Load balance on URL

[geofft]

We currently source-hash connections; different subsets of the IP space see different servers. While this solves most of the session issues,

1) it becomes really confusing to tell if a site works or not if one server goes wonky, since some people will consistently claim worksforme 2) shared state becomes hard 3) all servers can go down because of one Slashdotted web site

Relatedly, there's no way to visit a particular server or even scripts-test except with old-style URLs, or worse, /etc/hosts hacking.

If, instead of LVS, we set up a proxy that waits until the Host: header or an SNI message to pick a back-end server and forward the connection on, we can load-balance based on locker (determined from the hostname). If we're clever about SSH, we can even load-balance cron and SSH and have users go to "their" server. Then, we can also let people go to ​http://locker.scripts1.scripts.mit.edu, ​http://locker.test.scripts.mit.edu, etc.

[geofft]

Notify 680665 when we do this.