ELB Health Checks
Health checks in Elastic Load Balancing are a feature that continuously monitors the health of the registered instances, marking them as healthy or unhealthy based on predefined criteria. They are used to determine which instances can receive traffic from the load balancer. Health checks are configured to evaluate the response of an HTTP or TCP request sent to a specified port on the instance, determining the instance's health status. Unhealthy instances are removed from the load balancer until they return as healthy, ensuring that the load balancer always routes traffic to healthy instances.
Guide to ELB Health Checks in AWS Solution Architect
The examination of AWS Solution Architect involves a wide range of concepts including Elastic Load Balancing and its associated ELB Health Checks.
What is ELB Health Checks?
ELB Health Checks is a functionality provided by AWS within Elastic Load Balancer (ELB) that ensures efficient routing of network traffic based on the health and availability of the registered targets.
Why ELB Health Checks is Important?
The primary importance of ELB Health checks lies in its ability to continuously monitor the health of applications and routes network traffic only to healthy resources, thus ensuring optimal performance and availability.
How does ELB Health Checks work?
Heathy checks function by periodically sending ping, connection or custom health check requests to the target. Based on the response, it categorizes targets as healthy or unhealthy. It then only routes the traffic to those instances marked as healthy. Unhealthy instances are isolated until they are healthy again.
Exam Tips: Answering Questions on ELB Health Checks
When answering questions related to ELB Health Checks:
1. It's important to understand the mechanism of health checks in ELB.
2. Be aware that unhealthy instances are automatically deregistered and do not receive network traffic.
3. ELB Health checks can be customized, understand how this works as it may come up in exam scenarios.
4. Note that successful health checks do not necessarily mean your application is responding correctly to requests, it merely indicates the target instance is reachable.
5. Remember that health check is a two-way strategy - it not only verifies instance health but also helps to maintain a high level of application availability by routing requests to healthy instances.
AWS Certified Solutions Architect - Elastic Load Balancing (ELB) Example Questions
Test your knowledge of Amazon Simple Storage Service (S3)
Question 1
A network load balancer must distribute incoming traffic to an application composed of multiple EC2 instances. The application must maintain stable performance regardless of changes in workload. What health check change ensures the best performance?
Question 2
An application receives a large number of TCP connections. Users report intermittent failed connections. How can you configure the health checks to address this problem?
Question 3
A web application with an ELB receives sudden spikes of traffic. Users report slow performance during these spikes. You've been asked to improve the health checks so unhealthy instances are quickly removed from the ELB. What is the best configuration change you can make?
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