We have 1 sqs that is being consumed by a lambda and we would like to know if all messages in the sqs have been consumed or not after a certain timestamp.
For example, Some other system will start sending messages to the SQS start from 6AM and it will take 4 hours for the lambda to process them all. We would like to know at 10AM, have all messages in the queue been consumed or not.
And we only need to detect the depth of the sqs once every day.
Is there a easy way to setup the alarm in cloudwatch to achieve our use case?
There are many potential solutions such as use cloudwatch rule to trigger a lambda and detect the size of queue and send metric. We can alarm on the metric, but this seems to be heavy lifting
Continual checking
You can create an Amazon CloudWatch alarm on the ApproximateNumberOfMessagesVisible metric for the queue.
For example, if you wish to be notified when the queue has not been empty over the past hour, you can create an alarm when the Min of ApproximateNumberOfMessagesVisible > 0 for 60 minutes. This is saying that the smallest number of messages in the queue for the past hour was above zero.
Checking at a specific time
If you want to check the queue length at a particular time, you will need to use Amazon CloudWatch Events to trigger an AWS Lambda function at a given time.
The Lambda function can call get_queue_attributes() to retrieve ApproximateNumberOfMessages. If this is bigger than desired, the Lambda function could send a message to an Amazon SNS topic. Users can subscribe to the topic to receive an email or SMS notification.