File: retry_test.go

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golang-gopkg-retry.v1 0.0~git20161025.0.c09f6b8-1
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// Copyright 2011, 2012, 2013 Canonical Ltd.
// Licensed under the LGPLv3, see LICENCE file for details.

package retry_test // import "gopkg.in/retry.v1"

import (
	"sort"
	"sync"
	"time"

	gc "gopkg.in/check.v1"

	"gopkg.in/retry.v1"
)

type retrySuite struct{}

var _ = gc.Suite(&retrySuite{})

func (*retrySuite) TestAttemptTiming(c *gc.C) {
	testAttempt := retry.Regular{
		Total: 0.25e9,
		Delay: 0.1e9,
	}
	want := []time.Duration{0, 0.1e9, 0.2e9, 0.2e9}
	got := make([]time.Duration, 0, len(want)) // avoid allocation when testing timing
	t0 := time.Now()
	a := testAttempt.Start(nil)
	for a.Next() {
		got = append(got, time.Now().Sub(t0))
	}
	got = append(got, time.Now().Sub(t0))
	c.Assert(a.Stopped(), gc.Equals, false)
	c.Assert(got, gc.HasLen, len(want))
	const margin = 0.01e9
	for i, got := range want {
		lo := want[i] - margin
		hi := want[i] + margin
		if got < lo || got > hi {
			c.Errorf("attempt %d want %g got %g", i, want[i].Seconds(), got.Seconds())
		}
	}
}

func (*retrySuite) TestAttemptNextMore(c *gc.C) {
	a := retry.Regular{}.Start(nil)
	c.Assert(a.Next(), gc.Equals, true)
	c.Assert(a.Next(), gc.Equals, false)

	a = retry.Regular{}.Start(nil)
	c.Assert(a.Next(), gc.Equals, true)
	c.Assert(a.More(), gc.Equals, false)
	c.Assert(a.Next(), gc.Equals, false)

	a = retry.Regular{Total: 2e8}.Start(nil)
	c.Assert(a.Next(), gc.Equals, true)
	c.Assert(a.More(), gc.Equals, true)
	time.Sleep(2e8)
	c.Assert(a.More(), gc.Equals, true)
	c.Assert(a.Next(), gc.Equals, true)
	c.Assert(a.Next(), gc.Equals, false)

	a = retry.Regular{Total: 1e8, Min: 2}.Start(nil)
	time.Sleep(1e8)
	c.Assert(a.Next(), gc.Equals, true)
	c.Assert(a.More(), gc.Equals, true)
	c.Assert(a.Next(), gc.Equals, true)
	c.Assert(a.More(), gc.Equals, false)
	c.Assert(a.Next(), gc.Equals, false)
}

func (*retrySuite) TestAttemptWithStop(c *gc.C) {
	stop := make(chan struct{})
	close(stop)
	done := make(chan struct{})
	go func() {
		strategy := retry.Regular{
			Delay: 5 * time.Second,
			Total: 30 * time.Second,
		}
		a := retry.StartWithCancel(strategy, nil, stop)
		for a.Next() {
			c.Errorf("unexpected attempt")
		}
		c.Check(a.Stopped(), gc.Equals, true)
		close(done)
	}()
	assertReceive(c, done, "attempt loop abort")
}

func (*retrySuite) TestAttemptWithLaterStop(c *gc.C) {
	clock := NewClock(time.Now())
	stop := make(chan struct{})
	done := make(chan struct{})
	progress := make(chan struct{}, 10)
	go func() {
		strategy := retry.Regular{
			Delay: 5 * time.Second,
			Total: 30 * time.Second,
		}
		a := retry.StartWithCancel(strategy, clock, stop)
		for a.Next() {
			progress <- struct{}{}
		}
		c.Check(a.Stopped(), gc.Equals, true)
		close(done)
	}()
	assertReceive(c, progress, "progress")
	clock.Advance(5 * time.Second)
	assertReceive(c, progress, "progress")
	clock.Advance(2 * time.Second)
	close(stop)
	assertReceive(c, done, "attempt loop abort")
	select {
	case <-progress:
		c.Fatalf("unxpected loop iteration after stop")
	default:
	}
}

func (*retrySuite) TestAttemptWithMockClock(c *gc.C) {
	clock := NewClock(time.Now())
	strategy := retry.Regular{
		Delay: 5 * time.Second,
		Total: 30 * time.Second,
	}
	progress := make(chan struct{})
	done := make(chan struct{})
	go func() {
		for a := strategy.Start(clock); a.Next(); {
			progress <- struct{}{}
		}
		close(done)
	}()
	assertReceive(c, progress, "progress first time")
	clock.Advance(5 * time.Second)
	assertReceive(c, progress, "progress second time")
	clock.Advance(5 * time.Second)
	assertReceive(c, progress, "progress third time")
	clock.Advance(30 * time.Second)
	assertReceive(c, progress, "progress fourth time")
	assertReceive(c, done, "loop finish")
}

type strategyTest struct {
	about      string
	strategy   retry.Strategy
	calls      []nextCall
	terminates bool
}

