Source file src/time/tick_test.go

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package time_test
     6  
     7  import (
     8  	"fmt"
     9  	"runtime"
    10  	"sync"
    11  	"testing"
    12  	. "time"
    13  )
    14  
    15  func TestTicker(t *testing.T) {
    16  	t.Parallel()
    17  
    18  	// We want to test that a ticker takes as much time as expected.
    19  	// Since we don't want the test to run for too long, we don't
    20  	// want to use lengthy times. This makes the test inherently flaky.
    21  	// Start with a short time, but try again with a long one if the
    22  	// first test fails.
    23  
    24  	baseCount := 10
    25  	baseDelta := 20 * Millisecond
    26  
    27  	// On Darwin ARM64 the tick frequency seems limited. Issue 35692.
    28  	if (runtime.GOOS == "darwin" || runtime.GOOS == "ios") && runtime.GOARCH == "arm64" {
    29  		// The following test will run ticker count/2 times then reset
    30  		// the ticker to double the duration for the rest of count/2.
    31  		// Since tick frequency is limited on Darwin ARM64, use even
    32  		// number to give the ticks more time to let the test pass.
    33  		// See CL 220638.
    34  		baseCount = 6
    35  		baseDelta = 100 * Millisecond
    36  	}
    37  
    38  	var errs []string
    39  	logErrs := func() {
    40  		for _, e := range errs {
    41  			t.Log(e)
    42  		}
    43  	}
    44  
    45  	for _, test := range []struct {
    46  		count int
    47  		delta Duration
    48  	}{{
    49  		count: baseCount,
    50  		delta: baseDelta,
    51  	}, {
    52  		count: 8,
    53  		delta: 1 * Second,
    54  	}} {
    55  		count, delta := test.count, test.delta
    56  		ticker := NewTicker(delta)
    57  		t0 := Now()
    58  		for range count / 2 {
    59  			<-ticker.C
    60  		}
    61  		ticker.Reset(delta * 2)
    62  		for range count - count/2 {
    63  			<-ticker.C
    64  		}
    65  		ticker.Stop()
    66  		t1 := Now()
    67  		dt := t1.Sub(t0)
    68  		target := 3 * delta * Duration(count/2)
    69  		slop := target * 3 / 10
    70  		if dt < target-slop || dt > target+slop {
    71  			errs = append(errs, fmt.Sprintf("%d %s ticks then %d %s ticks took %s, expected [%s,%s]", count/2, delta, count/2, delta*2, dt, target-slop, target+slop))
    72  			if dt > target+slop {
    73  				// System may be overloaded; sleep a bit
    74  				// in the hopes it will recover.
    75  				Sleep(Second / 2)
    76  			}
    77  			continue
    78  		}
    79  		// Now test that the ticker stopped.
    80  		Sleep(2 * delta)
    81  		select {
    82  		case <-ticker.C:
    83  			errs = append(errs, "Ticker did not shut down")
    84  			continue
    85  		default:
    86  			// ok
    87  		}
    88  
    89  		// Test passed, so all done.
    90  		if len(errs) > 0 {
    91  			t.Logf("saw %d errors, ignoring to avoid flakiness", len(errs))
    92  			logErrs()
    93  		}
    94  
    95  		return
    96  	}
    97  
    98  	t.Errorf("saw %d errors", len(errs))
    99  	logErrs()
   100  }
   101  
   102  // Issue 21874
   103  func TestTickerStopWithDirectInitialization(t *testing.T) {
   104  	c := make(chan Time)
   105  	tk := &Ticker{C: c}
   106  	tk.Stop()
   107  }
   108  
   109  // Test that a bug tearing down a ticker has been fixed. This routine should not deadlock.
   110  func TestTeardown(t *testing.T) {
   111  	t.Parallel()
   112  
   113  	Delta := 100 * Millisecond
   114  	if testing.Short() {
   115  		Delta = 20 * Millisecond
   116  	}
   117  	for range 3 {
   118  		ticker := NewTicker(Delta)
   119  		<-ticker.C
   120  		ticker.Stop()
   121  	}
   122  }
   123  
   124  // Test the Tick convenience wrapper.
