CloudFront Weighted R53 Registers don't work as expected

Hey there,

I see that you are trying to equally distribute traffic between your two alias's using weighted records.

To assist with further investigation of this issue, please confirm the following:

1. How was this record configured before the weighted routing? Was it initially pointing the distribution that the clients are connecting to?
2. Are There any Health Checks on the record ? As it would affect the split of traffic.

A possible cause of this issue may be caching on the client side. Meaning that if the record was using a single distribution and now a second distribution was added with weight, the DNS cache on the clients side could possibly still be resolving to the original distribution that was initially in place.

With that being said I suggest that you to try resolving from a new client and see which IP you get, or try to Flush the DNS cache and then confirm if the issue persists.

As per AWS documentation, it mentions that if you set 0 as the weight for all weighted records then it will route traffic to all. Furthermore, having R53 Health Checks would make that case different [1]. Therefore, I would also suggest setting all weighted to 0 for even distribution and confirm if the issue persists

References: [1] https://docs.aws.amazon.com/Route53/latest/DeveloperGuide/resource-record-sets-values-weighted-alias.html

Route 53 weighted routing does distribute traffic equally when weights are same. However, it doesn't switch traffic between 2 values in a round robin fashion. You can see equal distribution when sample set is large(>1000 queries) and there is no caching at the intermediate resolver.

To test it , send 1000 queries to the domain's authoritative nameservers using the below commands. Hitting authoritative nameservers directly will eliminate the scope of caching at the intermediate resolver.

#!/bin/bash for i in {1..10000} do domain=$(dig <domain-name> <type> @AuthoritativeNameserver_IP +short) echo -e "$domain" >> AuthoritativeNameServer_results.txt done

Reference: https://repost.aws/knowledge-center/route-53-fix-dns-weighted-routing-issue