We just had a complete Koha outage which we believe was caused by 150+ requests to /cgi-bin/koha/circ/returns.pl sent simultaneously. Apparently this could have been caused by someone on the issue desk accidentally pressing the resend key. Our server support people have to kill the processes, presumably via the command line. It would be very easy to trigger repeated calls to returns.pl (and I guess other scripts) by accidently resting a book (or whatever) on the edge of the keyboard, catching the Enter key. Just now I was able to bring down our test system (both intranet and OPAC) by merely holding down the enter key (using returns.pl) for maybe a maximum of 5-7 seconds. This a serious vulnerability, where a momentary lapse of care with a book on a keyboard can crash the Koha system. Ray Delahunty University of the Arts London
This may have been due in part to us having an underpowered Koha server. Apparently there is a firewall rule that should stop more than 200 requests from a single IP being accepted. I was running a 5,000 record import at the same time the keyboard key was left depressed, and the suggestion is that the load on the server from this import was high, and the c.150 simultaneous requests (below the 200 threshold) was enough to crash the server. We are upgrading the server within the next 24 hours, including adding a second processor. Ray Delahunty University of the Arts London
I think overall this sounds more like a system administration/hardware issue. So something that should likely be solved outside of Koha. Please re-open if you disagree.