When the hub is running in API-only mode, it's
very useful to have the proxy know where to send
URLs that would normally be serviced by the hub.
For example, / might go to a service that renders
a home page, while `/user` might go to a service that
tells the user their server is dead.
Right now, this happens 'out of band', with a process
that has to talk to the proxy directly. This is a
bit messy - the routes need to be re-added when the
proxy restarts, the hub might try to remove them, etc.
By adding support for this in the hub itself, all
this complexity is now removed and the hub continues
to own all the routes in the proxy
this is the routespec for sending requests to the hub
It is [host]/prefix/ (not /hub/) so it receives all
requests, not just those destined for the hub
.terminate() only sends the signal,
it doesn't wait for the process to exit.
If the process doesn't exit promptly,
the next instance may try to grab the port before the previous process has released it,
causing failure with EADDRINUSE.
it was made a method for handing named_servers,
but that made things way more complicated and replaced a boolean flag with a callable,
which would behave unexpectedly but without error if a boolean flag was expected.
Spawners have properties for dealing with this now, so use spawners
Restore `user.running` as an alias for `user.spawner.ready`
prevent `.check_routes` from firing while we wait for a new proxy to come up
We check explicitly that it comes up with no routes, so makes sure check_routes hasn't restored its state, which is causing intermittent failures
namedtuple(path, host)
everywhere that accepts a RouteSpec must also accept a string
and treat it as RouteSpec(string).
RouteSpec.as_routespec(spec_or_string) handles this.
