Get a listing of all workers.

        This returns a dictionary mapping worker ID to the mode
        constant for their last observed mode.

        :param bool alive: if true (default), only include workers
          that have called :meth:`Worker.heartbeat` sufficiently recently

def workers(self, alive=True):
        '''Get a listing of all workers.

        This returns a dictionary mapping worker ID to the mode
        constant for their last observed mode.

        :param bool alive: if true (default), only include workers
          that have called :meth:`Worker.heartbeat` sufficiently recently

        '''
        return self.registry.filter(
            WORKER_OBSERVED_MODE,
            priority_min=alive and time.time() or '-inf')