A SysOps administrator is managing a web application that runs on Amazon EC2 instances behind an Application Load Balancer (ALB).The instances run in an EC2 Auto Scaling group.The administrator wants to set an alarm for when all target instances associated with the ALB are unhealthy.
Which condition should be used with the alarm?
AWS/ApplicationELB HealthyHostCount <= 0
AWS/ApplicationELB UnhealthyHostCount >= 1
AWS/EC2 StatusCheckFailed <= 0
AWS/EC2 StatusCheckFailed >= 1
Explanations:
TheAWS/ApplicationELB HealthyHostCount <= 0condition will trigger the alarm when all target instances behind the ALB are unhealthy, as the count of healthy instances is zero.
AWS/ApplicationELB UnhealthyHostCount >= 1only indicates at least one instance is unhealthy, not all instances.
AWS/EC2 StatusCheckFailed <= 0does not monitor ALB target health but EC2 instance health checks.
AWS/EC2 StatusCheckFailed >= 1also checks EC2 instance status, not ALB target health, which is not suitable here.
I calculate that the answer is:
AWS/ApplicationELB HealthyHostCount