So after I got my new server online, I wanted to deal with my oversight on DSN TTLs. Not surprisingly, mod_rewrite saved the day again. First, since my old server is subject to the same TTLs, I added a record in my /etc/hosts file to point all of them at the new IP. Then I changed my Apache config to run this rule set for all hosts:
RewriteEngine On
RewriteCond %{HTTP_HOST} (.+)
RewriteRule ^/(.*)$ http://%1/$1 [P,L]
Done. That simply proxies any request with a host header through to the same exact URL, except that this time the DNS lookup is done by the old server, which has the /etc/hosts file to help it find the right place, instead of the browser that has incorrect DNS cache. Works like a champ.
Barney, this is brilliant, and yet so simple! The DNS has always been the one thing that I felt I had virtually no control over when cutting over a server. This nice little trick gives you the power to make an *instant* controlled cut-over. I can't wait to cut a site over to a new server now ;-)
Thanks once again, as I just found my way back to this post :) I used this trick in an inverse fashion… A friend wanted to move their WordPress sites away from GoDaddy shared hosting to a VPS. I have the virtual host on the new VPS server proxy to the old/current shared hosting and pointed the DNS to the new box. Once DNS has had a fair amount of time to propagate, I can cut-over by setting the doc root instead of proxy to old server. This is necessary because I don't have permission to proxy from GoDaddy shared hosting (at least I assume, but could have tried it from .htaccess, but doubt they'd allow open proxies by shared hosting customers). Cheers.