Herokuでこの間発生したHTTPおよびGit接続ができない障害について詳細報告が出た。

• HTTP and Git Connectivity Problems

Root domains are aesthetically pleasing, but the nature of DNS prevents them from being a robust solution for web apps. Root domains don't allow CNAMEs, which requires hardcoding IP addresses, which in turn prevents flexibility on updates to IPs which may need to change over time to handle new load or divert denial-of-service attacks.

We strongly recommend against using root domains. Use a subdomain that can be CNAME aliased to proxy.heroku.com, and avoid ever manually entering IPs into your DNS configuration. We also recommend a low TTL value, which will allow Heroku network engineers to quickly make changes to DNS mapping when necessary.

今回のようなケースで、迅速にconnectivityが復活するようにするには、example.comのようなルートドメインをHerokuのIPアドレスに向けるような設定・運用は避けて、サブドメインがproxy.heroku.comを指すようCNAMEを設定するほうがいいみたい。