   125  func TestTick(t *testing.T) {
   126  	// Test that giving a negative duration returns nil.
   127  	if got := Tick(-1); got != nil {
   128  		t.Errorf("Tick(-1) = %v; want nil", got)
   129  	}
   130  }
   131  
   132  // Test that NewTicker panics when given a duration less than zero.
   133  func TestNewTickerLtZeroDuration(t *testing.T) {
   134  	defer func() {
   135  		if err := recover(); err == nil {
   136  			t.Errorf("NewTicker(-1) should have panicked")
   137  		}
   138  	}()
   139  	NewTicker(-1)
   140  }
   141  
   142  // Test that Ticker.Reset panics when given a duration less than zero.
   143  func TestTickerResetLtZeroDuration(t *testing.T) {
   144  	defer func() {
   145  		if err := recover(); err == nil {
   146  			t.Errorf("Ticker.Reset(0) should have panicked")
   147  		}
   148  	}()
   149  	tk := NewTicker(Second)
   150  	tk.Reset(0)
   151  }
   152  
   153  func TestLongAdjustTimers(t *testing.T) {
   154  	if runtime.GOOS == "android" || runtime.GOOS == "ios" || runtime.GOOS == "plan9" {
   155  		t.Skipf("skipping on %s - too slow", runtime.GOOS)
   156  	}
   157  	if testing.Short() && runtime.NumCPU() < 2 {
   158  		t.Skipf("skipping in short mode, insufficient CPUs")
   159  	}
   160  
   161  	t.Parallel()
   162  	var wg sync.WaitGroup
   163  	defer wg.Wait()
   164  
   165  	// Build up the timer heap.
   166  	const count = 5000
   167  	wg.Add(count)
   168  	for range count {
   169  		go func() {
   170  			defer wg.Done()
   171  			Sleep(10 * Microsecond)
   172  		}()
   173  	}
   174  	for range count {
   175  		Sleep(1 * Microsecond)
   176  	}
   177  
   178  	// Give ourselves 60 seconds to complete.
   179  	// This used to reliably fail on a Mac M3 laptop,
   180  	// which needed 77 seconds.
   181  	// Trybots are slower, so it will fail even more reliably there.
   182  	// With the fix, the code runs in under a second.
   183  	done := make(chan bool)
   184  	AfterFunc(60*Second, func() { close(done) })
   185  
   186  	// Set up a queuing goroutine to ping pong through the scheduler.
   187  	inQ := make(chan func())
   188  	outQ := make(chan func())
   189  
   190  	defer close(inQ)
   191  
   192  	wg.Add(1)
   193  	go func() {
   194  		defer wg.Done()
   195  		defer close(outQ)
   196  		var q []func()
   197  		for {
   198  			var sendTo chan func()
   199  			var send func()
   200  			if len(q) > 0 {
   201  				sendTo = outQ
   202  				send = q[0]
   203  			}
   204  			select {
   205  			case sendTo <- send:
   206  				q = q[1:]
   207  			case f, ok := <-inQ:
   208  				if !ok {
   209  					return
   210  				}
   211  				q = append(q, f)
   212  			case <-done:
   213  				return
   214  			}
   215  		}
   216  	}()
   217  
   218  	for i := range 50000 {
   219  		const try = 20
   220  		for range try {
   221  			inQ <- func() {}
   222  		}
   223  		for range try {
   224  			select {
   225  			case _, ok := <-outQ:
   226  				if !ok {
   227  					t.Fatal("output channel is closed")
   228  				}
   229  			case <-After(5 * Second):
   230  				t.Fatalf("failed to read work, iteration %d", i)
   231  			case <-done:
   232  				t.Fatal("timer expired")
   233  			}
   234  		}
   235  	}
   236  }
   237  func BenchmarkTicker(b *testing.B) {
   238  	benchmark(b, func(pb *testing.PB) {
   239  		ticker := NewTicker(Nanosecond)
   240  		for pb.Next() {
