singleflight/singleflight_test.go - sync - Git at Google

 // Copyright 2013 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 package singleflight

 import (
 	"bytes"
 	"errors"
 	"fmt"
 	"os"
 	"os/exec"
 	"runtime"
 	"runtime/debug"
 	"strings"
 	"sync"
 	"sync/atomic"
 	"testing"
 	"time"
 )

 type errValue struct{}

 func (err *errValue) Error() string {
 	return "error value"
 }

 func TestPanicErrorUnwrap(t *testing.T) {
 	t.Parallel()

 	testCases := []struct {
 		name             string
 		panicValue       interface{}
 		wrappedErrorType bool
 	}{
 		{
 			name:             "panicError wraps non-error type",
 			panicValue:       &panicError{value: "string value"},
 			wrappedErrorType: false,
 		},
 		{
 			name:             "panicError wraps error type",
 			panicValue:       &panicError{value: new(errValue)},
 			wrappedErrorType: false,
 		},
 	}

 	for _, tc := range testCases {
 		tc := tc

 		t.Run(tc.name, func(t *testing.T) {
 			t.Parallel()

 			var recovered interface{}

 			group := &Group{}

 			func() {
 				defer func() {
 					recovered = recover()
 					t.Logf("after panic(%#v) in group.Do, recovered %#v", tc.panicValue, recovered)
 				}()

 				_, _, _ = group.Do(tc.name, func() (interface{}, error) {
 					panic(tc.panicValue)
 				})
 			}()

 			if recovered == nil {
 				t.Fatal("expected a non-nil panic value")
 			}

 			err, ok := recovered.(error)
 			if !ok {
 				t.Fatalf("recovered non-error type: %T", recovered)
 			}

 			if !errors.Is(err, new(errValue)) && tc.wrappedErrorType {
 				t.Errorf("unexpected wrapped error type %T; want %T", err, new(errValue))
 			}
 		})
 	}
 }

 func TestDo(t *testing.T) {
 	var g Group
 	v, err, _ := g.Do("key", func() (interface{}, error) {
 		return "bar", nil
 	})
 	if got, want := fmt.Sprintf("%v (%T)", v, v), "bar (string)"; got != want {
 		t.Errorf("Do = %v; want %v", got, want)
 	}
 	if err != nil {
 		t.Errorf("Do error = %v", err)
 	}
 }

 func TestDoErr(t *testing.T) {
 	var g Group
 	someErr := errors.New("Some error")
 	v, err, _ := g.Do("key", func() (interface{}, error) {
 		return nil, someErr
 	})
 	if err != someErr {
 		t.Errorf("Do error = %v; want someErr %v", err, someErr)
 	}
 	if v != nil {
 		t.Errorf("unexpected non-nil value %#v", v)
 	}
 }

 func TestDoDupSuppress(t *testing.T) {
 	var g Group
 	var wg1, wg2 sync.WaitGroup
 	c := make(chan string, 1)
 	var calls int32
 	fn := func() (interface{}, error) {
 		if atomic.AddInt32(&calls, 1) == 1 {
 			// First invocation.
 			wg1.Done()
 		}
 		v := <-c
 		c <- v // pump; make available for any future calls

 		time.Sleep(10 * time.Millisecond) // let more goroutines enter Do

 		return v, nil
 	}

 	const n = 10
 	wg1.Add(1)
 	for i := 0; i < n; i++ {
 		wg1.Add(1)
 		wg2.Add(1)
 		go func() {
 			defer wg2.Done()
 			wg1.Done()
 			v, err, _ := g.Do("key", fn)
 			if err != nil {
 				t.Errorf("Do error: %v", err)
 				return
 			}
 			if s, _ := v.(string); s != "bar" {
 				t.Errorf("Do = %T %v; want %q", v, v, "bar")
 			}
 		}()
 	}
 	wg1.Wait()
 	// At least one goroutine is in fn now and all of them have at
 	// least reached the line before the Do.
 	c <- "bar"
 	wg2.Wait()
 	if got := atomic.LoadInt32(&calls); got <= 0 || got >= n {
 		t.Errorf("number of calls = %d; want over 0 and less than %d", got, n)
 	}
 }

