ELB Health Check Monitoring and Debugging

Grab has evolved its understanding and debugging of Elastic Load Balancer (ELB) health check behavior. This post details an investigation into unexpected increases in health check metrics, which were initially mistaken for new instance scaling. The root cause was identified as the coexistence of old and new ELB nodes during scaling events, leading to a doubling of health checks. This led to a refinement in monitoring practices, separating dependency health checks from ELB health checks and emphasizing the importance of understanding the nuances of ELB behavior during scaling events.