each time a new curl object was created, modprobe would spawn, checking net-pf-10 to evaluate IPv6 status.
Linux seems to have a few “touch the network stack and magic will happen” edges. This automatism of kernel module loading vaguely reminded me of this: http://backstage.soundcloud.com/2012/08/shoot-yourself-in-the-foot-with-iptables-and-kmod-auto-loading/
I might be wrong, but this probably has something to do with automatic kernel module loading. Although I have no idea why they had that enabled on a production server. Perhaps the OS had it enabled by default and they didn’t realize.
This might refer to pycurl’s Curl objects (assuming that bitly uses python as the rest of their blog seems to suggest content-wise).
10 Things Bitly Should Have Monitored – http://highscalability.com/blog/2014/1/29/10-things-bitly-should-have-monitored.html