98 lines
2.2 KiB
Go
98 lines
2.2 KiB
Go
// Package stop implements a pattern for shutting down a group of processes.
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package stop
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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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//
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// The channel can either return one error or be closed.
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// Closing the channel signals a clean shutdown.
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// Stop() should return immediately and perform the actual shutdown in a
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// separate goroutine.
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Stop() <-chan error
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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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// Group is a collection of Stoppers that can be stopped all at once.
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type Group struct {
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stoppables []Func
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sync.Mutex
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}
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// NewGroup allocates a new Group.
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func NewGroup() *Group {
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return &Group{
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stoppables: make([]Func, 0),
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}
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}
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// Add appends a Stopper to the Group.
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func (cg *Group) 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 appends a Func to the Group.
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func (cg *Group) 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 Group.
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//
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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 *Group) 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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