105 lines
2.0 KiB
Go
105 lines
2.0 KiB
Go
package multistep
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import (
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"context"
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"sync"
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"sync/atomic"
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)
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type runState int32
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const (
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stateIdle runState = iota
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stateRunning
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stateCancelling
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)
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// BasicRunner is a Runner that just runs the given slice of steps.
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type BasicRunner struct {
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// Steps is a slice of steps to run. Once set, this should _not_ be
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// modified.
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Steps []Step
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cancel context.CancelFunc
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doneCh chan struct{}
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state runState
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l sync.Mutex
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}
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func (b *BasicRunner) Run(state StateBag) {
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ctx, cancel := context.WithCancel(context.Background())
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b.l.Lock()
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if b.state != stateIdle {
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panic("already running")
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}
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doneCh := make(chan struct{})
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b.cancel = cancel
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b.doneCh = doneCh
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b.state = stateRunning
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b.l.Unlock()
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defer func() {
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b.l.Lock()
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b.cancel = nil
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b.doneCh = nil
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b.state = stateIdle
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close(doneCh)
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b.l.Unlock()
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}()
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// This goroutine listens for cancels and puts the StateCancelled key
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// as quickly as possible into the state bag to mark it.
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go func() {
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select {
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case <-ctx.Done():
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// Flag cancel and wait for finish
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state.Put(StateCancelled, true)
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<-doneCh
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case <-doneCh:
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}
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}()
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for _, step := range b.Steps {
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// We also check for cancellation here since we can't be sure
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// the goroutine that is running to set it actually ran.
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if runState(atomic.LoadInt32((*int32)(&b.state))) == stateCancelling {
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state.Put(StateCancelled, true)
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break
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}
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action := step.Run(ctx, state)
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defer step.Cleanup(state)
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if _, ok := state.GetOk(StateCancelled); ok {
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break
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}
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if action == ActionHalt {
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state.Put(StateHalted, true)
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break
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}
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}
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}
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func (b *BasicRunner) Cancel() {
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b.l.Lock()
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switch b.state {
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case stateIdle:
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// Not running, so Cancel is... done.
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b.l.Unlock()
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return
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case stateRunning:
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// Running, so mark that we cancelled and set the state
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b.cancel()
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b.state = stateCancelling
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fallthrough
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case stateCancelling:
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// Already cancelling, so just wait until we're done
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ch := b.doneCh
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b.l.Unlock()
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<-ch
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}
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}
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