Direct exchange in RabbitMQ - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a direct exchange named 'logs'.

RabbitMQ

channel.exchange_declare(exchange='logs', exchange_type='[1]')

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

Adirect

Btopic

Cfanout

Dheaders

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'fanout' instead of 'direct' will broadcast messages to all queues.

Using 'topic' requires pattern matching, not exact routing keys.

The direct exchange type routes messages with a specific routing key to queues bound with that key.

2fill in blank

medium

Complete the code to bind the queue 'error_logs' to the exchange 'logs' with routing key 'error'.

RabbitMQ

channel.queue_bind(queue='error_logs', exchange='logs', routing_key='[1]')

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

Adebug

Berror

Cwarning

Dinfo

Attempts:

3 left

💡 Hint

Common Mistakes

Using a routing key that does not match the message's routing key will prevent message delivery.

Binding to the wrong exchange name will cause errors.

Binding with routing key 'error' ensures that messages sent with this key are routed to the 'error_logs' queue.

3fill in blank

hard

Fix the error in the code to publish a message with routing key 'info' to the 'logs' exchange.

RabbitMQ

channel.basic_publish(exchange='logs', routing_key='[1]', body='System started')

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

Ainfo

Berror

Cwarning

Dstart

Attempts:

3 left

💡 Hint

Common Mistakes

Using a routing key that does not match any queue bindings results in message loss.

Misspelling the routing key causes routing failures.

The routing key must match the intended message type, here 'info' to route correctly.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that maps routing keys to their message counts only if the count is greater than 5.

RabbitMQ

{key: counts[1] for key in counts if counts[key][2] 5}

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

A.get(key, 0)

B<

C>

D[]

Attempts:

3 left

💡 Hint

Common Mistakes

Using [] instead of .get() can cause errors if key is missing.

Using '<' will filter the wrong keys.

The comprehension uses counts.get(key, 0) to safely get counts and filters keys with counts greater than 5.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps uppercase routing keys to their counts only if count is greater than 10.

RabbitMQ

{ [1]: [2] for [3] in counts if counts[[3]] > 10 }

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

Akey.upper()

Bcounts[key]

Ckey

Dcounts.get(key, 0)

Attempts:

3 left

💡 Hint

Common Mistakes

Using counts.get(key, 0) is safe but unnecessary if keys exist.

Using the wrong variable name in the loop causes errors.

The comprehension maps uppercase keys to their counts, iterating over keys and filtering counts greater than 10.

Practice

1. What is the main behavior of a direct exchange in RabbitMQ?

easy

A. It broadcasts messages to all queues regardless of routing keys.

B. It routes messages based on pattern matching of routing keys.

C. It routes messages to queues with an exact matching routing key.

D. It stores messages without routing them to any queue.

Solution

1. Step 1: Understand direct exchange routing

   A direct exchange routes messages only to queues whose binding key exactly matches the message's routing key.

2. Step 2: Compare with other exchange types

   Unlike fanout (broadcast) or topic (pattern matching) exchanges, direct exchange requires exact key match.

3. Final Answer:

   It routes messages to queues with an exact matching routing key. -> Option C

4. Quick Check:

   Direct exchange = exact routing key match [OK]

Hint: Direct exchange matches routing keys exactly [OK]

Common Mistakes:

• Confusing direct with fanout exchange behavior
• Thinking direct exchange uses pattern matching
• Assuming messages go to all queues regardless of keys

2. Which of the following is the correct way to declare a direct exchange named logs_direct using RabbitMQ's command line tool rabbitmqadmin?

easy

A. rabbitmqadmin add exchange logs_direct type=fanout

B. rabbitmqadmin declare exchange name=logs_direct type=direct

C. rabbitmqadmin create exchange logs_direct direct

D. rabbitmqadmin declare exchange logs_direct type=topic

Solution

1. Step 1: Recall rabbitmqadmin syntax for exchange declaration

   The correct syntax is: rabbitmqadmin declare exchange name=EXCHANGE_NAME type=EXCHANGE_TYPE

2. Step 2: Match the command to declare a direct exchange named logs_direct

   rabbitmqadmin declare exchange name=logs_direct type=direct matches the syntax and specifies type=direct correctly.

3. Final Answer:

   rabbitmqadmin declare exchange name=logs_direct type=direct -> Option B

4. Quick Check:

   rabbitmqadmin declare exchange + name + type=direct [OK]

Hint: Use 'declare exchange name=... type=direct' syntax [OK]

Common Mistakes:

• Using 'create' instead of 'declare'
• Wrong exchange type like fanout or topic
• Missing 'name=' before exchange name

3. Given a direct exchange ex_direct with two queues bound: queue1 with routing key info and queue2 with routing key error. If a message is published with routing key info, which queues will receive the message?

medium

A. Only queue1

B. Only queue2

C. Both queue1 and queue2

D. No queue receives the message

Solution

1. Step 1: Identify bindings and routing keys

   queue1 is bound with routing key 'info', queue2 with 'error'. The message has routing key 'info'.

2. Step 2: Apply direct exchange routing rule

   Direct exchange routes messages only to queues with exact matching routing keys. So only queue1 matches.

3. Final Answer:

   Only queue1 -> Option A

4. Quick Check:

   Message routing key = queue binding key [OK]

Hint: Message goes only to queues with exact routing key match [OK]

Common Mistakes:

• Assuming message goes to all queues
• Confusing routing keys with patterns
• Thinking queue2 also receives message

4. You declared a direct exchange and bound a queue with routing key task. However, messages published with routing key tasks are not received by the queue. What is the most likely cause?

medium

A. Message payload is empty

B. Exchange type is incorrectly set to fanout

C. Queue is not declared properly

D. Routing key mismatch between binding and message

Solution

1. Step 1: Check routing key binding and message key

   The queue is bound with routing key 'task' but messages are sent with 'tasks'. These keys differ.

2. Step 2: Understand direct exchange routing behavior

   Direct exchange requires exact routing key match. A mismatch means the message won't be routed to the queue.

3. Final Answer:

   Routing key mismatch between binding and message -> Option D

4. Quick Check:

   Exact routing key match needed [OK]

Hint: Check routing keys for exact spelling match [OK]

Common Mistakes:

• Assuming fanout exchange routes by keys
• Blaming queue declaration without checking keys
• Thinking empty payload blocks routing

5. You have a direct exchange ex_direct with three queues bound: Q1 with routing key red, Q2 with routing key blue, and Q3 with routing key red. If you publish a message with routing key red, which queues receive the message and why?

hard

A. Q1 and Q3 both receive it because they share the same routing key

B. No queue receives it because multiple bindings cause conflict

C. Only Q3 receives it because it was bound last

D. Only Q1 receives it because it was bound first

Solution

1. Step 1: Identify queues bound with routing key 'red'

   Q1 and Q3 are both bound with routing key 'red'. Q2 is bound with 'blue'.

2. Step 2: Apply direct exchange routing logic

   Direct exchange routes messages to all queues with matching routing keys. So both Q1 and Q3 receive the message.

3. Final Answer:

   Q1 and Q3 both receive it because they share the same routing key -> Option A

4. Quick Check:

   Multiple queues with same key all get message [OK]

Hint: Multiple queues with same key all get messages [OK]

Common Mistakes:

• Thinking only one queue receives the message
• Assuming binding order affects routing
• Believing multiple bindings cause conflicts