Support http service graceful restart (#416)

* support http service graceful restart

* fix dependencies

vendor/github.com/facebookgo/clock/clock.go

@@ -0,0 +1,363 @@
+package clock
+
+import (
+	"runtime"
+	"sort"
+	"sync"
+	"time"
+)
+
+// Clock represents an interface to the functions in the standard library time
+// package. Two implementations are available in the clock package. The first
+// is a real-time clock which simply wraps the time package's functions. The
+// second is a mock clock which will only make forward progress when
+// programmatically adjusted.
+type Clock interface {
+	After(d time.Duration) <-chan time.Time
+	AfterFunc(d time.Duration, f func()) *Timer
+	Now() time.Time
+	Sleep(d time.Duration)
+	Tick(d time.Duration) <-chan time.Time
+	Ticker(d time.Duration) *Ticker
+	Timer(d time.Duration) *Timer
+}
+
+// New returns an instance of a real-time clock.
+func New() Clock {
+	return &clock{}
+}
+
+// clock implements a real-time clock by simply wrapping the time package functions.
+type clock struct{}
+
+func (c *clock) After(d time.Duration) <-chan time.Time { return time.After(d) }
+
+func (c *clock) AfterFunc(d time.Duration, f func()) *Timer {
+	return &Timer{timer: time.AfterFunc(d, f)}
+}
+
+func (c *clock) Now() time.Time { return time.Now() }
+
+func (c *clock) Sleep(d time.Duration) { time.Sleep(d) }
+
+func (c *clock) Tick(d time.Duration) <-chan time.Time { return time.Tick(d) }
+
+func (c *clock) Ticker(d time.Duration) *Ticker {
+	t := time.NewTicker(d)
+	return &Ticker{C: t.C, ticker: t}
+}
+
+func (c *clock) Timer(d time.Duration) *Timer {
+	t := time.NewTimer(d)
+	return &Timer{C: t.C, timer: t}
+}
+
+// Mock represents a mock clock that only moves forward programmically.
+// It can be preferable to a real-time clock when testing time-based functionality.
+type Mock struct {
+	mu     sync.Mutex
+	now    time.Time   // current time
+	timers clockTimers // tickers & timers
+
+	calls      Calls
+	waiting    []waiting
+	callsMutex sync.Mutex
+}
+
+// NewMock returns an instance of a mock clock.
+// The current time of the mock clock on initialization is the Unix epoch.
+func NewMock() *Mock {
+	return &Mock{now: time.Unix(0, 0)}
+}
+
+// Add moves the current time of the mock clock forward by the duration.
+// This should only be called from a single goroutine at a time.
+func (m *Mock) Add(d time.Duration) {
+	// Calculate the final current time.
+	t := m.now.Add(d)
+
+	// Continue to execute timers until there are no more before the new time.
+	for {
+		if !m.runNextTimer(t) {
+			break
+		}
+	}
+
+	// Ensure that we end with the new time.
+	m.mu.Lock()
+	m.now = t
+	m.mu.Unlock()
+
+	// Give a small buffer to make sure the other goroutines get handled.
+	gosched()
+}
+
+// runNextTimer executes the next timer in chronological order and moves the
+// current time to the timer's next tick time. The next time is not executed if
+// it's next time if after the max time. Returns true if a timer is executed.
+func (m *Mock) runNextTimer(max time.Time) bool {
+	m.mu.Lock()
+
+	// Sort timers by time.
+	sort.Sort(m.timers)
+
+	// If we have no more timers then exit.
+	if len(m.timers) == 0 {
+		m.mu.Unlock()
+		return false
+	}
+
+	// Retrieve next timer. Exit if next tick is after new time.
+	t := m.timers[0]
+	if t.Next().After(max) {
+		m.mu.Unlock()
+		return false
+	}
+
+	// Move "now" forward and unlock clock.
+	m.now = t.Next()
+	m.mu.Unlock()
+
+	// Execute timer.
+	t.Tick(m.now)
+	return true
+}
+
+// After waits for the duration to elapse and then sends the current time on the returned channel.
+func (m *Mock) After(d time.Duration) <-chan time.Time {
+	defer m.inc(&m.calls.After)
+	return m.Timer(d).C
+}
+
+// AfterFunc waits for the duration to elapse and then executes a function.
+// A Timer is returned that can be stopped.
+func (m *Mock) AfterFunc(d time.Duration, f func()) *Timer {
+	defer m.inc(&m.calls.AfterFunc)
+	t := m.Timer(d)
+	t.C = nil
+	t.fn = f
+	return t
+}
+
+// Now returns the current wall time on the mock clock.
+func (m *Mock) Now() time.Time {
+	defer m.inc(&m.calls.Now)
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	return m.now
+}
+
+// Sleep pauses the goroutine for the given duration on the mock clock.
+// The clock must be moved forward in a separate goroutine.
+func (m *Mock) Sleep(d time.Duration) {
+	defer m.inc(&m.calls.Sleep)
+	<-m.After(d)
+}
+
+// Tick is a convenience function for Ticker().
+// It will return a ticker channel that cannot be stopped.
+func (m *Mock) Tick(d time.Duration) <-chan time.Time {
+	defer m.inc(&m.calls.Tick)
+	return m.Ticker(d).C
+}
+
+// Ticker creates a new instance of Ticker.
