As reported on labs-l, SuggestBot's (tools.suggestbot) web server fails to be reachable after a period of time. The web service is reported as up and running and is reachable locally, but not from the outside (e.g. http://tools.wmflabs.org/suggestbot/hw.html fails with a 503 service unreachable).
Restarting the web service fixes the problem but only for 20-or-so minutes, after which 503s are reported again.
BTW, I'll post to labs-l to reflect that this ticket has been created.