I suppose it was only a matter of time, but the bad web robot behavior has finally reached Gemini. There's a bot out there that made 42,766 requests in the past 27 hours (so not quite one-per-second) until I got fed up with it and blocked it at the firewall. And according to my firewall, it's still trying to make requests. That tells me that whatever it is, it's running unattended. And several other people running Gemini servers have reported seeing the same client hammering their systems as well.
Now, while the requests average out to about one every two seconds, they actually come in bursts—a metric buttload pops in, a bunch fail to connect (probably because of some kernel limit) and all goes quiet for maybe half a minute before it starts up again. Had it actually limited the requests to one every two seconds (or even one per second) I probably wouldn't mind as much.
As it was though, quite a large number of the requests were malformed—it wasn't handling relative links properly, so I can only conclude it was written by the same set of geniuses that wrote the MJ12Bot.
On the plus side, it did reveal a small bug in the codebase, allowing some of the malformed requests to be successful when they shouldn't have been.