Is my approach right when using Cloud Functions, Pub/Sub and Dead-letter queues/topics?

user_11450710 0
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I'm developing my first microservice, I chose to deploy it in a Cloud Functions service with messaging done via Pub/Sub.

The Cloud Functions service is triggered by events (published messages) in a Pub/Sub topic, the microservice processes the message and so far so good. I know that Cloud Functions guarantees the acknowledgement and delivery of messages, and that's good.

The Cloud Functions service has automatic retrying: If I throw an exception in the code, a new program execution occurs. In order to avoid looping executions on consecutive failures, I introduced an if conditional that checks the 'age' of the message, and since I don't want to simply discard the message, I send/publish it to another Pub/Sub topic that I've named "my-dead-letter-queue" topic.

As I am unsure about everything now, I ask you: Is my approach good enough? What would you do instead considering Cloud Functions microservices and Pub/Sub messaging?

google-cloud-pubsub google-cloud-functions google-cloud-platform
2 Answers

Yes your approach is good if you want to base on the message age the rule to send your bad messages in a dead letter topic.

If you want to do it on the number of fails (after 5 fails, put the message in the dead letter topic), you can't achieve that with a cloud function directly plugged on PubSub. You need to create an HTTP functions and then to create PubSub push subscription, on which you can set a dead letter topic (min 5 fails before sending the message automatically in a dead letter topic).

The advantage of that second solution is that you haven't to process the message and to push it to pubsub in your Cloud Functions (all processing time cost money), it's automatic and therefore you save money ;)

user_113725930

The approach you are trying to use is good every time you get an exception and insert it into your dead letter topic. It will work every time you try to achieve exception handling without any problem in the future, but if you would want to throw in there more exceptions, you should consider changing how you manage the exceptions.

Here you can see how you can publish the messages within gcloud command-line

user_107828090
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