 // Test that singleflight behaves correctly after Forget called.
 // See https://github.com/golang/go/issues/31420
 func TestForget(t *testing.T) {
 	var g Group

 	var (
 		firstStarted  = make(chan struct{})
 		unblockFirst  = make(chan struct{})
 		firstFinished = make(chan struct{})
 	)

 	go func() {
 		g.Do("key", func() (i interface{}, e error) {
 			close(firstStarted)
 			<-unblockFirst
 			close(firstFinished)
 			return
 		})
 	}()
 	<-firstStarted
 	g.Forget("key")

 	unblockSecond := make(chan struct{})
 	secondResult := g.DoChan("key", func() (i interface{}, e error) {
 		<-unblockSecond
 		return 2, nil
 	})

 	close(unblockFirst)
 	<-firstFinished

 	thirdResult := g.DoChan("key", func() (i interface{}, e error) {
 		return 3, nil
 	})

 	close(unblockSecond)
 	<-secondResult
 	r := <-thirdResult
 	if r.Val != 2 {
 		t.Errorf("We should receive result produced by second call, expected: 2, got %d", r.Val)
 	}
 }

 func TestDoChan(t *testing.T) {
 	var g Group
 	ch := g.DoChan("key", func() (interface{}, error) {
 		return "bar", nil
 	})

 	res := <-ch
 	v := res.Val
 	err := res.Err
 	if got, want := fmt.Sprintf("%v (%T)", v, v), "bar (string)"; got != want {
 		t.Errorf("Do = %v; want %v", got, want)
 	}
 	if err != nil {
 		t.Errorf("Do error = %v", err)
 	}
 }

 // Test singleflight behaves correctly after Do panic.
 // See https://github.com/golang/go/issues/41133
 func TestPanicDo(t *testing.T) {
 	var g Group
 	fn := func() (interface{}, error) {
 		panic("invalid memory address or nil pointer dereference")
 	}

 	const n = 5
 	waited := int32(n)
 	panicCount := int32(0)
 	done := make(chan struct{})
 	for i := 0; i < n; i++ {
 		go func() {
 			defer func() {
 				if err := recover(); err != nil {
 					t.Logf("Got panic: %v\n%s", err, debug.Stack())
 					atomic.AddInt32(&panicCount, 1)
 				}

 				if atomic.AddInt32(&waited, -1) == 0 {
 					close(done)
 				}
 			}()

 			g.Do("key", fn)
 		}()
 	}

 	select {
 	case <-done:
 		if panicCount != n {
 			t.Errorf("Expect %d panic, but got %d", n, panicCount)
 		}
 	case <-time.After(time.Second):
 		t.Fatalf("Do hangs")
 	}
 }

 func TestGoexitDo(t *testing.T) {
 	var g Group
 	fn := func() (interface{}, error) {
 		runtime.Goexit()
 		return nil, nil
 	}

 	const n = 5
 	waited := int32(n)
 	done := make(chan struct{})
 	for i := 0; i < n; i++ {
 		go func() {
 			var err error
 			defer func() {
 				if err != nil {
 					t.Errorf("Error should be nil, but got: %v", err)
 				}
 				if atomic.AddInt32(&waited, -1) == 0 {
 					close(done)
 				}
 			}()
 			_, err, _ = g.Do("key", fn)
 		}()
 	}

 	select {
 	case <-done:
 	case <-time.After(time.Second):
 		t.Fatalf("Do hangs")
 	}
 }

 func executable(t testing.TB) string {
 	exe, err := os.Executable()
 	if err != nil {
 		t.Skipf("skipping: test executable not found")
 	}

