You work for a car manufacturer and have set up a data pipeline using Google Cloud Pub/Sub to capture anomalous sensor events. You are using a push subscription in Cloud Pub/Sub that calls a custom HTTPS endpoint that you have created to take action of these anomalous events as they occur. Your custom
HTTPS endpoint keeps getting an inordinate amount of duplicate messages. What is the most likely cause of these duplicate messages?
In Google Cloud Pub/Sub, duplicate messages can occur if the custom endpoint does not acknowledge the messages within the acknowledgement deadline. When a push subscription is used, Pub/Sub expects an acknowledgment from the endpoint to confirm that the message has been received and processed. If this acknowledgment is not received within the set deadline, Pub/Sub assumes the message was not processed successfully and will attempt to redeliver it, resulting in duplicate messages. Hence, ensuring that the custom HTTPS endpoint acknowledges messages promptly is crucial to prevent this situation.
The Answer should be D. The custom endpoint is not acknowledging the message, that is the reason for Pub/Sub to send the message again and again. Not B.
Answer D. https://cloud.google.com/pubsub/docs/troubleshooting#dupes
The correct answer is D, because it's how Pub/Sub works. Documentation here: https://cloud.google.com/pubsub/docs/troubleshooting#dupes
It should be D https://cloud.google.com/pubsub/docs/troubleshooting#dupes
D is the correct answer.
No acknowledgment -> Answer B. Moderators please update your answer
D for sure
D for sure
The correct answer is: D. Your custom endpoint is not acknowledging messages within the acknowledgement deadline.
In Google Cloud Pub/Sub, when you use a push subscription, messages are delivered to the specified endpoint (in this case, your custom HTTPS endpoint). The acknowledgment deadline is the time given to the endpoint to acknowledge that it has received and processed the message. If the acknowledgment is not received within the deadline, Pub/Sub may consider the message as unacknowledged and may attempt redelivery, which can lead to duplicate messages. You should ensure that your custom HTTPS endpoint acknowledges messages within the acknowledgment deadline to prevent duplicate messages from being sent. Additionally, it's essential to handle messages in an idempotent way, so even if duplicates do occur, the action taken by your endpoint doesn't have unintended consequences.
d is correct
I mistakenly answered by D, but it's indeed B. Here is the explanation: https://www.youtube.com/watch?v=KObJkda4ZfY
And where exactly in this video it's stated that this is caused by the invalid cert?
if there were an out of date certificate then nothing would get through. D
D should be the answer. If acknowlegement is not received back to pub/sub , pub/sub may resend meassages.
D - If a message has not been acknowledged within its acknowledgement deadline, Dataflow attempts to maintain the lease on the message by repeatedly extending the acknowledgement deadline to prevent redelivery from Pub/Sub. However this is best effort and there is a possibility that messages may be redelivered. This can be monitored using metrics listed here. https://cloud.google.com/blog/products/data-analytics/handling-duplicate-data-in-streaming-pipeline-using-pubsub-dataflow
Agree with previous explanations regarding validity of D
After re-reading the question it seem to me that it is asking for a root cause. It is possible that the most common cause of this symptom is and expired certificate. Once expired duplicates would be received for every message.