如何在Rails中获取一个IP地址?

I have a rails project. I scaffolded Site and Server, their models are below. When a new site is created I want to associate it with the right server by fetching the IP that the url points to. I will run a cronjob or EventMachine to check if this data is still up to date. This way this data will stay up to date and users don't have to maintain it.I have a rails project. I scaffolded Site and S