 	// Control case: check whether exec.Command works at all.
 	// (For example, it might fail with a permission error on iOS.)
 	cmd := exec.Command(exe, "-test.list=^$")
 	cmd.Env = []string{}
 	if err := cmd.Run(); err != nil {
 		t.Skipf("skipping: exec appears not to work on %s: %v", runtime.GOOS, err)
 	}

 	return exe
 }

 func TestPanicDoChan(t *testing.T) {
 	if os.Getenv("TEST_PANIC_DOCHAN") != "" {
 		defer func() {
 			recover()
 		}()

 		g := new(Group)
 		ch := g.DoChan("", func() (interface{}, error) {
 			panic("Panicking in DoChan")
 		})
 		<-ch
 		t.Fatalf("DoChan unexpectedly returned")
 	}

 	t.Parallel()

 	cmd := exec.Command(executable(t), "-test.run="+t.Name(), "-test.v")
 	cmd.Env = append(os.Environ(), "TEST_PANIC_DOCHAN=1")
 	out := new(bytes.Buffer)
 	cmd.Stdout = out
 	cmd.Stderr = out
 	if err := cmd.Start(); err != nil {
 		t.Fatal(err)
 	}

 	err := cmd.Wait()
 	t.Logf("%s:\n%s", strings.Join(cmd.Args, " "), out)
 	if err == nil {
 		t.Errorf("Test subprocess passed; want a crash due to panic in DoChan")
 	}
 	if bytes.Contains(out.Bytes(), []byte("DoChan unexpectedly")) {
 		t.Errorf("Test subprocess failed with an unexpected failure mode.")
 	}
 	if !bytes.Contains(out.Bytes(), []byte("Panicking in DoChan")) {
 		t.Errorf("Test subprocess failed, but the crash isn't caused by panicking in DoChan")
 	}
 }

 func TestPanicDoSharedByDoChan(t *testing.T) {
 	if os.Getenv("TEST_PANIC_DOCHAN") != "" {
 		blocked := make(chan struct{})
 		unblock := make(chan struct{})

 		g := new(Group)
 		go func() {
 			defer func() {
 				recover()
 			}()
 			g.Do("", func() (interface{}, error) {
 				close(blocked)
 				<-unblock
 				panic("Panicking in Do")
 			})
 		}()

 		<-blocked
 		ch := g.DoChan("", func() (interface{}, error) {
 			panic("DoChan unexpectedly executed callback")
 		})
 		close(unblock)
 		<-ch
 		t.Fatalf("DoChan unexpectedly returned")
 	}

 	t.Parallel()

 	cmd := exec.Command(executable(t), "-test.run="+t.Name(), "-test.v")
 	cmd.Env = append(os.Environ(), "TEST_PANIC_DOCHAN=1")
 	out := new(bytes.Buffer)
 	cmd.Stdout = out
 	cmd.Stderr = out
 	if err := cmd.Start(); err != nil {
 		t.Fatal(err)
 	}

 	err := cmd.Wait()
 	t.Logf("%s:\n%s", strings.Join(cmd.Args, " "), out)
 	if err == nil {
 		t.Errorf("Test subprocess passed; want a crash due to panic in Do shared by DoChan")
 	}
 	if bytes.Contains(out.Bytes(), []byte("DoChan unexpectedly")) {
 		t.Errorf("Test subprocess failed with an unexpected failure mode.")
 	}
 	if !bytes.Contains(out.Bytes(), []byte("Panicking in Do")) {
 		t.Errorf("Test subprocess failed, but the crash isn't caused by panicking in Do")
 	}
 }

 func ExampleGroup() {
 	g := new(Group)

 	block := make(chan struct{})
 	res1c := g.DoChan("key", func() (interface{}, error) {
 		<-block
 		return "func 1", nil
 	})
 	res2c := g.DoChan("key", func() (interface{}, error) {
 		<-block
 		return "func 2", nil
 	})
 	close(block)

 	res1 := <-res1c
 	res2 := <-res2c

 	// Results are shared by functions executed with duplicate keys.
 	fmt.Println("Shared:", res2.Shared)
 	// Only the first function is executed: it is registered and started with "key",
 	// and doesn't complete before the second function is registered with a duplicate key.
 	fmt.Println("Equal results:", res1.Val.(string) == res2.Val.(string))
 	fmt.Println("Result:", res1.Val)

