98 lines
2.3 KiB
Go
98 lines
2.3 KiB
Go
// Package stopper implements a pattern for shutting down a group of processes.
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package stopper
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import (
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"sync"
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)
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// AlreadyStopped is a closed error channel to be used by Funcs when
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// an element was already stopped.
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var AlreadyStopped <-chan error
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// AlreadyStoppedFunc is a Func that returns AlreadyStopped.
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var AlreadyStoppedFunc = func() <-chan error { return AlreadyStopped }
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func init() {
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closeMe := make(chan error)
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close(closeMe)
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AlreadyStopped = closeMe
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}
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// Stopper is an interface that allows a clean shutdown.
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type Stopper interface {
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// Stop returns a channel that indicates whether the stop was
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// successful.
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// The channel can either return one error or be closed. Closing the
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// channel signals a clean shutdown.
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// The Stop function should return immediately and perform the actual
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// shutdown in a separate goroutine.
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Stop() <-chan error
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}
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// StopGroup is a group that can be stopped.
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type StopGroup struct {
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stoppables []Func
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sync.Mutex
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}
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// Func is a function that can be used to provide a clean shutdown.
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type Func func() <-chan error
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// NewStopGroup creates a new StopGroup.
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func NewStopGroup() *StopGroup {
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return &StopGroup{
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stoppables: make([]Func, 0),
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}
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}
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// Add adds a Stopper to the StopGroup.
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// On the next call to Stop(), the Stopper will be stopped.
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func (cg *StopGroup) Add(toAdd Stopper) {
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cg.Lock()
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defer cg.Unlock()
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cg.stoppables = append(cg.stoppables, toAdd.Stop)
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}
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// AddFunc adds a Func to the StopGroup.
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// On the next call to Stop(), the Func will be called.
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func (cg *StopGroup) AddFunc(toAddFunc Func) {
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cg.Lock()
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defer cg.Unlock()
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cg.stoppables = append(cg.stoppables, toAddFunc)
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}
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// Stop stops all members of the StopGroup.
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// Stopping will be done in a concurrent fashion.
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// The slice of errors returned contains all errors returned by stopping the
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// members.
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func (cg *StopGroup) Stop() []error {
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cg.Lock()
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defer cg.Unlock()
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var errors []error
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whenDone := make(chan struct{})
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waitChannels := make([]<-chan error, 0, len(cg.stoppables))
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for _, toStop := range cg.stoppables {
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waitFor := toStop()
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if waitFor == nil {
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panic("received a nil chan from Stop")
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}
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waitChannels = append(waitChannels, waitFor)
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}
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go func() {
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for _, waitForMe := range waitChannels {
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err := <-waitForMe
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if err != nil {
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errors = append(errors, err)
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}
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}
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close(whenDone)
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}()
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<-whenDone
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return errors
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}
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