+func (m *Mock) Ticker(d time.Duration) *Ticker {
+	defer m.inc(&m.calls.Ticker)
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	ch := make(chan time.Time)
+	t := &Ticker{
+		C:    ch,
+		c:    ch,
+		mock: m,
+		d:    d,
+		next: m.now.Add(d),
+	}
+	m.timers = append(m.timers, (*internalTicker)(t))
+	return t
+}
+
+// Timer creates a new instance of Timer.
+func (m *Mock) Timer(d time.Duration) *Timer {
+	defer m.inc(&m.calls.Timer)
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	ch := make(chan time.Time)
+	t := &Timer{
+		C:    ch,
+		c:    ch,
+		mock: m,
+		next: m.now.Add(d),
+	}
+	m.timers = append(m.timers, (*internalTimer)(t))
+	return t
+}
+
+func (m *Mock) removeClockTimer(t clockTimer) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	for i, timer := range m.timers {
+		if timer == t {
+			copy(m.timers[i:], m.timers[i+1:])
+			m.timers[len(m.timers)-1] = nil
+			m.timers = m.timers[:len(m.timers)-1]
+			break
+		}
+	}
+	sort.Sort(m.timers)
+}
+
+func (m *Mock) inc(addr *uint32) {
+	m.callsMutex.Lock()
+	defer m.callsMutex.Unlock()
+	*addr++
+	var newWaiting []waiting
+	for _, w := range m.waiting {
+		if m.calls.atLeast(w.expected) {
+			close(w.done)
+			continue
+		}
+		newWaiting = append(newWaiting, w)
+	}
+	m.waiting = newWaiting
+}
+
+// Wait waits for at least the relevant calls before returning. The expected
+// Calls are always over the lifetime of the Mock. Values in the Calls struct
+// are used as the minimum number of calls, this allows you to wait for only
+// the calls you care about.
+func (m *Mock) Wait(s Calls) {
+	m.callsMutex.Lock()
+	if m.calls.atLeast(s) {
+		m.callsMutex.Unlock()
+		return
+	}
+	done := make(chan struct{})
+	m.waiting = append(m.waiting, waiting{expected: s, done: done})
+	m.callsMutex.Unlock()
+	<-done
+}
+
+// clockTimer represents an object with an associated start time.
+type clockTimer interface {
+	Next() time.Time
+	Tick(time.Time)
+}
+
+// clockTimers represents a list of sortable timers.
+type clockTimers []clockTimer
+
+func (a clockTimers) Len() int           { return len(a) }
+func (a clockTimers) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
+func (a clockTimers) Less(i, j int) bool { return a[i].Next().Before(a[j].Next()) }
+
+// Timer represents a single event.
+// The current time will be sent on C, unless the timer was created by AfterFunc.
+type Timer struct {
+	C     <-chan time.Time
+	c     chan time.Time
+	timer *time.Timer // realtime impl, if set
+	next  time.Time   // next tick time
+	mock  *Mock       // mock clock, if set
+	fn    func()      // AfterFunc function, if set
+}
+
+// Stop turns off the ticker.
+func (t *Timer) Stop() {
+	if t.timer != nil {
+		t.timer.Stop()
+	} else {
+		t.mock.removeClockTimer((*internalTimer)(t))
+	}
+}
+
+type internalTimer Timer
+
+func (t *internalTimer) Next() time.Time { return t.next }
+func (t *internalTimer) Tick(now time.Time) {
+	if t.fn != nil {
+		t.fn()
+	} else {
+		t.c <- now
+	}
+	t.mock.removeClockTimer((*internalTimer)(t))
+	gosched()
+}
+
+// Ticker holds a channel that receives "ticks" at regular intervals.
+type Ticker struct {
+	C      <-chan time.Time
+	c      chan time.Time
+	ticker *time.Ticker  // realtime impl, if set
+	next   time.Time     // next tick time
+	mock   *Mock         // mock clock, if set
+	d      time.Duration // time between ticks
+}
+
+// Stop turns off the ticker.
+func (t *Ticker) Stop() {
+	if t.ticker != nil {
+		t.ticker.Stop()
+	} else {
+		t.mock.removeClockTimer((*internalTicker)(t))
+	}
+}
+
+type internalTicker Ticker
+
+func (t *internalTicker) Next() time.Time { return t.next }
+func (t *internalTicker) Tick(now time.Time) {
+	select {
+	case t.c <- now:
+	case <-time.After(1 * time.Millisecond):
+	}
+	t.next = now.Add(t.d)
+	gosched()
+}
+
+// Sleep momentarily so that other goroutines can process.
+func gosched() { runtime.Gosched() }
+
+// Calls keeps track of the count of calls for each of the methods on the Clock
+// interface.
+type Calls struct {
+	After     uint32
+	AfterFunc uint32
+	Now       uint32
+	Sleep     uint32
+	Tick      uint32
+	Ticker    uint32
+	Timer     uint32
+}
+
+// atLeast returns true if at least the number of calls in o have been made.
+func (c Calls) atLeast(o Calls) bool {
+	if c.After < o.After {
+		return false
+	}
+	if c.AfterFunc < o.AfterFunc {
+		return false
+	}
+	if c.Now < o.Now {
+		return false
+	}
+	if c.Sleep < o.Sleep {
+		return false
+	}
+	if c.Tick < o.Tick {
+		return false
+	}
+	if c.Ticker < o.Ticker {
+		return false
+	}
+	if c.Timer < o.Timer {
+		return false
+	}
+	return true
+}
+
+type waiting struct {
+	expected Calls
+	done     chan struct{}
+}