Change:
<ins> /* Copyright 2016 The Kubernetes Authors. Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. */ package util import ( "fmt" "time" federation_release_1_4 "k8s.io/kubernetes/federation/client/clientset_generated/federation_release_1_4" pkg_runtime "k8s.io/kubernetes/pkg/runtime" ) // Type of the operation that can be executed in Federated. type FederatedOperationType string const ( OperationTypeAdd    = "add" OperationTypeUpdate = "update" OperationTypeDelete = "delete" ) // FederatedOperation definition contains type (add/update/delete) and the object itself. type FederatedOperation struct { Type FederatedOperationType Obj  pkg_runtime.Object } // A helper that executes the given set of updates on federation, in parallel. type FederatedUpdater interface { // Executes the given set of operations within the specified timeout. // Timeout is best-effort. There is no guarantee that the underlying operations are // stopped when it is reached. However the function will return after the timeout // with a non-nil error. Update([]FederatedOperation, time.Duration) error } // A function that executes some operation using the passed client and object. type FederatedOperationHandler func(federation_release_1_4.Interface, pkg_runtime.Object) error type federatedUpdaterImpl struct { federation FederationView addFunction    FederatedOperationHandler updateFunction FederatedOperationHandler deleteFunction FederatedOperationHandler } func NewFederatedUpdater(federation FederationView, add, update, del FederatedOperationHandler) FederatedUpdater { return &federatedUpdaterImpl{ federation:     federation, addFunction:    add, updateFunction: update, deleteFunction: del, } } func (fu *federatedUpdaterImpl) Update(ops []FederatedOperation, timeout time.Duration) error { done := make(chan error, len(ops)) for _, op := range ops { go func(op FederatedOperation) { clusterName, err := GetClusterName(op.Obj) if err != nil { done <- err return } // TODO: Ensure that the clientset has reasonable timeout. clientset, err := fu.federation.GetClientsetForCluster(clusterName) if err != nil { done <- err return } switch op.Type { case OperationTypeAdd: err = fu.addFunction(clientset, op.Obj) case OperationTypeUpdate: err = fu.updateFunction(clientset, op.Obj) case OperationTypeDelete: err = fu.deleteFunction(clientset, op.Obj) } done <- err }(op) } start := time.Now() for i := 0; i < len(ops); i++ { now := time.Now() if !now.Before(start.Add(timeout)) { return fmt.Errorf("failed to finish all operations in %v", timeout) } select { case err := <-done: if err != nil { return err } case <-time.After(start.Add(timeout).Sub(now)): return fmt.Errorf("failed to finish all operations in %v", timeout) } } // All operations finished in time. return nil } </ins>

Discussion:
Federated controllers will oftentimes have to crreate/update/delete the same/similar structures in multiple clusters. Given that the roundtrip time to remote clusters can be high (like, lets say, 1 sec) these operations should be done in parallel so that the main controller goroutine is not blocked for long. Part of