// updateReplicaCount attempts to update the Status.Replicas of the given controller, with a single GET/PUT retry. func updateReplicaCount(rcClient client.ReplicationControllerInterface, controller api.ReplicationController, numReplicas int) (updateErr error) { // This is the steady state. It happens when the rc doesn't have any expectations, since // we do a periodic relist every 30s. If the generations differ but the replicas are // the same, a caller might've resized to the same replica count. if controller.Status.Replicas == numReplicas && controller.Generation == controller.Status.ObservedGeneration { return nil } // Save the generation number we acted on, otherwise we might wrongfully indicate // that we've seen a spec update when we retry. // TODO: This can clobber an update if we allow multiple agents to write to the // same status. generation := controller.Generation var getErr error for i, rc := 0, &controller; ; i++ { glog.V(4).Infof("Updating replica count for rc: %v, %d->%d (need %d), sequence No: %v->%v", controller.Name, controller.Status.Replicas, numReplicas, controller.Spec.Replicas, controller.Status.ObservedGeneration, generation) rc.Status = api.ReplicationControllerStatus{Replicas: numReplicas, ObservedGeneration: generation} _, updateErr = rcClient.UpdateStatus(rc) if updateErr == nil || i >= statusUpdateRetries { return updateErr } // Update the controller with the latest resource version for the next poll if rc, getErr = rcClient.Get(controller.Name); getErr != nil { // If the GET fails we can't trust status.Replicas anymore. This error // is bound to be more interesting than the update failure. return getErr } } }