mirror of https://github.com/k3s-io/k3s
237 lines
9.2 KiB
Go
237 lines
9.2 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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"context"
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"errors"
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"fmt"
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"time"
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"k8s.io/apimachinery/pkg/api/meta"
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metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
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"k8s.io/apimachinery/pkg/runtime"
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"k8s.io/apimachinery/pkg/util/wait"
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"k8s.io/apimachinery/pkg/watch"
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"k8s.io/client-go/tools/cache"
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"k8s.io/klog"
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)
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// PreconditionFunc 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 failed or detected an error state.
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type PreconditionFunc func(store cache.Store) (bool, error)
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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 watch.Event) (bool, error)
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// ErrWatchClosed is returned when the watch channel is closed before timeout in UntilWithoutRetry.
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var ErrWatchClosed = errors.New("watch closed before UntilWithoutRetry timeout")
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// UntilWithoutRetry 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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// Waits until context deadline or until context is canceled.
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//
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// Warning: Unless you have a very specific use case (probably a special Watcher) don't use this function!!!
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// Warning: This will fail e.g. on API timeouts and/or 'too old resource version' error.
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// Warning: You are most probably looking for a function *Until* or *UntilWithSync* below,
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// Warning: solving such issues.
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// TODO: Consider making this function private to prevent misuse when the other occurrences in our codebase are gone.
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func UntilWithoutRetry(ctx context.Context, watcher watch.Interface, conditions ...ConditionFunc) (*watch.Event, error) {
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ch := watcher.ResultChan()
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defer watcher.Stop()
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var lastEvent *watch.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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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 <-ctx.Done():
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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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// Until wraps the watcherClient's watch function with RetryWatcher making sure that watcher gets restarted in case of errors.
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// The initialResourceVersion will be given to watch method when first called. It shall not be "" or "0"
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// given the underlying WATCH call issues (#74022). If you want the initial list ("", "0") done for you use ListWatchUntil instead.
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// Remaining behaviour is identical to function UntilWithoutRetry. (See above.)
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// Until can deal with API timeouts and lost connections.
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// It guarantees you to see all events and in the order they happened.
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// Due to this guarantee there is no way it can deal with 'Resource version too old error'. It will fail in this case.
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// (See `UntilWithSync` if you'd prefer to recover from all the errors including RV too old by re-listing
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// those items. In normal code you should care about being level driven so you'd not care about not seeing all the edges.)
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// The most frequent usage for Until would be a test where you want to verify exact order of events ("edges").
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func Until(ctx context.Context, initialResourceVersion string, watcherClient cache.Watcher, conditions ...ConditionFunc) (*watch.Event, error) {
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w, err := NewRetryWatcher(initialResourceVersion, watcherClient)
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if err != nil {
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return nil, err
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}
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return UntilWithoutRetry(ctx, w, conditions...)
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}
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// UntilWithSync creates an informer from lw, optionally checks precondition when the store is synced,
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// and watches the output until each provided condition succeeds, in a way that is identical
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// to function UntilWithoutRetry. (See above.)
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// UntilWithSync can deal with all errors like API timeout, lost connections and 'Resource version too old'.
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// It is the only function that can recover from 'Resource version too old', Until and UntilWithoutRetry will
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// just fail in that case. On the other hand it can't provide you with guarantees as strong as using simple
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// Watch method with Until. It can skip some intermediate events in case of watch function failing but it will
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// re-list to recover and you always get an event, if there has been a change, after recovery.
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// Also with the current implementation based on DeltaFIFO, order of the events you receive is guaranteed only for
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// particular object, not between more of them even it's the same resource.
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// The most frequent usage would be a command that needs to watch the "state of the world" and should't fail, like:
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// waiting for object reaching a state, "small" controllers, ...
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func UntilWithSync(ctx context.Context, lw cache.ListerWatcher, objType runtime.Object, precondition PreconditionFunc, conditions ...ConditionFunc) (*watch.Event, error) {
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indexer, informer, watcher, done := NewIndexerInformerWatcher(lw, objType)
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// We need to wait for the internal informers to fully stop so it's easier to reason about
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// and it works with non-thread safe clients.
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defer func() { <-done }()
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// Proxy watcher can be stopped multiple times so it's fine to use defer here to cover alternative branches and
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// let UntilWithoutRetry to stop it
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defer watcher.Stop()
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if precondition != nil {
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if !cache.WaitForCacheSync(ctx.Done(), informer.HasSynced) {
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return nil, fmt.Errorf("UntilWithSync: unable to sync caches: %v", ctx.Err())
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}
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done, err := precondition(indexer)
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if err != nil {
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return nil, err
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}
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if done {
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return nil, nil
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}
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}
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return UntilWithoutRetry(ctx, watcher, conditions...)
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}
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// ContextWithOptionalTimeout wraps context.WithTimeout and handles infinite timeouts expressed as 0 duration.
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func ContextWithOptionalTimeout(parent context.Context, timeout time.Duration) (context.Context, context.CancelFunc) {
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if timeout < 0 {
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// This should be handled in validation
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klog.Errorf("Timeout for context shall not be negative!")
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timeout = 0
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}
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if timeout == 0 {
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return context.WithCancel(parent)
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}
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return context.WithTimeout(parent, timeout)
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}
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// ListWatchUntil first lists objects, converts them into synthetic ADDED events
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// and checks conditions for those synthetic events. If the conditions have not been reached so far
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// it continues by calling Until which establishes a watch from resourceVersion of the list call
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// to evaluate those conditions based on new events.
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// ListWatchUntil provides the same guarantees as Until and replaces the old WATCH from RV "" (or "0")
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// which was mixing list and watch calls internally and having severe design issues. (see #74022)
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// There is no resourceVersion order guarantee for the initial list and those synthetic events.
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func ListWatchUntil(ctx context.Context, lw cache.ListerWatcher, conditions ...ConditionFunc) (*watch.Event, error) {
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if len(conditions) == 0 {
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return nil, nil
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}
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list, err := lw.List(metav1.ListOptions{})
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if err != nil {
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return nil, err
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}
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initialItems, err := meta.ExtractList(list)
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if err != nil {
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return nil, err
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}
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// use the initial items as simulated "adds"
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var lastEvent *watch.Event
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currIndex := 0
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passedConditions := 0
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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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passedConditions = passedConditions + 1
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continue
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}
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}
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ConditionSucceeded:
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for currIndex < len(initialItems) {
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lastEvent = &watch.Event{Type: watch.Added, Object: initialItems[currIndex]}
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currIndex++
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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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passedConditions = passedConditions + 1
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break ConditionSucceeded
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}
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}
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}
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if passedConditions == len(conditions) {
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return lastEvent, nil
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}
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remainingConditions := conditions[passedConditions:]
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metaObj, err := meta.ListAccessor(list)
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if err != nil {
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return nil, err
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}
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currResourceVersion := metaObj.GetResourceVersion()
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return Until(ctx, currResourceVersion, lw, remainingConditions...)
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}
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