type nextCall struct {
	// t holds the time since the timer was started that
	// the Next call will be made.
	t time.Duration
	// delay holds the length of time that a call made at
	// time t is expected to sleep for.
	sleep time.Duration
}

var strategyTests = []strategyTest{{
	about: "regular retry (same params as TestAttemptTiming)",
	strategy: retry.Regular{
		Total: 0.25e9,
		Delay: 0.1e9,
	},
	calls: []nextCall{
		{0, 0},
		{0, 0.1e9},
		{0.1e9, 0.1e9},
		{0.2e9, 0},
	},
	terminates: true,
}, {
	about: "regular retry with calls at different times",
	strategy: retry.Regular{
		Total: 2.5e9,
		Delay: 1e9,
	},
	calls: []nextCall{
		{0.5e9, 0},
		{0.5e9, 0.5e9},
		{1.1e9, 0.9e9},
		{2.2e9, 0},
	},
	terminates: true,
}, {
	about: "regular retry with call after next deadline",
	strategy: retry.Regular{
		Total: 3.5e9,
		Delay: 1e9,
	},
	calls: []nextCall{
		{0.5e9, 0},
		// We call Next at well beyond the deadline,
		// so we get a zero delay, but subsequent events
		// resume pace.
		{2e9, 0},
		{2.1e9, 0.9e9},
		{3e9, 0},
	},
	terminates: true,
}, {
	about: "exponential retry",
	strategy: retry.Exponential{
		Initial: 1e9,
		Factor:  2,
	},
	calls: []nextCall{
		{0, 0},
		{0.1e9, 0.9e9},
		{1e9, 2e9},
		{3e9, 4e9},
		{7e9, 8e9},
	},
}, {
	about: "time-limited exponential retry",
	strategy: retry.LimitTime(5e9, retry.Exponential{
		Initial: 1e9,
		Factor:  2,
	}),
	calls: []nextCall{
		{0, 0},
		{0.1e9, 0.9e9},
		{1e9, 2e9},
		{3e9, 0},
	},
	terminates: true,
}, {
	about: "count-limited exponential retry",
	strategy: retry.LimitCount(2, retry.Exponential{
		Initial: 1e9,
		Factor:  2,
	}),
	calls: []nextCall{
		{0, 0},
		{0.1e9, 0.9e9},
		{1e9, 0},
	},
	terminates: true,
}}

func (*retrySuite) TestStrategies(c *gc.C) {
	for i, test := range strategyTests {
		c.Logf("test %d: %s", i, test.about)
		testStrategy(c, test)
	}
}

func testStrategy(c *gc.C, test strategyTest) {
	t0 := time.Now()
	clk := &mockClock{
		now: t0,
	}
	a := retry.Start(test.strategy, clk)
	for i, call := range test.calls {
		c.Logf("call %d - %v", i, call.t)
		clk.now = t0.Add(call.t)
		ok := a.Next()
		expectTerminate := test.terminates && i == len(test.calls)-1
		c.Assert(ok, gc.Equals, !expectTerminate)
		if got, want := clk.now.Sub(t0), call.t+call.sleep; !closeTo(got, want) {
			c.Fatalf("incorrect time after Next; got %v want %v", got, want)
		}
		if ok {
			c.Assert(a.Count(), gc.Equals, i+1)
		}
	}
}

func (*retrySuite) TestGapBetweenMoreAndNext(c *gc.C) {
	t0 := time.Now().UTC()
	clk := &mockClock{
		now: t0,
	}
	a := (&retry.Regular{
		Min:   3,
		Delay: time.Second,
	}).Start(clk)
	c.Assert(a.Next(), gc.Equals, true)
	c.Assert(clk.now, gc.Equals, t0)

	clk.now = clk.now.Add(500 * time.Millisecond)
	// Sanity check that the first iteration sleeps for half a second.
	c.Assert(a.More(), gc.Equals, true)
	c.Assert(a.Next(), gc.Equals, true)
	c.Assert(clk.now.Sub(t0), gc.Equals, t0.Add(time.Second).Sub(t0))

	clk.now = clk.now.Add(500 * time.Millisecond)
	c.Assert(a.More(), gc.Equals, true)

	// Add a delay between calling More and Next.
	// Next should wait until the correct time anyway.
	clk.now = clk.now.Add(250 * time.Millisecond)
	c.Assert(a.More(), gc.Equals, true)
	c.Assert(a.Next(), gc.Equals, true)
	c.Assert(clk.now.Sub(t0), gc.Equals, t0.Add(2*time.Second).Sub(t0))
}

// closeTo reports whether d0 and d1 are close enough
// to one another to cater for inaccuracies of floating point arithmetic.
func closeTo(d0, d1 time.Duration) bool {
	const margin = 20 * time.Nanosecond
	diff := d1 - d0
	if diff < 0 {
		diff = -diff
	}
	return diff < margin
}

type mockClock struct {
	now   time.Time
	sleep func(d time.Duration)
}

func (c *mockClock) After(d time.Duration) <-chan time.Time {
	c.now = c.now.Add(d)
	ch := make(chan time.Time)
	close(ch)
	return ch
}

func (c *mockClock) Now() time.Time {
	return c.now
}

func assertReceive(c *gc.C, ch <-chan struct{}, what string) {
	select {
	case <-ch:
	case <-time.After(time.Second):
		c.Fatalf("timed out waiting for %s", what)
	}
}

// Below is code from github.com/juju/testing/clock.go (fortunately with
// the same copyright and license as this file), copied in rather than
// packaging juju/testing and its many (oftentimes circular) dependencies.

