Domain Name System - the forgotten cloud service

Inspired by the good folks at Rackspace (specifically, this post), I realised how important it was to have a easily programmable DNS api for cloud applications and services.

Why do I need to care about DNS ?

Well, its all very well deploying your fantastic app to a fantastic elastic cluster, but its not so fun when it has urls like

http://somethingwierd.4324324.xyz.zw.com
http://203.143.2.23

(I hope I haven't offended anyone by using those addresses - there was one time Van Halen put a serial number on the back of an album that happened to be someones phone number, so crazed fans called the number, over and over, until Van Halen was sued over it. But I digress). So to avoid being sued due to over zealous Van Halen fans, you need to have a naming service: DNS. The fabric of the internet, full of quaint terms like "bailiwick" (I wish I wasn't making this up). For single apps, you can use either your own DNS server(s), or use a pay for service etc (there are many options of course). Running your own DNS is nice, it gives you flexibility to run many apps under one domain (using subdomains for specific apps), use it to "move" apps around whenever you need (which is pretty common in clouds - servers can come and go, change data centres, change IPs as you bring up a new one etc).

A simple API

Wouldn't it be nice to have some near API to make it as simple as:

curl -d subdomain=applicationName&address=1.2.3.4 http://coolingtower/api/naming/domains/samplezone.org
curl -d subdomain=applicationName&address=somewhere.com http://coolingtower/api/naming/domains/samplezone.org

Well you would be in luck! (It is a nice rule of thumb that a RESTful interface can be driven from the command line - the above using the excellent curl tool - you can use anything of course). However, DNS is full of traps for young players, and really, what we want is to be a big Map<String, IP> in the sky, magically guiding browsers to the right server.

Where and when would I use this?

Mainly for the entry points that end users will see in their browser- but it can also be useful for internal resources like databases, and other services that your applications consume (to avoid binding to IPs directly). For example, imagine you have your own cloud service, you register name for the top level domain: stormgrind.com. With a DNS service you can have:

http://demo.stormgrind.com
http://db1.stormgrind.com
http://www.stormgrind.com

...and so on, you get the idea.

A RESTful API for DNS management

CoolingTower has a programmatic (RESTful) interface to manage DNS mappings, and also an (optional) authoritative DNS server (if you don't have one already). DNS data is stored in standard "zone files". It will validate and store the changes in zone files - and those changes can be propagated to the DNS servers. If you use the EagleDNS service it will instantly pick up the changes and apply them - applying sensible defaults, updating serial numbers, setting short time to live values (so changes are applied quickly) - all are done automatically to keep things easy and less error prone. There is much more to the RESTful api, and it is being documented.

More info and some links

  • CoolingTower naming service documentation/wiki.
  • Build/source install instructions here.
  • EagleDNS is can be obtained from here (the latest release has my patches for automatically updating zones are they are changed).