Recently I have configured the ALARM in Cloudwatch for tracking VPN Tunnel connection. It is well known that 0 indicates tunnel is DOWN and 1 indicates tunnel is UP. When Connection is down, I have seen some data points on the graph shown as 0.66, 0.75.
So what does that mean, is the connection is DOWN or UP?
Statistics are metric data aggregations over specified periods of
time. CloudWatch provides statistics based on the metric data points
provided by your custom data or provided by other AWS services to
CloudWatch. Aggregations are made using the namespace, metric name,
dimensions, and the data point unit of measure, within the time period
you specify. The following table describes the available statistics.
Given the VPN metric above, try using the Maximum or Minimum statistics for the alarm. You are using the Average statistic, which, as you noted, will not produce meaningful data for your use case.
The lowest value observed during the specified period. You can use this value to determine low volumes of activity for your application.
The highest value observed during the specified period. You can use this value to determine high volumes of activity for your application.