 	// Output:
 	// Shared: true
 	// Equal results: true
 	// Result: func 1
 }
	// Copyright 2013 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	package singleflight

	import (
	"bytes"
	"errors"
	"fmt"
	"os"
	"os/exec"
	"runtime"
	"runtime/debug"
	"strings"
	"sync"
	"sync/atomic"
	"testing"
	"time"
	)

	type errValue struct{}

	func (err *errValue) Error() string {
	return "error value"
	}

	func TestPanicErrorUnwrap(t *testing.T) {
	t.Parallel()

	testCases := []struct {
	name string
	panicValue interface{}
	wrappedErrorType bool
	}{
	{
	name: "panicError wraps non-error type",
	panicValue: &panicError{value: "string value"},
	wrappedErrorType: false,
	},
	{
	name: "panicError wraps error type",
	panicValue: &panicError{value: new(errValue)},
	wrappedErrorType: false,
	},
	}

	for _, tc := range testCases {
	tc := tc

	t.Run(tc.name, func(t *testing.T) {
	t.Parallel()

	var recovered interface{}

	group := &Group{}

	func() {
	defer func() {
	recovered = recover()
	t.Logf("after panic(%#v) in group.Do, recovered %#v", tc.panicValue, recovered)
	}()

	_, _, _ = group.Do(tc.name, func() (interface{}, error) {
	panic(tc.panicValue)
	})
	}()

	if recovered == nil {
	t.Fatal("expected a non-nil panic value")
	}

	err, ok := recovered.(error)
	if !ok {
	t.Fatalf("recovered non-error type: %T", recovered)
	}

	if !errors.Is(err, new(errValue)) && tc.wrappedErrorType {
	t.Errorf("unexpected wrapped error type %T; want %T", err, new(errValue))
	}
	})
	}
	}

	func TestDo(t *testing.T) {
	var g Group
	v, err, _ := g.Do("key", func() (interface{}, error) {
	return "bar", nil
	})
	if got, want := fmt.Sprintf("%v (%T)", v, v), "bar (string)"; got != want {
	t.Errorf("Do = %v; want %v", got, want)
	}
	if err != nil {
	t.Errorf("Do error = %v", err)
	}
	}

	func TestDoErr(t *testing.T) {
	var g Group
	someErr := errors.New("Some error")
	v, err, _ := g.Do("key", func() (interface{}, error) {
	return nil, someErr
	})
	if err != someErr {
	t.Errorf("Do error = %v; want someErr %v", err, someErr)
	}
	if v != nil {
	t.Errorf("unexpected non-nil value %#v", v)
	}
	}

	func TestDoDupSuppress(t *testing.T) {
	var g Group
	var wg1, wg2 sync.WaitGroup
	c := make(chan string, 1)
	var calls int32
	fn := func() (interface{}, error) {
	if atomic.AddInt32(&calls, 1) == 1 {
	// First invocation.
	wg1.Done()
	}
	v := <-c
	c <- v // pump; make available for any future calls

	time.Sleep(10 * time.Millisecond) // let more goroutines enter Do

	return v, nil
	}

	const n = 10
	wg1.Add(1)
	for i := 0; i < n; i++ {
	wg1.Add(1)
	wg2.Add(1)
	go func() {
	defer wg2.Done()
	wg1.Done()
	v, err, _ := g.Do("key", fn)
	if err != nil {
	t.Errorf("Do error: %v", err)
	return
	}
	if s, _ := v.(string); s != "bar" {
	t.Errorf("Do = %T %v; want %q", v, v, "bar")
	}
	}()
	}
	wg1.Wait()
	// At least one goroutine is in fn now and all of them have at
	// least reached the line before the Do.
	c <- "bar"
	wg2.Wait()
	if got := atomic.LoadInt32(&calls); got <= 0 \|\| got >= n {
	t.Errorf("number of calls = %d; want over 0 and less than %d", got, n)
	}
	}

