[🚀Launch Announcement] - Network Load Balancer (NLB) introduces Zonal Health Status CloudWatch Metric

Network Load Balancer (NLB) has introduced a new CloudWatch metric called ZonalHealthStatus, which represents the health status of an NLB in each availability zone (AZ). This new metric provides you more insight into events that cause a fail-away so you can implement preventative and/or reactive measures to ensure optimal application availability.

Today, each AZ of an NLB uses one IP address. Route 53 stores IP addresses of each AZ of NLB in its DNS records and keeps checking health of each zonal NLB. If the NLB fails health check in a particular AZ, the corresponding IP address of the NLB is removed from DNS record on Route 53. With this new metric, you can set up CloudWatch Alarm on the metric to monitor the health of your NLB in all zones. You can also use the metric to quickly identify the zone where the NLB had failed away and IP was temporarily removed due to your load balancer configuration (i.e., your healthy target count in the zone falls below your configured minimum health target threshold), zonal shift, gray failures, or other issues. With this visibility, you can quickly determine the health of your NLB and take appropriate actions, such as provisioning more targets in a particular zone, if needed. You can view the ZonalHealthStatus metric in the CloudWatch Console or add it to the ELB Console Monitoring Dashboard.

This feature is available in all commercial AWS Regions. To learn more, please visit https://docs.aws.amazon.com/elasticloadbalancing/latest/network/network-load-balancers.html#load-balancer-zonal-health.