云 DNS：健康检查？

Question

Does GCP's Cloud DNS have health check functionality? For example, if I am using a weighted round robin policy, or if I am returning multiple A records, then I do not want Cloud DNS to return an unhealthy IP in its answer. These IPs will be individual servers, not Load Balancer IPs, so it is entirely possible that an individual IP could become unhealthy.

In AWS, their equivalent Route53 product does offer that functionality ( reference ). I want to know if GCP's Cloud DNS has something similar.

Answer 1

Currently there is no such option.
You can point A record to a loadbalancer's IP and configure health checks on that level ( 1 ).
You can also file a Feature Request on the Public Issue Tracker .

Answer 2

Although I like the features that Route 53 offers, DNS is the wrong place to do health checks.

DNS resource records are cached globally which renders Route 53 health check nondeterministic.

DNS resource records have a TTL. Resolvers will continue to use cached values until the TTL expires. If one of your nodes fails, the cache records will not reflect Route 53's updates.

Some configure very short TTLs to get around that. The tradeoff is slower DNS response time, and higher query costs.

Recommendation, use a load balancer and its health checks which understand the protocols required.

Answer 3

GCP Cloud DNS health checks arein preview now.

Only internal L4 load balancers are supported yet. Hopefully, L7s will come in soon as well.

Answer 4

If I understand correctly, with LB level health checks I could resolve the situation for just backends on GCP, but what if I have a hybrid scenario, with VMs on GCP + VMs on-premises?

How could I fail over DNS, from on-premises to GCP backends, to a disaster recovery solution (for example), assuming that Google CloudDNS is my Public DNS resolver?