3.

4. Final Answer:

   rabbitmqctl set_policy ha-minmax "^task_queue$" '{"ha-mode":"exactly","ha-params":"3-5"}' -> Option D

5. Quick Check:

   ha-mode exactly + ha-params "3-5" = dynamic range 3-5 [OK]

Hint: Use ha-mode 'exactly' with ha-params "3-5" for range [OK]

Common Mistakes:

• Using 'exactly' with fixed integer instead of range string
• Not matching queue name exactly
• Using 'nodes' mode with fixed list instead of range