diff --git a/tools/watch/until.go b/tools/watch/until.go new file mode 100644 index 00000000..c2772ddb --- /dev/null +++ b/tools/watch/until.go @@ -0,0 +1,87 @@ +/* +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 watch + +import ( + "errors" + "time" + + "k8s.io/apimachinery/pkg/util/wait" +) + +// ConditionFunc returns true if the condition has been reached, false if it has not been reached yet, +// or an error if the condition cannot be checked and should terminate. In general, it is better to define +// level driven conditions over edge driven conditions (pod has ready=true, vs pod modified and ready changed +// from false to true). +type ConditionFunc func(event Event) (bool, error) + +// ErrWatchClosed is returned when the watch channel is closed before timeout in Until. +var ErrWatchClosed = errors.New("watch closed before Until timeout") + +// Until reads items from the watch until each provided condition succeeds, and then returns the last watch +// encountered. The first condition that returns an error terminates the watch (and the event is also returned). +// If no event has been received, the returned event will be nil. +// Conditions are satisfied sequentially so as to provide a useful primitive for higher level composition. +// A zero timeout means to wait forever. +func Until(timeout time.Duration, watcher Interface, conditions ...ConditionFunc) (*Event, error) { + ch := watcher.ResultChan() + defer watcher.Stop() + var after <-chan time.Time + if timeout > 0 { + after = time.After(timeout) + } else { + ch := make(chan time.Time) + defer close(ch) + after = ch + } + var lastEvent *Event + for _, condition := range conditions { + // check the next condition against the previous event and short circuit waiting for the next watch + if lastEvent != nil { + done, err := condition(*lastEvent) + if err != nil { + return lastEvent, err + } + if done { + continue + } + } + ConditionSucceeded: + for { + select { + case event, ok := <-ch: + if !ok { + return lastEvent, ErrWatchClosed + } + lastEvent = &event + + // TODO: check for watch expired error and retry watch from latest point? + done, err := condition(event) + if err != nil { + return lastEvent, err + } + if done { + break ConditionSucceeded + } + + case <-after: + return lastEvent, wait.ErrWaitTimeout + } + } + } + return lastEvent, nil +} diff --git a/tools/watch/until_test.go b/tools/watch/until_test.go new file mode 100644 index 00000000..e872c368 --- /dev/null +++ b/tools/watch/until_test.go @@ -0,0 +1,172 @@ +/* +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 watch + +import ( + "errors" + "strings" + "testing" + "time" + + "k8s.io/apimachinery/pkg/runtime" + "k8s.io/apimachinery/pkg/runtime/schema" + "k8s.io/apimachinery/pkg/util/wait" +) + +type fakePod struct { + name string +} + +func (obj *fakePod) GetObjectKind() schema.ObjectKind { return schema.EmptyObjectKind } +func (obj *fakePod) DeepCopyObject() runtime.Object { panic("DeepCopyObject not supported by fakePod") } + +func TestUntil(t *testing.T) { + fw := NewFake() + go func() { + var obj *fakePod + fw.Add(obj) + fw.Modify(obj) + }() + conditions := []ConditionFunc{ + func(event Event) (bool, error) { return event.Type == Added, nil }, + func(event Event) (bool, error) { return event.Type == Modified, nil }, + } + + timeout := time.Minute + lastEvent, err := Until(timeout, fw, conditions...) + if err != nil { + t.Fatalf("expected nil error, got %#v", err) + } + if lastEvent == nil { + t.Fatal("expected an event") + } + if lastEvent.Type != Modified { + t.Fatalf("expected MODIFIED event type, got %v", lastEvent.Type) + } + if got, isPod := lastEvent.Object.(*fakePod); !isPod { + t.Fatalf("expected a pod event, got %#v", got) + } +} + +func TestUntilMultipleConditions(t *testing.T) { + fw := NewFake() + go func() { + var obj *fakePod + fw.Add(obj) + }() + conditions := []ConditionFunc{ + func(event Event) (bool, error) { return event.Type == Added, nil }, + func(event Event) (bool, error) { return event.Type == Added, nil }, + } + + timeout := time.Minute + lastEvent, err := Until(timeout, fw, conditions...) + if err != nil { + t.Fatalf("expected nil error, got %#v", err) + } + if lastEvent == nil { + t.Fatal("expected an event") + } + if lastEvent.Type != Added { + t.Fatalf("expected MODIFIED event type, got %v", lastEvent.Type) + } + if got, isPod := lastEvent.Object.(*fakePod); !isPod { + t.Fatalf("expected a pod event, got %#v", got) + } +} + +func TestUntilMultipleConditionsFail(t *testing.T) { + fw := NewFake() + go func() { + var obj *fakePod + fw.Add(obj) + }() + conditions := []ConditionFunc{ + func(event Event) (bool, error) { return event.Type == Added, nil }, + func(event Event) (bool, error) { return event.Type == Added, nil }, + func(event Event) (bool, error) { return event.Type == Deleted, nil }, + } + + timeout := 10 * time.Second + lastEvent, err := Until(timeout, fw, conditions...) + if err != wait.ErrWaitTimeout { + t.Fatalf("expected ErrWaitTimeout error, got %#v", err) + } + if lastEvent == nil { + t.Fatal("expected an event") + } + if lastEvent.Type != Added { + t.Fatalf("expected ADDED event type, got %v", lastEvent.Type) + } + if got, isPod := lastEvent.Object.(*fakePod); !isPod { + t.Fatalf("expected a pod event, got %#v", got) + } +} + +func TestUntilTimeout(t *testing.T) { + fw := NewFake() + go func() { + var obj *fakePod + fw.Add(obj) + fw.Modify(obj) + }() + conditions := []ConditionFunc{ + func(event Event) (bool, error) { + return event.Type == Added, nil + }, + func(event Event) (bool, error) { + return event.Type == Modified, nil + }, + } + + timeout := time.Duration(0) + lastEvent, err := Until(timeout, fw, conditions...) + if err != nil { + t.Fatalf("expected nil error, got %#v", err) + } + if lastEvent == nil { + t.Fatal("expected an event") + } + if lastEvent.Type != Modified { + t.Fatalf("expected MODIFIED event type, got %v", lastEvent.Type) + } + if got, isPod := lastEvent.Object.(*fakePod); !isPod { + t.Fatalf("expected a pod event, got %#v", got) + } +} + +func TestUntilErrorCondition(t *testing.T) { + fw := NewFake() + go func() { + var obj *fakePod + fw.Add(obj) + }() + expected := "something bad" + conditions := []ConditionFunc{ + func(event Event) (bool, error) { return event.Type == Added, nil }, + func(event Event) (bool, error) { return false, errors.New(expected) }, + } + + timeout := time.Minute + _, err := Until(timeout, fw, conditions...) + if err == nil { + t.Fatal("expected an error") + } + if !strings.Contains(err.Error(), expected) { + t.Fatalf("expected %q in error string, got %q", expected, err.Error()) + } +}