RPC vs direct API calls in RabbitMQ - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to send a message to the queue named 'task_queue'.

RabbitMQ

channel.basic_publish(exchange='', routing_key='[1]', body='Hello World!')

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

Atask_queue

Brpc_queue

Capi_queue

Dresponse_queue

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong queue name in routing_key

Confusing exchange with routing_key

The routing_key specifies the queue name. Here, 'task_queue' is the correct queue to send the message.

2fill in blank

medium

Complete the code to declare a queue for RPC server to listen on.

RabbitMQ

channel.queue_declare(queue='[1]')

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

Atask_queue

Brpc_queue

Capi_queue

Dcallback_queue

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'task_queue' instead of 'rpc_queue'

Confusing callback queue with server queue

The RPC server listens on 'rpc_queue' to receive requests.

3fill in blank

hard

Fix the error in the code to send an RPC request with a unique correlation id.

RabbitMQ

channel.basic_publish(exchange='', routing_key='rpc_queue', properties=pika.BasicProperties(correlation_id=[1]), body='Request')

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

A'corr_id_1'

B'12345'

C12345

DNone

Attempts:

3 left

💡 Hint

Common Mistakes

Using an integer instead of a string for correlation_id

Passing None as correlation_id

The correlation_id must be a string. Using quotes around the id is required.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that filters messages with a correlation id matching the request.

RabbitMQ

responses = {k: v for k, v in messages.items() if k [1] request_id and v [2] 'done'}

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

A==

B!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!=' instead of '=='

Mixing operators incorrectly

The comprehension selects items where the key equals the request_id and the value does not equal 'done'.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps request IDs to their responses if the response status is 'success'.

RabbitMQ

result = [1]: [2] for [3] in responses.items() if v == 'success'

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

Areq_id

Bresp

Creq_id, v

Dv

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing key and value names

Incorrect unpacking of items

Using wrong variable names

The comprehension maps each request ID (req_id) to its response (v) from the items (req_id, v) where the response status is 'success'.

Practice

1. What is a key difference between RabbitMQ RPC and direct API calls?

easy

A. RPC uses message queues to communicate asynchronously, while direct API calls use HTTP requests synchronously.

B. RPC requires a web browser, but direct API calls do not.

C. Direct API calls always use message queues, but RPC uses HTTP.

D. RPC is only used for database queries, direct API calls are for UI updates.

Solution

1. Step 1: Understand communication methods

   RPC in RabbitMQ uses message queues to send and receive messages asynchronously between services.

2. Step 2: Compare with direct API calls

   Direct API calls typically use HTTP requests for immediate, synchronous communication between client and server.

3. Final Answer:

   RPC uses message queues to communicate asynchronously, while direct API calls use HTTP requests synchronously. -> Option A

4. Quick Check:

   RPC = asynchronous messaging, API calls = synchronous HTTP [OK]

Hint: RPC = queues and async; API calls = HTTP and sync [OK]

Common Mistakes:

• Confusing RPC with HTTP usage
• Thinking RPC requires a browser
• Assuming direct API uses queues

2. Which of the following is the correct RabbitMQ RPC client call pattern?

easy

A. Directly call function in remote service without messaging

B. Send HTTP GET request to server endpoint

C. Send message to queue, wait for reply on callback queue

D. Open TCP socket and stream data continuously

Solution

1. Step 1: Identify RabbitMQ RPC client behavior

   The client sends a message to a request queue and waits for a response on a callback queue.

2. Step 2: Eliminate other options

   Options A, B, and D describe direct function calls, HTTP calls, or streaming, which are not RabbitMQ RPC patterns.

3. Final Answer:

   Send message to queue, wait for reply on callback queue -> Option C

4. Quick Check:

   RPC client sends request and waits on callback queue [OK]

Hint: RPC client uses request and callback queues [OK]

Common Mistakes:

• Confusing HTTP requests with RabbitMQ messaging
• Thinking RPC skips waiting for reply
• Mixing streaming with RPC calls

3. Given this RabbitMQ RPC client code snippet, what will be the output if the server replies with '42'?

client.send_request('compute', payload)
response = client.wait_for_response()
print(response)

medium

A. 42

B. None

C. Error: No response received

D. compute

Solution

1. Step 1: Analyze client request and response

   The client sends a request with 'compute' and waits for the server's reply.

2. Step 2: Understand server reply effect

   The server replies with '42', so the client receives '42' as the response and prints it.

3. Final Answer:

   42 -> Option A

4. Quick Check:

   Server reply '42' is printed by client [OK]

Hint: Output matches server reply message [OK]

Common Mistakes:

• Assuming no response means error
• Confusing request content with response
• Expecting function name printed

4. You wrote a RabbitMQ RPC client but it never receives a response. What is a likely cause?

medium

A. The server is sending HTTP responses instead of messages.

B. The client did not declare or listen on the callback queue.

C. The client is using direct API calls instead of RPC.

D. The client sent the request to the wrong HTTP endpoint.

Solution

1. Step 1: Check client callback queue setup

   In RabbitMQ RPC, the client must declare and listen on a callback queue to receive replies.

2. Step 2: Identify why no response arrives

   If the callback queue is missing or not listened to, the client won't get the server's reply message.

3. Final Answer:

   The client did not declare or listen on the callback queue. -> Option B

4. Quick Check:

   Missing callback queue causes no response [OK]

Hint: Always declare and listen on callback queue [OK]

Common Mistakes:

• Confusing HTTP endpoints with RabbitMQ queues
• Ignoring callback queue setup
• Mixing direct API calls with RPC messaging

5. You want to build a service that processes tasks reliably even if the worker is busy or down. Which approach is best?

hard

A. Use direct API calls with HTTP for immediate responses.

B. Use local function calls without messaging or HTTP.

C. Use WebSocket connections for real-time task processing.

D. Use RabbitMQ RPC to queue tasks and get replies asynchronously.

Solution

1. Step 1: Understand reliability needs

   Reliable task processing requires queuing tasks so they are not lost if workers are busy or down.

2. Step 2: Match approach to reliability

   RabbitMQ RPC uses message queues that store tasks until workers process them, supporting asynchronous replies and retries.

3. Step 3: Compare other options

   Direct API calls and WebSockets require immediate availability and do not queue tasks reliably; local calls lack distribution.

4. Final Answer:

   Use RabbitMQ RPC to queue tasks and get replies asynchronously. -> Option D

5. Quick Check:

   Reliable async processing = RabbitMQ RPC [OK]

Hint: Queue tasks with RPC for reliability, not direct API [OK]

Common Mistakes:

• Choosing direct API for reliable queuing
• Confusing WebSocket with message queue reliability
• Ignoring asynchronous processing benefits