How Long will an Instance Take to Become Healthy with Elastic Load Balancer Settings?
Question
An Elastic Load balancer has just been setup with the following settings HealthCheck Interval - 5 seconds Healthy threshold -5 UnHealthy threshold -6 How long will an instance take to become healthy with the above settings?
Answers
Explanations
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A. B. C. D.Answer - D.
If the instance checks pass through and the all ELB health pings work, then the Instance would be marked as healthy after HealthCheck Interval* Healthy threshold time interval.
For more information on configuring health checks for the ELB please refer to the below URL:
http://docs.aws.amazon.com/elasticloadbalancing/latest/classic/elb-healthchecks.htmlIn this scenario, the Elastic Load Balancer (ELB) has been configured with the following settings:
- HealthCheck Interval - 5 seconds
- Healthy threshold - 5
- UnHealthy threshold - 6
The health check interval refers to the time interval between two consecutive health checks. In this case, the ELB will check the health of the instances every 5 seconds.
The healthy threshold refers to the number of consecutive successful health checks required to mark an instance as healthy. In this case, an instance needs to pass 5 consecutive health checks to be marked as healthy.
The unhealthy threshold refers to the number of consecutive failed health checks required to mark an instance as unhealthy. In this case, an instance needs to fail 6 consecutive health checks to be marked as unhealthy.
Now, let's consider how long it will take for an instance to become healthy with these settings.
Assuming that the instance is initially marked as unhealthy, the ELB will start performing health checks every 5 seconds. If the first health check is successful, the instance will still be marked as unhealthy since it hasn't reached the healthy threshold of 5 consecutive successful health checks.
If the second health check is successful, the instance will still be marked as unhealthy since it hasn't reached the healthy threshold of 5 consecutive successful health checks.
This process will continue until the instance passes the fifth consecutive health check. At this point, the instance will be marked as healthy.
Therefore, the time it will take for an instance to become healthy with these settings is:
5 seconds (for the first health check) + 20 seconds (for passing 4 more consecutive health checks) = 25 seconds
So the answer is D. 25 seconds.
