When I use CloudWatch alarm to trigger an AutoScaling action, it repeatedly trigger the ASG actions. In other words, a subsequent set of N Alarms with state ALARM will trigger N actions on ASG. This behavior was not observed for a SNS action, instead it's triggering only within the 1st event when the Alarm changes from OK to ALARM. Is it possible achieve the same action behavior on SNS similar to ASG?
1 Answers
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An Amazon CloudWatch alarm will only trigger an Amazon SNS notification when the alarm enters the ALARM state. That is, it triggers only once, and only when moving from something that isn't ALARM into the ALARM state.
The same CloudWatch alarm, however, will continue to trigger an Auto Scaling Policy.
For example, if an alarm is set to trigger when average CPU Utilization is above 80%, then the alarm will continue to trigger the Scaling Policy while the alarm is in the ALARM state. The Scaling Policy also has a warmup period, during which no additional scaling actions will take place (unless multiple steps are defined and another step limit has been breached).
The above behaviours are intentional and cannot be configured differently.