   241  			<-ticker.C
   242  		}
   243  		ticker.Stop()
   244  	})
   245  }
   246  
   247  func BenchmarkTickerReset(b *testing.B) {
   248  	benchmark(b, func(pb *testing.PB) {
   249  		ticker := NewTicker(Nanosecond)
   250  		for pb.Next() {
   251  			ticker.Reset(Nanosecond * 2)
   252  		}
   253  		ticker.Stop()
   254  	})
   255  }
   256  
   257  func BenchmarkTickerResetNaive(b *testing.B) {
   258  	benchmark(b, func(pb *testing.PB) {
   259  		ticker := NewTicker(Nanosecond)
   260  		for pb.Next() {
   261  			ticker.Stop()
   262  			ticker = NewTicker(Nanosecond * 2)
   263  		}
   264  		ticker.Stop()
   265  	})
   266  }
   267  
   268  func TestTimerGC(t *testing.T) {
   269  	run := func(t *testing.T, what string, f func()) {
   270  		t.Helper()
   271  		t.Run(what, func(t *testing.T) {
   272  			t.Helper()
   273  			const N = 1e4
   274  			var stats runtime.MemStats
   275  			runtime.GC()
   276  			runtime.GC()
   277  			runtime.GC()
   278  			runtime.ReadMemStats(&stats)
   279  			before := int64(stats.Mallocs - stats.Frees)
   280  
   281  			for j := 0; j < N; j++ {
   282  				f()
   283  			}
   284  
   285  			runtime.GC()
   286  			runtime.GC()
   287  			runtime.GC()
   288  			runtime.ReadMemStats(&stats)
   289  			after := int64(stats.Mallocs - stats.Frees)
   290  
   291  			// Allow some slack, but inuse >= N means at least 1 allocation per iteration.
   292  			inuse := after - before
   293  			if inuse >= N {
   294  				t.Errorf("%s did not get GC'ed: %d allocations", what, inuse)
   295  
   296  				Sleep(1 * Second)
   297  				runtime.ReadMemStats(&stats)
   298  				after := int64(stats.Mallocs - stats.Frees)
   299  				inuse = after - before
   300  				t.Errorf("after a sleep: %d allocations", inuse)
   301  			}
   302  		})
   303  	}
   304  
   305  	run(t, "After", func() { After(Hour) })
   306  	run(t, "Tick", func() { Tick(Hour) })
   307  	run(t, "NewTimer", func() { NewTimer(Hour) })
   308  	run(t, "NewTicker", func() { NewTicker(Hour) })
   309  	run(t, "NewTimerStop", func() { NewTimer(Hour).Stop() })
   310  	run(t, "NewTickerStop", func() { NewTicker(Hour).Stop() })
   311  }
   312  
   313  func TestChan(t *testing.T) {
   314  	t.Run("Timer", func(t *testing.T) {
   315  		tim := NewTimer(10000 * Second)
   316  		testTimerChan(t, tim, tim.C)
   317  	})
   318  	t.Run("Ticker", func(t *testing.T) {
   319  		tim := &tickerTimer{Ticker: NewTicker(10000 * Second)}
   320  		testTimerChan(t, tim, tim.C)
   321  	})
   322  }
   323  
   324  type timer interface {
   325  	Stop() bool
   326  	Reset(Duration) bool
   327  }
   328  
   329  // tickerTimer is a Timer with Reset and Stop methods that return bools,
   330  // to have the same signatures as Timer.
   331  type tickerTimer struct {
   332  	*Ticker
   333  	stopped bool
   334  }
   335  
   336  func (t *tickerTimer) Stop() bool {
   337  	pending := !t.stopped
   338  	t.stopped = true
   339  	t.Ticker.Stop()
   340  	return pending
   341  }
   342  
   343  func (t *tickerTimer) Reset(d Duration) bool {
   344  	pending := !t.stopped
   345  	t.stopped = false
   346  	t.Ticker.Reset(d)
   347  	return pending
   348  }
   349  
   350  func testTimerChan(t *testing.T, tim timer, C <-chan Time) {
   351  	_, isTimer := tim.(*Timer)
   352  	isTicker := !isTimer
   353  
   354  	// Retry parameters. Enough to deflake even on slow machines.
