GCP Pub/Sub with Spring Boot: How to handle message retries and avoid duplicate processing?
I'm currently using Google Cloud Pub/Sub in a Spring Boot application to handle event-driven architecture. However, I'm working with issues with message retries causing duplicate processing. I've set up my subscriber as follows: ```java @Bean public Subscriber pubSubSubscriber() { ProjectSubscriptionName subscriptionName = ProjectSubscriptionName.of("my-project-id", "my-subscription-id"); MessageReceiver receiver = (PubsubMessage message, AckReplyConsumer consumer) -> { try { // Process the message processMessage(message); consumer.ack(); } catch (Exception e) { // Log the behavior but do not ack, expect re-delivery System.err.println("behavior processing message: " + e.getMessage()); } }; return Subscriber.newBuilder(subscriptionName, receiver).build(); } ``` I've configured my Pub/Sub with settings for acknowledgment deadlines and automatic retries, but I'm not seeing the behavior I expected. For instance, if my `processMessage` method throws an exception, I want to ensure that the message gets retried, but I also want to prevent it from being processed multiple times in case of rapid retries. I tried implementing idempotency by maintaining a state in my database, marking messages as processed after successful handling. However, it seems like I'm working with the following scenario: sometimes, messages are being retried multiple times even after successful processing. The behavior logs also show a lot of messages being delivered multiple times, which makes it hard to maintain data integrity. I'm using Spring Cloud GCP version 1.2.2 and have set the acknowledgment deadline to 10 seconds. Is there a recommended pattern for handling retries in GCP Pub/Sub when using Spring Boot? How can I ensure that messages are processed exactly once? Any suggestions or best practices would be greatly appreciated.