Route 53 ALB Alias Record Health Checks
I have redundant records in a Route 53 configured as alias records to different ALBs, for region-based routing and failover in case of an outage in one region. I have "Evaluate Target Health" enabled on the records. I don't have a custom health check resource associated with records, because according to the documentation:
If you're using alias records to route traffic to selected AWS resources, such as ELB load balancers, you can configure Route 53 to evaluate the health of the resource and to route traffic only to resources that are healthy. When you configure an alias record to evaluate the health of a resource, you don't need to create a health check for the resource.
This what the record configuration looks like in the Route 53 console:
My question is two-fold:
- What exactly are the criteria for an ALB to be considered unhealthy? Is it related to to the health of associated target groups? If so, how does it work for ALBs with more than one target group?
- Is it possible to view the current health status for a record/ALB?
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Hello.
What exactly are the criteria for an ALB to be considered unhealthy? Is it related to to the health of associated target groups? If so, how does it work for ALBs with more than one target group?
We determine whether it is normal by checking the health of the target group linked to the ALB.
Also, if multiple target groups are configured, all target groups will be used to determine health.
https://repost.aws/knowledge-center/load-balancer-marked-unhealthy
When all the target groups in an Application Load Balancer are healthy, Route 53 marks the alias record as "healthy." To pass the target group health check, the number of healthy targets much reach the defined thresholds in your target group attributes. Route 53 then returns records according to your routing policy. For example, if you use latency-based routing, then Route 53 returns the least latent record from your DNS client or resolver's location.
Is it possible to view the current health status for a record/ALB?
Since we are checking the health of the target group, there are probably no metrics for Route53.
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If you use Route 53 to route DNS queries to your load balancer, you can also configure DNS failover for your load balancer using Route 53. In a failover configuration, Route 53 checks the health of the target group targets for the load balancer to determine whether they are available. If there are no healthy targets registered with the load balancer, or if the load balancer itself is unhealthy, Route 53 routes traffic to another available resource, such as a healthy load balancer or a static website in Amazon S3.