   355  	// Windows in particular has very coarse timers so we have to
   356  	// wait 10ms just to make a timer go off.
   357  	const (
   358  		sched      = 10 * Millisecond
   359  		tries      = 100
   360  		drainTries = 5
   361  	)
   362  
   363  	noTick := func() {
   364  		t.Helper()
   365  		select {
   366  		default:
   367  		case <-C:
   368  			t.Errorf("extra tick")
   369  		}
   370  	}
   371  	assertTick := func() {
   372  		t.Helper()
   373  		select {
   374  		default:
   375  		case <-C:
   376  			return
   377  		}
   378  		for range tries {
   379  			Sleep(sched)
   380  			select {
   381  			default:
   382  			case <-C:
   383  				return
   384  			}
   385  		}
   386  		t.Errorf("missing tick")
   387  	}
   388  
   389  	// Test simple stop; timer never in heap.
   390  	tim.Stop()
   391  	noTick()
   392  
   393  	// Test modify of timer not in heap.
   394  	tim.Reset(10000 * Second)
   395  	noTick()
   396  
   397  	// Test modify of timer in heap.
   398  	tim.Reset(1)
   399  	Sleep(sched)
   400  	if l, c := len(C), cap(C); l != 0 || c != 0 {
   401  		t.Fatalf("len(C), cap(C) = %d, %d, want 0, 0", l, c)
   402  	}
   403  	assertTick()
   404  
   405  	// Sleep long enough that a second tick must happen if this is a ticker.
   406  	// Test that Reset does not lose the tick that should have happened.
   407  	Sleep(sched)
   408  	tim.Reset(10000 * Second)
   409  	noTick()
   410  
   411  	notDone := func(done chan bool) {
   412  		t.Helper()
   413  		select {
   414  		default:
   415  		case <-done:
   416  			t.Fatalf("early done")
   417  		}
   418  	}
   419  
   420  	waitDone := func(done chan bool) {
   421  		t.Helper()
   422  		for range tries {
   423  			Sleep(sched)
   424  			select {
   425  			case <-done:
   426  				return
   427  			default:
   428  			}
   429  		}
   430  		t.Fatalf("never got done")
   431  	}
   432  
   433  	// Reset timer in heap (already reset above, but just in case).
   434  	tim.Reset(10000 * Second)
   435  
   436  	// Test stop while timer in heap (because goroutine is blocked on <-C).
   437  	done := make(chan bool)
   438  	notDone(done)
   439  	go func() {
   440  		<-C
   441  		close(done)
   442  	}()
   443  	Sleep(sched)
   444  	notDone(done)
   445  
   446  	// Test reset far away while timer in heap.
   447  	tim.Reset(20000 * Second)
   448  	Sleep(sched)
   449  	notDone(done)
   450  
   451  	// Test imminent reset while in heap.
   452  	tim.Reset(1)
   453  	waitDone(done)
   454  
   455  	// If this is a ticker, another tick should have come in already
   456  	// (they are 1ns apart). If a timer, it should have stopped.
   457  	if isTicker {
   458  		assertTick()
   459  	} else {
   460  		noTick()
   461  	}
   462  
   463  	tim.Stop()
   464  	noTick()
   465  
   466  	// Again using select and with two goroutines waiting.
