Answer-first summary for fast verification
Answer: Use an exception handling block in your Dataflow’s DoFn code to push the messages that failed to be transformed through a side output and to a new Pub/Sub topic. Use Cloud Monitoring to monitor the topic/num_unacked_messages_by_region metric on this new topic.
The correct answer is B. Implementing an exception handling block within the DoFn code in Dataflow to catch failures during processing allows you to manage errors effectively. By using a side output to redirect failed messages to a new Pub/Sub topic, you can isolate and handle these messages separately. Additionally, monitoring the 'topic/num_unacked_messages_by_region' metric on the new topic will alert you to the presence of failed messages, ensuring robust error tracking and alerting.
Author: LeetQuiz Editorial Team
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You are operating a car factory that transmits machine measurement data as messages to a Pub/Sub topic within your Google Cloud project. You have developed a Dataflow streaming job using the Apache Beam SDK to read these messages, acknowledge their receipt to Pub/Sub, apply custom business logic within a DoFn instance, and subsequently write the processed results to BigQuery. Your objective is to ensure that any message failing due to business logic errors is redirected to a separate Pub/Sub topic dedicated to monitoring and alerting. How should you accomplish this?
A
Enable retaining of acknowledged messages in your Pub/Sub pull subscription. Use Cloud Monitoring to monitor the subscription/num_retained_acked_messages metric on this subscription.
B
Use an exception handling block in your Dataflow’s DoFn code to push the messages that failed to be transformed through a side output and to a new Pub/Sub topic. Use Cloud Monitoring to monitor the topic/num_unacked_messages_by_region metric on this new topic.
C
Enable dead lettering in your Pub/Sub pull subscription, and specify a new Pub/Sub topic as the dead letter topic. Use Cloud Monitoring to monitor the subscription/dead_letter_message_count metric on your pull subscription.
D
Create a snapshot of your Pub/Sub pull subscription. Use Cloud Monitoring to monitor the snapshot/num_messages metric on this snapshot.