84 lines
1.8 KiB
Go
84 lines
1.8 KiB
Go
// Package up is used to run a function for some duration. If a new function is added while a previous run is
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// still ongoing, nothing new will be executed.
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package up
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import (
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"sync"
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"time"
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)
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// Probe is used to run a single Func until it returns true (indicating a target is healthy). If an Func
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// is already in progress no new one will be added, i.e. there is always a maximum of 1 checks in flight.
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type Probe struct {
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do chan Func
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stop chan bool
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target string
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sync.Mutex
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inprogress int
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}
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// Func is used to determine if a target is alive. If so this function must return nil.
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type Func func() error
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// New returns a pointer to an intialized Probe.
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func New() *Probe {
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return &Probe{stop: make(chan bool), do: make(chan Func)}
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}
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// Do will probe target, if a probe is already in progress this is a noop.
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func (p *Probe) Do(f Func) { p.do <- f }
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// Stop stops the probing.
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func (p *Probe) Stop() { p.stop <- true }
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// Start will start the probe manager, after which probes can be initialized with Do.
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func (p *Probe) Start(interval time.Duration) { go p.start(interval) }
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func (p *Probe) start(interval time.Duration) {
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for {
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select {
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case <-p.stop:
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p.Lock()
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p.inprogress = stop
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p.Unlock()
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return
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case f := <-p.do:
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p.Lock()
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if p.inprogress == active || p.inprogress == stop {
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p.Unlock()
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continue
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}
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p.inprogress = active
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p.Unlock()
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// Passed the lock. Now run f for as long it returns false. If a true is returned
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// we return from the goroutine and we can accept another Func to run.
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go func() {
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for {
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if err := f(); err == nil {
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break
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}
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time.Sleep(interval)
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p.Lock()
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if p.inprogress == stop {
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p.Unlock()
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return
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}
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p.Unlock()
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}
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p.Lock()
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p.inprogress = idle
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p.Unlock()
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}()
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}
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}
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}
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const (
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idle = iota
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active
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stop
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)
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