Tag: unhealthy targets

In this blog, we explore Automatic Target Weights (ATW), which can reduce the number of errors users experience when using web applications. ATW provides the ability to detect and mitigate gray failures for targets behind Application Load Balancers (ALB). A gray failure occurs when an ALB target passes active load balancer health checks, making it look healthy, but still returns errors. This scenario could be caused by many things, including application bugs, a dependency failure, intermittent network packet loss, a cold cache on a newly launched target, CPU overload, and more.

Introduction The Elastic Load Balancing (ELB) service provides you with Amazon CloudWatch metrics (HealthyHostCount and UnhealthyHostCount) to monitor the targets behind your load balancers. Although the unhealthy host count metric gives the aggregate number of failed hosts, there is a common pain point when you create an alarm for unhealthy hosts based on these metrics. […]