Naftuli.wtf Website Review

Opinions expressed here do not reflect those of previous or current employer(s). This is based on a real environment that I worked with, the names have been changed to protect the guilty. In a nutshell, there was a VPC in Amazon in us-east-1, a VPC in Amazon in us-west-2, and a datacenter somewhere in between. The VPCs in Amazon could not talk to each other, but could each communicate with the datacenter. The web applications in the diagram all ran the same cluster across the continental US, but this isn’t a contrived example: this was something we had to support. In order for the VPCs to resolve the IP addresses of the MySQL cluster, we injected the IP addresses for ns1 and ns2 into Amazon’s DHCP option set, yielding three resolvers: our two resolvers and the Amazon provided DNS resolver. After vigorous testing, we brought us-east-1 online to begin serving traffic, using a CDN to geographically route to the nearest set of servers. Almost immediately, our average request time skyrocketed. We immediately suspected that this was related to MySQL, but after a lot If you’ve been in the industry long enough, this haiku will strike home and strike hard. coast about that. Where can I find east.mycompany.com? Here, lemme ask the west coast about that. Not only would it cross the US once, for This was bad. However, a quick web search for “dns caching resolver” brought up dnsmasq. What we subsequently did was to The first order of business was to figure out a way to prepend 127.0.0.1 as the first resolver is the basic premise of DNS: things change, but to make things more efficient, cache them as long as they are to be considered valid. Just like your CDN should be caching your as*ets for as long as it is reasonable to do so, DNS entries should be cached as long as they are Unfortunately, as in the haiku above, almost everything seems to get DNS wrong. It either doesn’t cache at all, or permanently caches Therefore it’s either surprising or entirely not surprising that gethostname(3) makes no effort to cache values, making things very