mirror of
https://github.com/crazy-max/diun.git
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96 lines
2.8 KiB
Go
96 lines
2.8 KiB
Go
/*
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Copyright 2023 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 wait
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import (
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"context"
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"time"
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"k8s.io/apimachinery/pkg/util/runtime"
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)
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// loopConditionUntilContext executes the provided condition at intervals defined by
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// the provided timer until the provided context is cancelled, the condition returns
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// true, or the condition returns an error. If sliding is true, the period is computed
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// after condition runs. If it is false then period includes the runtime for condition.
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// If immediate is false the first delay happens before any call to condition, if
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// immediate is true the condition will be invoked before waiting and guarantees that
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// the condition is invoked at least once, regardless of whether the context has been
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// cancelled. The returned error is the error returned by the last condition or the
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// context error if the context was terminated.
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//
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// This is the common loop construct for all polling in the wait package.
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func loopConditionUntilContext(ctx context.Context, t Timer, immediate, sliding bool, condition ConditionWithContextFunc) error {
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defer t.Stop()
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var timeCh <-chan time.Time
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doneCh := ctx.Done()
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if !sliding {
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timeCh = t.C()
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}
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// if immediate is true the condition is
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// guaranteed to be executed at least once,
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// if we haven't requested immediate execution, delay once
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if immediate {
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if ok, err := func() (bool, error) {
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defer runtime.HandleCrash()
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return condition(ctx)
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}(); err != nil || ok {
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return err
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}
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}
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if sliding {
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timeCh = t.C()
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}
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for {
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// Wait for either the context to be cancelled or the next invocation be called
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select {
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case <-doneCh:
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return ctx.Err()
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case <-timeCh:
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}
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// IMPORTANT: Because there is no channel priority selection in golang
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// it is possible for very short timers to "win" the race in the previous select
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// repeatedly even when the context has been canceled. We therefore must
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// explicitly check for context cancellation on every loop and exit if true to
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// guarantee that we don't invoke condition more than once after context has
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// been cancelled.
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if err := ctx.Err(); err != nil {
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return err
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}
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if !sliding {
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t.Next()
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}
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if ok, err := func() (bool, error) {
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defer runtime.HandleCrash()
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return condition(ctx)
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}(); err != nil || ok {
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return err
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}
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if sliding {
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t.Next()
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}
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}
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}
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