   467  	tim.Reset(10000 * Second)
   468  	done = make(chan bool, 2)
   469  	done1 := make(chan bool)
   470  	done2 := make(chan bool)
   471  	stop := make(chan bool)
   472  	go func() {
   473  		select {
   474  		case <-C:
   475  			done <- true
   476  		case <-stop:
   477  		}
   478  		close(done1)
   479  	}()
   480  	go func() {
   481  		select {
   482  		case <-C:
   483  			done <- true
   484  		case <-stop:
   485  		}
   486  		close(done2)
   487  	}()
   488  	Sleep(sched)
   489  	notDone(done)
   490  	tim.Reset(sched / 2)
   491  	Sleep(sched)
   492  	waitDone(done)
   493  	tim.Stop()
   494  	close(stop)
   495  	waitDone(done1)
   496  	waitDone(done2)
   497  	if isTicker {
   498  		// extra send might have sent done again
   499  		// (handled by buffering done above).
   500  		select {
   501  		default:
   502  		case <-done:
   503  		}
   504  		// extra send after that might have filled C.
   505  		select {
   506  		default:
   507  		case <-C:
   508  		}
   509  	}
   510  	notDone(done)
   511  
   512  	// Test enqueueTimerChan when timer is stopped.
   513  	stop = make(chan bool)
   514  	done = make(chan bool, 2)
   515  	for range 2 {
   516  		go func() {
   517  			select {
   518  			case <-C:
   519  				panic("unexpected data")
   520  			case <-stop:
   521  			}
   522  			done <- true
   523  		}()
   524  	}
   525  	Sleep(sched)
   526  	close(stop)
   527  	waitDone(done)
   528  	waitDone(done)
   529  
   530  	// Test that Stop and Reset block old values from being received.
   531  	// (Proposal go.dev/issue/37196.)
   532  	tim.Reset(1)
   533  	Sleep(10 * Millisecond)
   534  	if pending := tim.Stop(); pending != true {
   535  		t.Errorf("tim.Stop() = %v, want true", pending)
   536  	}
   537  	noTick()
   538  
   539  	tim.Reset(Hour)
   540  	noTick()
   541  	if pending := tim.Reset(1); pending != true {
   542  		t.Errorf("tim.Stop() = %v, want true", pending)
   543  	}
   544  	assertTick()
   545  	Sleep(10 * Millisecond)
   546  	if isTicker {
   547  		assertTick()
   548  		Sleep(10 * Millisecond)
   549  	} else {
   550  		noTick()
   551  	}
   552  	if pending, want := tim.Reset(Hour), isTicker; pending != want {
   553  		t.Errorf("tim.Stop() = %v, want %v", pending, want)
   554  	}
   555  	noTick()
   556  }
   557  
   558  func TestManualTicker(t *testing.T) {
   559  	// Code should not do this, but some old code dating to Go 1.9 does.
   560  	// Make sure this doesn't crash.
   561  	// See go.dev/issue/21874.
   562  	c := make(chan Time)
   563  	tick := &Ticker{C: c}
   564  	tick.Stop()
   565  }
   566  
   567  func TestAfterTimes(t *testing.T) {
   568  	t.Parallel()
   569  	// Using After(10ms) but waiting for 500ms to read the channel
   570  	// should produce a time from start+10ms, not start+500ms.
   571  	// Make sure it does.
   572  	// To avoid flakes due to very long scheduling delays,
   573  	// require 10 failures in a row before deciding something is wrong.
   574  	for range 10 {
   575  		start := Now()
   576  		c := After(10 * Millisecond)
   577  		Sleep(500 * Millisecond)
   578  		dt := (<-c).Sub(start)
   579  		if dt < 400*Millisecond {
   580  			return
   581  		}
   582  		t.Logf("After(10ms) time is +%v, want <400ms", dt)
   583  	}
   584  	t.Errorf("not working")
   585  }
   586  
   587  func TestTickTimes(t *testing.T) {
   588  	t.Parallel()
   589  	// See comment in TestAfterTimes
   590  	for range 10 {
   591  		start := Now()
   592  		c := Tick(10 * Millisecond)
   593  		Sleep(500 * Millisecond)
   594  		dt := (<-c).Sub(start)
   595  		if dt < 400*Millisecond {
   596  			return
   597  		}
   598  		t.Logf("Tick(10ms) time is +%v, want <400ms", dt)
   599  	}
   600  	t.Errorf("not working")
   601  }
   602  

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