	// Test that singleflight behaves correctly after Forget called.
	// See https://github.com/golang/go/issues/31420
	func TestForget(t *testing.T) {
	var g Group

	var (
	firstStarted = make(chan struct{})
	unblockFirst = make(chan struct{})
	firstFinished = make(chan struct{})
	)

	go func() {
	g.Do("key", func() (i interface{}, e error) {
	close(firstStarted)
	<-unblockFirst
	close(firstFinished)
	return
	})
	}()
	<-firstStarted
	g.Forget("key")

	unblockSecond := make(chan struct{})
	secondResult := g.DoChan("key", func() (i interface{}, e error) {
	<-unblockSecond
	return 2, nil
	})

	close(unblockFirst)
	<-firstFinished

	thirdResult := g.DoChan("key", func() (i interface{}, e error) {
	return 3, nil
	})

	close(unblockSecond)
	<-secondResult
	r := <-thirdResult
	if r.Val != 2 {
	t.Errorf("We should receive result produced by second call, expected: 2, got %d", r.Val)
	}
	}

	func TestDoChan(t *testing.T) {
	var g Group
	ch := g.DoChan("key", func() (interface{}, error) {
	return "bar", nil
	})

	res := <-ch
	v := res.Val
	err := res.Err
	if got, want := fmt.Sprintf("%v (%T)", v, v), "bar (string)"; got != want {
	t.Errorf("Do = %v; want %v", got, want)
	}
	if err != nil {
	t.Errorf("Do error = %v", err)
	}
	}

	// Test singleflight behaves correctly after Do panic.
	// See https://github.com/golang/go/issues/41133
	func TestPanicDo(t *testing.T) {
	var g Group
	fn := func() (interface{}, error) {
	panic("invalid memory address or nil pointer dereference")
	}

	const n = 5
	waited := int32(n)
	panicCount := int32(0)
	done := make(chan struct{})
	for i := 0; i < n; i++ {
	go func() {
	defer func() {
	if err := recover(); err != nil {
	t.Logf("Got panic: %v\n%s", err, debug.Stack())
	atomic.AddInt32(&panicCount, 1)
	}

	if atomic.AddInt32(&waited, -1) == 0 {
	close(done)
	}
	}()

	g.Do("key", fn)
	}()
	}

	select {
	case <-done:
	if panicCount != n {
	t.Errorf("Expect %d panic, but got %d", n, panicCount)
	}
	case <-time.After(time.Second):
	t.Fatalf("Do hangs")
	}
	}

	func TestGoexitDo(t *testing.T) {
	var g Group
	fn := func() (interface{}, error) {
	runtime.Goexit()
	return nil, nil
	}

	const n = 5
	waited := int32(n)
	done := make(chan struct{})
	for i := 0; i < n; i++ {
	go func() {
	var err error
	defer func() {
	if err != nil {
	t.Errorf("Error should be nil, but got: %v", err)
	}
	if atomic.AddInt32(&waited, -1) == 0 {
	close(done)
	}
	}()
	_, err, _ = g.Do("key", fn)
	}()
	}

	select {
	case <-done:
	case <-time.After(time.Second):
	t.Fatalf("Do hangs")
	}
	}

	func executable(t testing.TB) string {
	exe, err := os.Executable()
	if err != nil {
	t.Skipf("skipping: test executable not found")
	}

