SNS delivery failures.

SNS (Amazon Simple Notification Service) delivery failures can occur for various reasons. Addressing these issues promptly is important for ensuring reliable message delivery. Here are common causes and steps to address SNS delivery failures:

1. Invalid Endpoint:
   • Cause: The endpoint (e.g., email address, mobile device) subscribed to the topic is incorrect or no longer valid.
   • Solution:
     • Verify that the endpoint is correct and active. If it's no longer valid, you may need to update or remove the subscription.
2. Endpoint Unreachable:
   • Cause: The endpoint (e.g., HTTP/HTTPS endpoint) is temporarily down or experiencing connectivity issues.
   • Solution:
     • Check the status of the endpoint and address any connectivity issues. Consider implementing retries for HTTP/HTTPS endpoints.
3. Invalid Protocol:
   • Cause: The protocol used for the subscription (e.g., SMS, email, HTTPS) is not supported by the endpoint.
   • Solution:
     • Confirm that the protocol chosen is appropriate for the endpoint. For example, an email endpoint should use the "email" protocol.
4. Unsubscribed Endpoint:
   • Cause: The endpoint may have been unsubscribed from the topic.
   • Solution:
     • Verify that the endpoint is still subscribed to the topic. If not, re-subscribe the endpoint.
5. Incorrect Topic ARN:
   • Cause: The Topic ARN used in the publish request is incorrect or invalid.
   • Solution:
     • Double-check that the Topic ARN used in the publish request is accurate and correctly formatted.
6. Invalid Message Payload:
   • Cause: The message payload might not conform to the expected format or may be too large.
   • Solution:
     • Ensure that the message payload adheres to the format expected by the recipient. Verify that the message size does not exceed the allowed limits.
7. Permission Issues:
   • Cause: The IAM user or role attempting to publish to the topic lacks the necessary permissions (sns:Publish).
   • Solution:
     • Check the IAM policies associated with the user or role and ensure that it has the required permissions.
8. Rate Limit Exceeded:
   • Cause: You may be trying to publish messages at a rate that exceeds the allowed limits.
   • Solution:
     • Slow down the rate at which you're publishing messages. Consider implementing retries with exponential backoff for failed deliveries.
9. SNS Service Issues:
   • Cause: There may be temporary service issues with the SNS service itself.
   • Solution:
     • Monitor the AWS Service Health Dashboard for any reported issues with the SNS service.
10. Invalid Platform Application ARN:
    • Cause: If you're using SNS for mobile notifications, the Platform Application ARN may be incorrect or invalid.
    • Solution:
      • Verify that the Platform Application ARN used for mobile notifications is accurate.

Remember to always handle failures gracefully in your applications and consider implementing retry mechanisms for message delivery. If you encounter persistent issues, consider reaching out to AWS Support for further assistance.