87 lines
2.7 KiB
Go
87 lines
2.7 KiB
Go
/*
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Copyright 2016 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package watch
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import (
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"errors"
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"time"
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"k8s.io/apimachinery/pkg/util/wait"
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)
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// ConditionFunc returns true if the condition has been reached, false if it has not been reached yet,
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// or an error if the condition cannot be checked and should terminate. In general, it is better to define
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// level driven conditions over edge driven conditions (pod has ready=true, vs pod modified and ready changed
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// from false to true).
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type ConditionFunc func(event Event) (bool, error)
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// errWatchClosed is returned when the watch channel is closed before timeout in Until.
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var errWatchClosed = errors.New("watch closed before Until timeout")
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// Until reads items from the watch until each provided condition succeeds, and then returns the last watch
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// encountered. The first condition that returns an error terminates the watch (and the event is also returned).
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// If no event has been received, the returned event will be nil.
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// Conditions are satisfied sequentially so as to provide a useful primitive for higher level composition.
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// A zero timeout means to wait forever.
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func Until(timeout time.Duration, watcher Interface, conditions ...ConditionFunc) (*Event, error) {
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ch := watcher.ResultChan()
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defer watcher.Stop()
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var after <-chan time.Time
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if timeout > 0 {
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after = time.After(timeout)
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} else {
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ch := make(chan time.Time)
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defer close(ch)
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after = ch
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}
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var lastEvent *Event
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for _, condition := range conditions {
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// check the next condition against the previous event and short circuit waiting for the next watch
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if lastEvent != nil {
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done, err := condition(*lastEvent)
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if err != nil {
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return lastEvent, err
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}
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if done {
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continue
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}
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}
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ConditionSucceeded:
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for {
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select {
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case event, ok := <-ch:
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if !ok {
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return lastEvent, errWatchClosed
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}
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lastEvent = &event
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// TODO: check for watch expired error and retry watch from latest point?
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done, err := condition(event)
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if err != nil {
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return lastEvent, err
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}
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if done {
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break ConditionSucceeded
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}
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case <-after:
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return lastEvent, wait.ErrWaitTimeout
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}
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}
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}
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return lastEvent, nil
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}
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