[jbeynon]

If a Heroku application's DNS is setup correctly then you can usually avoid problems like this on the new Heroku stack (CEDAR). It's important to reread the documentation on using custom domains but also be VERY aware of using naked domains (mysite.com) in your application. This isn't just a Heroku problem, it's a DNS problem. Heroku have recently had a spate of routing issues (usually DDoS attacks) which would have been largely negated by correct DNS setup and either avoiding naked domains or using a DNS host that lets you cname a naked domain to a host.

[kilburn]

Could you please elaborate on why exactly using (non-CNAMEd) "naked domains" is a problem? What do "naked domains" and DDoS attacks have to do with each other?

[glenngillen]

DNS only allows you to put an IP addresses on the apex (read: bare/naked/etc) domain A record. That means in the case of a DDoS or other problem affecting one of those IPs you run the risk of having degraded redundancy. Some people unfortunately only put one IP in, which means you're only one machine away from going offline. A long way from what you'd want from the cloud.

DNSimple have created an ALIAS record type which gets around this problem nicely, and Route 53 from Amazon takes a similar approach.