    async def check_services_health(self):
        """Check connectivity of all services"""
        for name, service in self._service_map.items():
            if not service.url:
                # no URL to check, nothing to do
                continue
            try:
                await Server.from_orm(service.orm.server).wait_up(timeout=1, http=True)
            except AnyTimeoutError:
                self.log.warning(
                    "Cannot connect to %s service %s at %s",
                    service.kind,
                    name,
                    service.url,
                )
            else:
                self.log.debug(
                    "%s service %s running at %s",
                    service.kind.title(),
                    name,
                    service.url,
                )
Check connectivity of all services
jupyterhub/app.py