Refactor timer gate and fix goroutine leak problem

common/clock/event_timer_gate.go

@@ -0,0 +1,147 @@
+// The MIT License (MIT)
+
+// Copyright (c) 2017-2020 Uber Technologies Inc.
+
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+package clock
+
+import (
+	"sync"
+	"time"
+)
+
+type (
+	// EventTimerGate is a TimerGate in which the time is retrieved from external events via SetCurrentTime method.
+	EventTimerGate interface {
+		TimerGate
+		// SetCurrentTime set the current time, and additionally fire the fire chan
+		// if new "current" time is after the fire time, return true if
+		// "current" is actually updated
+		SetCurrentTime(t time.Time) bool
+	}
+
+	eventTimerGateImpl struct {
+		// the channel which will be used to proxy the fired timer
+		fireChan chan time.Time
+
+		// lock for timer and fire time
+		sync.RWMutex
+		// view of current time
+		currentTime time.Time
+		// time which timer will fire
+		fireTime time.Time
+	}
+)
+
+// NewEventTimerGate create a new event timer gate instance
+func NewEventTimerGate(currentTime time.Time) EventTimerGate {
+	timer := &eventTimerGateImpl{
+		currentTime:    currentTime,
+		fireTime: time.Time{},
+		fireChan:       make(chan time.Time, 1),
+	}
+	return timer
+}
+
+func (t *eventTimerGateImpl) Chan() <-chan time.Time {
+	return t.fireChan
+}
+
+func (t *eventTimerGateImpl) FireAfter(now time.Time) bool {
+	t.RLock()
+	defer t.RUnlock()
+
+	active := t.currentTime.Before(t.fireTime)
+	return active && t.fireTime.After(now)
+}
+
+func (t *eventTimerGateImpl) Update(nextTime time.Time) bool {
+	t.Lock()
+	defer t.Unlock()
+
+	active := t.currentTime.Before(t.fireTime)
+	if active {
+		if t.fireTime.Before(nextTime) {
+			// current time < next wake up time < next time
+			return false
+		}
+
+		if t.currentTime.Before(nextTime) {
+			// current time < next time <= next wake up time
+			t.fireTime = nextTime
+			return true
+		}
+
+		// next time <= current time < next wake up time
+		t.fireTime = nextTime
+		t.fire(t.currentTime)
+		return true
+	}
+
+	// this means the timer, before stopped, has already fired / never active
+	if !t.currentTime.Before(nextTime) {
+		// next time is <= current time, need to fire immediately
+		// whether to update next wake up time or not is irrelevent
+		t.fire(t.currentTime)
+	} else {
+		// next time > current time
+		t.fireTime = nextTime
+	}
+	return true
+}
+
+func (t *eventTimerGateImpl) Stop() {
+	t.Lock()
+	defer t.Unlock()
+	t.fireTime = time.Time{}
+}
+
+func (t *eventTimerGateImpl) SetCurrentTime(currentTime time.Time) bool {
+	t.Lock()
+	defer t.Unlock()
+
+	if !t.currentTime.Before(currentTime) {
+		// new current time is <= current time
+		return false
+	}
+
+	// NOTE: do not update the current time now
+	if !t.currentTime.Before(t.fireTime) {
+		// current time already >= next wakeup time
+		// avoid duplicate fire
+		t.currentTime = currentTime
+		return true
+	}
+
+	t.currentTime = currentTime
+	if !t.currentTime.Before(t.fireTime) {
+		t.fire(t.currentTime)
+	}
+	return true
+}
+
+func (t *eventTimerGateImpl) fire(fireTime time.Time) {
+	select {
+	case t.fireChan <- fireTime:
+		// timer successfully triggered
+	default:
+		// timer already triggered, pass
+	}
+}