In parallel.controller.hub, the registration_timeout is set to max(5000, 2*self.heartmonitor.period) and must be an integer, but self.heartmonitor.period is a float.
So, when the period is more than 2500 (doesn't happen with the default value of 1000; only with user-modified values that are higher), a validation error occurs and the hub doesn't start.
@minrk, a simple int(...) around that should do the trick, no?
Indeed, that would fix it, though there's no reason the two shouldn't be the same type. Since these are millisecond times, I will make them both Integer (sub millisecond precision makes no sense).
PR #1283 issues making HeartMonitor.period an integer.