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87 lines
2.7 KiB
87 lines
2.7 KiB
/* |
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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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