amazon-web-servicescloudwatch-alarms

AWS alarm goes to Ok state unexpectedly

I have an alarm setup in AWS cloudwatch which generates a data point every hour. When its value is greater than or equal to 1, it goes to ALARM state. Following are the settings

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On 2nd Nov, it got into ALARM state and then back to OK state in 3 hours. I'm just trying to understand why it took 3 hours to get back to the OK state instead of 1 hour because the metric run every hour.

Here's are the logs which prove that metric transited from ALARM to OK state in 3 hours.

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Following is the graph which shows the data point value every hour.

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Solution

  • This is probably because alarms are evaluated on longer period then your 1 hour. The period is evaluation range. In your case, the evaluation range could be longer then your 1 hour, thus it takes longer for it to change.

    There is also thread about this behavior with extra info on AWS forum:

    . Unexplainable delay between Alarm data breach and Alarm state change