AWS Lamba constantly receiving empty SQS event messages

Question

I'm a relative n00b at AWS, so apologise if this is a stupid question.

I have an AWS Lambda written in Java. I also have an SQS queue that receives AWS S3 event messages. I've then created a Lambda trigger against the SQS queue so that my Lambda receives the S3 events as SQS messages and processes them appropriately.

It all works well. The only issue I have is that it seems like the Lambda is receiving notification of an SQS event message every 2 minutes, even when there are no messages in the SQS queue.

The Java code looks like this:

public class SQSEventHandler implements RequestHandler<SQSEvent, Void> {
    @Override
    public Void handleRequest(SQSEvent sqsEvent, Context context) {
        if (sqsEvent != null) {
            LOGGER.debug("Received SQS event: {}", sqsEvent.toString());
            ... do stuff...

If I look in the CloudWatch logs (I log using SLF4J), I can see that the Lambda is triggered with different SQS messages every 2 minutes, even during periods when there are no S3 event messages to process:

02:54:16 START RequestId: d5454080-8ea3-4c44-93e9-caa5bd903599 Version: $LATEST
02:54:16 [2020-02-13 02:54:16.220] - [d5454080-8ea3-4c44-93e9-caa5bd903599] DEBUG <package>.SQSEventHandler - Received SQS event: {}
02:54:16 END RequestId: d5454080-8ea3-4c44-93e9-caa5bd903599
02:54:16 REPORT RequestId: d5454080-8ea3-4c44-93e9-caa5bd903599 Duration: 1.05 ms Billed Duration: 100 ms Memory Size: 512 MB Max Memory Used: 161 MB
02:56:16 START RequestId: 9d5acbba-b96c-47e9-81c2-2d448e4ca6e9 Version: $LATEST
02:56:16 [2020-02-13 02:56:16.386] - [9d5acbba-b96c-47e9-81c2-2d448e4ca6e9] DEBUG <package>.SQSEventHandler - Received SQS event: {}
02:56:16 END RequestId: 9d5acbba-b96c-47e9-81c2-2d448e4ca6e9
02:56:16 REPORT RequestId: 9d5acbba-b96c-47e9-81c2-2d448e4ca6e9 Duration: 1.23 ms Billed Duration: 100 ms Memory Size: 512 MB Max Memory Used: 161 MB
02:58:16 START RequestId: 54bc4fa4-bcaf-4834-9185-09c9c7e2d757 Version: $LATEST
02:58:16 [2020-02-13 02:58:16.451] - [54bc4fa4-bcaf-4834-9185-09c9c7e2d757] DEBUG <package>.SQSEventHandler - Received SQS event: {}
02:58:16 END RequestId: 54bc4fa4-bcaf-4834-9185-09c9c7e2d757
02:58:16 REPORT RequestId: 54bc4fa4-bcaf-4834-9185-09c9c7e2d757 Duration: 1.01 ms Billed Duration: 100 ms Memory Size: 512 MB Max Memory Used: 161 MB

There are no other SQS queues with triggers to this Lambda.

As you can see, the SQS event object isn't null but doesn't produce anything in the toString() call.

I can't work out what the issue is - any assistance would be appreciated.

GarlicBread GarlicBread · Accepted Answer · 2020-02-13T20:32:17

Unbeknownst to me, there was a CloudWatch rule set up to send a message to my Lambda every two minutes. Once this had been located, I disabled the rule and the Lambda was no longer triggered.

AWS Lamba constantly receiving empty SQS event messages

2 Answers