sdk/go/dispatch/throttle.go

   1 package dispatch
   2
   3 import (
   4         "sync"
   5         "time"
   6 )
   7
   8 type throttleEnt struct {
   9         last time.Time // last attempt that was allowed
  10 }
  11
  12 type throttle struct {
  13         hold      time.Duration
  14         seen      map[string]*throttleEnt
  15         updated   sync.Cond
  16         setupOnce sync.Once
  17         mtx       sync.Mutex
  18 }
  19
  20 // Check checks whether there have been too many recent attempts with
  21 // the given uuid, and returns true if it's OK to attempt [again] now.
  22 func (t *throttle) Check(uuid string) bool {
  23         if t.hold == 0 {
  24                 return true
  25         }
  26         t.setupOnce.Do(t.setup)
  27         t.mtx.Lock()
  28         defer t.updated.Broadcast()
  29         defer t.mtx.Unlock()
  30         ent, ok := t.seen[uuid]
  31         if !ok {
  32                 t.seen[uuid] = &throttleEnt{last: time.Now()}
  33                 return true
  34         }
  35         if time.Since(ent.last) < t.hold {
  36                 return false
  37         }
  38         ent.last = time.Now()
  39         return true
  40 }
  41
  42 func (t *throttle) setup() {
  43         t.seen = make(map[string]*throttleEnt)
  44         t.updated.L = &t.mtx
  45         go func() {
  46                 for range time.NewTicker(t.hold).C {
  47                         t.mtx.Lock()
  48                         for uuid, ent := range t.seen {
  49                                 if time.Since(ent.last) >= t.hold {
  50                                         delete(t.seen, uuid)
  51                                 }
  52                         }
  53                         // don't bother cleaning again until the next update
  54                         t.updated.Wait()
  55                         t.mtx.Unlock()
  56                 }
  57         }()
  58 }