[Solved] Consider this code snippet using Google Cloud Pub/Sub subscriber client: def callback(message): print(f"Received: {message.data.decode('utf-8')}") # No acknowledgment called here subscriber.... | GCP

GCP - Cloud Pub/Sub

Consider this code snippet using Google Cloud Pub/Sub subscriber client:

def callback(message):
    print(f"Received: {message.data.decode('utf-8')}")
    # No acknowledgment called here

subscriber.subscribe(subscription_path, callback=callback)

What will happen to the messages if the callback never calls message.ack()?

AMessages will be acknowledged automatically after printing.

BMessages will be lost immediately after printing.

CMessages will be redelivered until acknowledged or retention expires.

DMessages will be sent to a dead-letter topic instantly.

Step-by-Step Solution

Solution:

Step 1: Understand callback behavior without ack
If message.ack() is not called, Pub/Sub considers the message unacknowledged.
Step 2: Effect on message delivery
Unacknowledged messages are redelivered repeatedly until acknowledged or retention period expires.
Final Answer:
Messages will be redelivered until acknowledged or retention expires. -> Option C
Quick Check:
No ack means redelivery until retention ends [OK]

Quick Trick: No ack means message redelivery until retention ends [OK]

Common Mistakes:

Assuming messages auto-acknowledge after callback
Thinking messages are lost immediately without ack
Believing messages go to dead-letter topic without config

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Consider this code snippet using Google Cloud Pub/Sub subscriber client:

Step 1: Understand callback behavior without ack

Step 2: Effect on message delivery

Final Answer:

Quick Check:

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