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wait.go
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/
wait.go
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// Copyright 2016 The rkt 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 pod
import (
"time"
"github.com/rkt/rkt/pkg/lock"
"golang.org/x/net/context"
)
// WaitFinished waits for a pod to finish by polling every 100 milliseconds
// or until the given context is cancelled. This method refreshes the pod state.
// It is the caller's responsibility to determine the actual terminal state.
func (p *Pod) WaitFinished(ctx context.Context) error {
f := func() bool {
switch err := p.TrySharedLock(); err {
case nil:
// the pod is now locked successfully, hence one of the running phases passed.
// continue with unlocking the pod immediately below.
case lock.ErrLocked:
// pod is still locked, hence we are still in a running phase.
// i.e. in pepare, run, exitedGarbage, garbage state.
return false
default:
// some error occurred, bail out.
return true
}
// unlock immediately
if err := p.Unlock(); err != nil {
return true
}
if err := p.refreshState(); err != nil {
return true
}
// if we're in the gap between preparing and running in a split prepare/run-prepared usage, take a nap
if p.isPrepared {
time.Sleep(time.Second)
}
return p.IsFinished()
}
return retry(ctx, f, 100*time.Millisecond)
}
// WaitReady blocks until the pod is ready by polling the readiness state every 100 milliseconds
// or until the given context is cancelled. This method refreshes the pod state.
func (p *Pod) WaitReady(ctx context.Context) error {
f := func() bool {
if err := p.refreshState(); err != nil {
return false
}
return p.IsSupervisorReady()
}
return retry(ctx, f, 100*time.Millisecond)
}
// retry calls function f indefinitely with the given delay between invocations
// until f returns true or the given context is cancelled.
// It returns immediately without delay in case function f immediately returns true.
func retry(ctx context.Context, f func() bool, delay time.Duration) error {
if f() {
return nil
}
ticker := time.NewTicker(delay)
errChan := make(chan error)
go func() {
defer close(errChan)
for {
select {
case <-ctx.Done():
errChan <- ctx.Err()
return
case <-ticker.C:
if f() {
return
}
}
}
}()
return <-errChan
}