Node.js 0.12.0 had a bug in it whereby sockets that free up due to an error don't handle properly, meaning that an error handler that had been in previous versions wasn't firing. As a result, the socket wasn't completely freed and over time, if enough volume came through, sockets could pile up since we had keep alive enabled. The solution was to change a setting in the Https Agent so that keep alive have shorter timeouts. The better solution is to upgrade to 0.12.1 which we will do sometime soon.