Does ':flush-all-connection-in-pool' do what you need? MIght be that you have to set min-pool-size=0 if you don't want to have openen connections after that, but this is also a attribute with reload-required.
Yes, thanks, I think that will do. For some reason I managed to get a "success" without reload for setting both the min and max pool size. Not that it prevented connections from appearing after the flush, though. Hopefully, the filter should kick people out on next request before any more connection can be created...