Question

A SysOps administrator configures a CloudWatch alarm on the RequestCount metric of an Application Load Balancer to detect when a downstream application stops receiving traffic (a value of 0). During periods of very low activity, the ALB publishes no data points for RequestCount at all, and the administrator notices the alarm sits in INSUFFICIENT_DATA instead of alerting on the traffic drop. The alarm must reliably enter the ALARM state and notify an SNS topic when request traffic falls to zero. Which configuration change should the administrator make?

Accepted Answer

Set the alarm's 'Treat missing data as' setting to 'breaching' and configure the threshold to trigger when the value is less than or equal to 0.

Answer

Enable detailed monitoring on the ALB so that RequestCount reports data points every minute even when there is no traffic.

Answer

Configure the alarm's 'Treat missing data as' setting to 'ignore' so the last known state is retained until traffic resumes.

Answer

Increase the alarm evaluation period to 15 minutes so that a data point is guaranteed to be present within each evaluation window.