evaluateTargetHealth

Applies only to alias, failover alias, geolocation alias, latency alias, and weighted alias resource record sets: When EvaluateTargetHealth is true, an alias resource record set inherits the health of the referenced Amazon Web Services resource, such as an ELB load balancer or another resource record set in the hosted zone.

Note the following:

CloudFront distributions

You can't set EvaluateTargetHealth to true when the alias target is a CloudFront distribution.

Elastic Beanstalk environments that have regionalized subdomains

If you specify an Elastic Beanstalk environment in DNSName and the environment contains an ELB load balancer, Elastic Load Balancing routes queries only to the healthy Amazon EC2 instances that are registered with the load balancer. (An environment automatically contains an ELB load balancer if it includes more than one Amazon EC2 instance.) If you set EvaluateTargetHealth to true and either no Amazon EC2 instances are healthy or the load balancer itself is unhealthy, Route 53 routes queries to other available resources that are healthy, if any.

If the environment contains a single Amazon EC2 instance, there are no special requirements.

ELB load balancers

Health checking behavior depends on the type of load balancer:

• Classic Load Balancers: If you specify an ELB Classic Load Balancer in DNSName, Elastic Load Balancing routes queries only to the healthy Amazon EC2 instances that are registered with the load balancer. If you set EvaluateTargetHealth to true and either no EC2 instances are healthy or the load balancer itself is unhealthy, Route 53 routes queries to other resources.

• Application and Network Load Balancers: If you specify an ELB Application or Network Load Balancer and you set EvaluateTargetHealth to true, Route 53 routes queries to the load balancer based on the health of the target groups that are associated with the load balancer:

  • For an Application or Network Load Balancer to be considered healthy, every target group that contains targets must contain at least one healthy target. If any target group contains only unhealthy targets, the load balancer is considered unhealthy, and Route 53 routes queries to other resources.

  • A target group that has no registered targets is considered unhealthy.

When you create a load balancer, you configure settings for Elastic Load Balancing health checks; they're not Route 53 health checks, but they perform a similar function. Do not create Route 53 health checks for the EC2 instances that you register with an ELB load balancer.

S3 buckets

There are no special requirements for setting EvaluateTargetHealth to true when the alias target is an S3 bucket.

Other records in the same hosted zone

If the Amazon Web Services resource that you specify in DNSName is a record or a group of records (for example, a group of weighted records) but is not another alias record, we recommend that you associate a health check with all of the records in the alias target. For more information, see What Happens When You Omit Health Checks? in the Amazon Route 53 Developer Guide.

For more information and examples, see Amazon Route 53 Health Checks and DNS Failover in the Amazon Route 53 Developer Guide.