AWS Route53 子域间歇性关闭

Question

I have a sub-domain setup on Route53 that points at an ALB. If I hit the ALB DNS name directly, the application responds right away. If I hit any of the nodes in the ECS cluster that the ALB fronts, again, response is immediate. But from time to time, if I hit the sub-domain, it'll take a long time to resolve. Also, if I do

host http://<my route53 sub-domain>

I sometimes get

Host <my route53 sub-domain> not found: 3(NXDOMAIN)

I have about a dozen sub-domains setup just like this (pointing at different ALBs) and haven't had this issue before, except for this most recent micro service.

Question: Where should I look to figure out what could be going on?

Answer 1

I would carefully check the name server configuration. If one is somehow misconfgured, it can cause intermittent issues where some DNS lookups on a single name server fail while others are ok.

Also try a DNS propagation test, to see if your DNS is being propagated properly across the internet. See https://dnsmap.io/ or https://www.whatsmydns.net/ Some problems can be traced that way.

To exclude any issues with your ISPs DNS, try to use a DNS lookups gateway like kloth.net and see if repeated lookups there show the same issue. See http://www.kloth.net/services/nslookup.php

Always use a general DNS checker like https://mxtoolbox.com/dnscheck.aspx to do a complete test of the DNS setup for your domain.