	// Control case: check whether exec.Command works at all.
	// (For example, it might fail with a permission error on iOS.)
	cmd := exec.Command(exe, "-test.list=^$")
	cmd.Env = []string{}
	if err := cmd.Run(); err != nil {
	t.Skipf("skipping: exec appears not to work on %s: %v", runtime.GOOS, err)
	}

	return exe
	}

	func TestPanicDoChan(t *testing.T) {
	if os.Getenv("TEST_PANIC_DOCHAN") != "" {
	defer func() {
	recover()
	}()

	g := new(Group)
	ch := g.DoChan("", func() (interface{}, error) {
	panic("Panicking in DoChan")
	})
	<-ch
	t.Fatalf("DoChan unexpectedly returned")
	}

	t.Parallel()

	cmd := exec.Command(executable(t), "-test.run="+t.Name(), "-test.v")
	cmd.Env = append(os.Environ(), "TEST_PANIC_DOCHAN=1")
	out := new(bytes.Buffer)
	cmd.Stdout = out
	cmd.Stderr = out
	if err := cmd.Start(); err != nil {
	t.Fatal(err)
	}

	err := cmd.Wait()
	t.Logf("%s:\n%s", strings.Join(cmd.Args, " "), out)
	if err == nil {
	t.Errorf("Test subprocess passed; want a crash due to panic in DoChan")
	}
	if bytes.Contains(out.Bytes(), []byte("DoChan unexpectedly")) {
	t.Errorf("Test subprocess failed with an unexpected failure mode.")
	}
	if !bytes.Contains(out.Bytes(), []byte("Panicking in DoChan")) {
	t.Errorf("Test subprocess failed, but the crash isn't caused by panicking in DoChan")
	}
	}

	func TestPanicDoSharedByDoChan(t *testing.T) {
	if os.Getenv("TEST_PANIC_DOCHAN") != "" {
	blocked := make(chan struct{})
	unblock := make(chan struct{})

	g := new(Group)
	go func() {
	defer func() {
	recover()
	}()
	g.Do("", func() (interface{}, error) {
	close(blocked)
	<-unblock
	panic("Panicking in Do")
	})
	}()

	<-blocked
	ch := g.DoChan("", func() (interface{}, error) {
	panic("DoChan unexpectedly executed callback")
	})
	close(unblock)
	<-ch
	t.Fatalf("DoChan unexpectedly returned")
	}

	t.Parallel()

	cmd := exec.Command(executable(t), "-test.run="+t.Name(), "-test.v")
	cmd.Env = append(os.Environ(), "TEST_PANIC_DOCHAN=1")
	out := new(bytes.Buffer)
	cmd.Stdout = out
	cmd.Stderr = out
	if err := cmd.Start(); err != nil {
	t.Fatal(err)
	}

	err := cmd.Wait()
	t.Logf("%s:\n%s", strings.Join(cmd.Args, " "), out)
	if err == nil {
	t.Errorf("Test subprocess passed; want a crash due to panic in Do shared by DoChan")
	}
	if bytes.Contains(out.Bytes(), []byte("DoChan unexpectedly")) {
	t.Errorf("Test subprocess failed with an unexpected failure mode.")
	}
	if !bytes.Contains(out.Bytes(), []byte("Panicking in Do")) {
	t.Errorf("Test subprocess failed, but the crash isn't caused by panicking in Do")
	}
	}

	func ExampleGroup() {
	g := new(Group)

	block := make(chan struct{})
	res1c := g.DoChan("key", func() (interface{}, error) {
	<-block
	return "func 1", nil
	})
	res2c := g.DoChan("key", func() (interface{}, error) {
	<-block
	return "func 2", nil
	})
	close(block)

	res1 := <-res1c
	res2 := <-res2c

	// Results are shared by functions executed with duplicate keys.
	fmt.Println("Shared:", res2.Shared)
	// Only the first function is executed: it is registered and started with "key",
	// and doesn't complete before the second function is registered with a duplicate key.
	fmt.Println("Equal results:", res1.Val.(string) == res2.Val.(string))
	fmt.Println("Result:", res1.Val)

	// Output:
	// Shared: true
	// Equal results: true
	// Result: func 1
	}