We announced Denominator at our February NetflixOSS meetup, and now we are ready to release the first code as open source. Denominator is a portable Java library for manipulating DNS clouds. Denominator has pluggable back-ends, initially including AWS Route53, Neustar Ultra, DynECT, and a mock for testing. We also ship a command line version so it's easy for anyone to try it out.
The reason we built Denominator is that we are working on multi-region failover and traffic sharing patterns to provide higher availability for the streaming service during regional outages caused by our own bugs and AWS issues. To do this we need to directly control the DNS configuration that routes users to each region and each zone. When we looked at the features and vendors in this space we found that we were already using AWS Route53, which has a nice API but is missing some advanced features; Neustar UltraDNS, which has a SOAP based API; and DynECT, which has a REST API that uses a quite different pseudo-transactional model. We couldn’t find a Java based API that grouped together common set of capabilities that we are interested in, so we created one. The idea is that any feature that is supported by more than one vendor API is the highest common denominator, and that functionality can be switched between vendors as needed, or in the event of a DNS vendor outage.