// timer implements a mock clock.Timer for testing purposes.
type timer struct {
	deadline time.Time
	clock    *Clock
	c        chan time.Time
	// trigger is called when the timer expires. It is
	// called with the clock mutex held and will not block.
	trigger func()
}

// Chan is part of the clock.Timer interface.
func (t *timer) Chan() <-chan time.Time {
	return t.c
}

// Clock implements a mock clock.Clock for testing purposes.
type Clock struct {
	mu           sync.Mutex
	now          time.Time
	waiting      []*timer // timers waiting to fire, sorted by deadline.
	notifyAlarms chan struct{}
}

// NewClock returns a new clock set to the supplied time. If your SUT needs to
// call After, AfterFunc, NewTimer or Timer.Reset more than 10000 times: (1)
// you have probably written a bad test; and (2) you'll need to read from the
// Alarms chan to keep the buffer clear.
func NewClock(now time.Time) *Clock {
	return &Clock{
		now:          now,
		notifyAlarms: make(chan struct{}, 10000),
	}
}

// Now is part of the clock.Clock interface.
func (clock *Clock) Now() time.Time {
	clock.mu.Lock()
	defer clock.mu.Unlock()
	return clock.now
}

// After is part of the clock.Clock interface.
func (clock *Clock) After(d time.Duration) <-chan time.Time {
	return clock.NewTimer(d).Chan()
}

func (clock *Clock) NewTimer(d time.Duration) *timer {
	c := make(chan time.Time, 1)
	return clock.addAlarm(d, c, func() {
		c <- clock.now
	})
}

func (clock *Clock) addAlarm(d time.Duration, c chan time.Time, trigger func()) *timer {
	defer clock.notifyAlarm()
	clock.mu.Lock()
	defer clock.mu.Unlock()
	t := &timer{
		c:        c,
		deadline: clock.now.Add(d),
		clock:    clock,
		trigger:  trigger,
	}
	clock.addTimer(t)
	clock.triggerAll()
	return t
}

// Advance advances the result of Now by the supplied duration, and sends
// the "current" time on all alarms which are no longer "in the future".
func (clock *Clock) Advance(d time.Duration) {
	clock.mu.Lock()
	defer clock.mu.Unlock()
	clock.now = clock.now.Add(d)
	clock.triggerAll()
}

// triggerAll triggers any alarms that are currently due and removes them
// from clock.waiting.
func (clock *Clock) triggerAll() {
	triggered := 0
	for _, t := range clock.waiting {
		if clock.now.Before(t.deadline) {
			break
		}
		t.trigger()
		triggered++
	}
	clock.waiting = clock.waiting[triggered:]
}

// reset is the underlying implementation of clock.Timer.Reset, which may be
// called by any Timer backed by this Clock.
func (clock *Clock) reset(t *timer, d time.Duration) bool {
	defer clock.notifyAlarm()
	clock.mu.Lock()
	defer clock.mu.Unlock()

	found := false
	for _, wt := range clock.waiting {
		if wt == t {
			found = true
		}
	}
	if !found {
		clock.waiting = append(clock.waiting, t)
	}
	t.deadline = clock.now.Add(d)
	sort.Sort(byDeadline(clock.waiting))
	return found
}

// stop is the underlying implementation of clock.Timer.Reset, which may be
// called by any Timer backed by this Clock.
func (clock *Clock) stop(t *timer) bool {
	clock.mu.Lock()
	defer clock.mu.Unlock()

	for i, wt := range clock.waiting {
		if wt == t {
			clock.waiting = removeFromSlice(clock.waiting, i)
			return true
		}
	}
	return false
}

// addTimer adds an alarm at time t.
func (clock *Clock) addTimer(t *timer) {
	clock.waiting = append(clock.waiting, t)
	sort.Sort(byDeadline(clock.waiting))
}

// notifyAlarm sends a value on the channel exposed by Alarms().
func (clock *Clock) notifyAlarm() {
	select {
	case clock.notifyAlarms <- struct{}{}:
	default:
		panic("alarm notification buffer full")
	}
}

// byDeadline is used to sort alarms by time.
type byDeadline []*timer

func (a byDeadline) Len() int           { return len(a) }
func (a byDeadline) Less(i, j int) bool { return a[i].deadline.Before(a[j].deadline) }
func (a byDeadline) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

// removeFromSlice removes item at the specified index from the slice.
func removeFromSlice(sl []*timer, index int) []*timer {
	return append(sl[:index], sl[index+1:]...)
}