func (rs *REST) Update(ctx api.Context, obj runtime.Object) (runtime.Object, bool, error) {
	service := obj.(*api.Service)
	if !api.ValidNamespace(ctx, &service.ObjectMeta) {
		return nil, false, errors.NewConflict("service", service.Namespace, fmt.Errorf("Service.Namespace does not match the provided context"))
	}

	oldService, err := rs.registry.GetService(ctx, service.Name)
	if err != nil {
		return nil, false, err
	}

	// Copy over non-user fields
	// TODO: make this a merge function
	if errs := validation.ValidateServiceUpdate(service, oldService); len(errs) > 0 {
		return nil, false, errors.NewInvalid("service", service.Name, errs)
	}

	nodePortOp := portallocator.StartOperation(rs.serviceNodePorts)
	defer nodePortOp.Finish()

	assignNodePorts := shouldAssignNodePorts(service)

	oldNodePorts := CollectServiceNodePorts(oldService)

	newNodePorts := []int{}
	if assignNodePorts {
		for i := range service.Spec.Ports {
			servicePort := &service.Spec.Ports[i]
			nodePort := servicePort.NodePort
			if nodePort != 0 {
				if !contains(oldNodePorts, nodePort) {
					err := nodePortOp.Allocate(nodePort)
					if err != nil {
						el := field.ErrorList{field.Invalid(field.NewPath("spec", "ports").Index(i).Child("nodePort"), nodePort, err.Error())}
						return nil, false, errors.NewInvalid("Service", service.Name, el)
					}
				}
			} else {
				nodePort, err = nodePortOp.AllocateNext()
				if err != nil {
					// TODO: what error should be returned here?  It's not a
					// field-level validation failure (the field is valid), and it's
					// not really an internal error.
					return nil, false, errors.NewInternalError(fmt.Errorf("failed to allocate a nodePort: %v", err))
				}
				servicePort.NodePort = nodePort
			}
			// Detect duplicate node ports; this should have been caught by validation, so we panic
			if contains(newNodePorts, nodePort) {
				panic("duplicate node port")
			}
			newNodePorts = append(newNodePorts, nodePort)
		}
	} else {
		// Validate should have validated that nodePort == 0
	}

	// The comparison loops are O(N^2), but we don't expect N to be huge
	// (there's a hard-limit at 2^16, because they're ports; and even 4 ports would be a lot)
	for _, oldNodePort := range oldNodePorts {
		if !contains(newNodePorts, oldNodePort) {
			continue
		}
		nodePortOp.ReleaseDeferred(oldNodePort)
	}

	// Remove any LoadBalancerStatus now if Type != LoadBalancer;
	// although loadbalancer delete is actually asynchronous, we don't need to expose the user to that complexity.
	if service.Spec.Type != api.ServiceTypeLoadBalancer {
		service.Status.LoadBalancer = api.LoadBalancerStatus{}
	}

	out, err := rs.registry.UpdateService(ctx, service)

	if err == nil {
		el := nodePortOp.Commit()
		if el != nil {
			// problems should be fixed by an eventual reconciliation / restart
			glog.Errorf("error(s) committing NodePorts changes: %v", el)
		}
	}

	return out, false, err
}

func (svcStrategy) ValidateUpdate(ctx api.Context, obj, old runtime.Object) field.ErrorList {
	return validation.ValidateServiceUpdate(obj.(*api.Service), old.(*api.Service))
}