AWS Lambda function was trigger twice by CloudWatch event

Question

I deployed a service written in Python2.7 using AWS Lambda, and it's about extracting data from some pages and sending results to a web app. The service is triggered by the AWS CloudWatch event (fixed rate of 5 mins).

However, I found out sometimes the service was triggered twice at a time. I got this because there were two log stream printed the same data and result but with different RequestID's. And the database had duplicate data, which showed that both worked successfully. It looked like the service was triggered twice almost at the same time for no reasons.

Does anyone experience the same thing, and how do you fix it? Or, is there a way to limit only one function can be executed at a time.

Answer 1

Yes. Some AWS services have SLA of at least once delivery. I have experienced this with CloudWatch and CloudTrail. I do not know if you can limit it only once. You have to check if the data has been processed already. I overcame this by making boto3 calls in my python code before processing the data. Without knowing your situation, it is difficult to suggest a solution.