add retry codes

README.md

@@ -1,6 +1,6 @@
 # Go语言设计模式示例集合(Go Patterns Examples)
 
-**包括了[go-patterns](https://github.com/tmrts/go-patterns) 和[golang-design-pattern](https://github.com/senghoo/golang-design-pattern)中的全部模式！！！**
+**包括了[go-patterns](https://github.com/tmrts/go-patterns) 和[golang-design-pattern](https://github.com/senghoo/golang-design-pattern)中的全部模式**
 
 目前包括了**39种Go中常用的、面向工程化和最佳实践的模式/套路**，自然也包含常见的23种设计模式,重点是这里全部是例子、通俗易懂，甚至每个模式下的例子，改一下名字，稍微再增加几行代码就可以直接用在项目和工程中了。
 
@@ -80,6 +80,8 @@
 
 [design_pattern](http://c.biancheng.net/design_pattern)
 
+[go-resiliency](https://github.com/eapache/go-resiliency)
+
 
 ## 更多
 

gomore/retrier/backoffs.go

@@ -0,0 +1,24 @@
+package retrier
+
+import "time"
+
+// ConstantBackoff generates a simple back-off strategy of retrying 'n' times, and waiting 'amount' time after each one.
+func ConstantBackoff(n int, amount time.Duration) []time.Duration {
+	ret := make([]time.Duration, n)
+	for i := range ret {
+		ret[i] = amount
+	}
+	return ret
+}
+
+// ExponentialBackoff generates a simple back-off strategy of retrying 'n' times, and doubling the amount of
+// time waited after each one.
+func ExponentialBackoff(n int, initialAmount time.Duration) []time.Duration {
+	ret := make([]time.Duration, n)
+	next := initialAmount
+	for i := range ret {
+		ret[i] = next
+		next *= 2
+	}
+	return ret
+}

gomore/retrier/backoffs_test.go

@@ -0,0 +1,55 @@
+package retrier
+
+import (
+	"testing"
+	"time"
+)
+
+func TestConstantBackoff(t *testing.T) {
+	b := ConstantBackoff(1, 10*time.Millisecond)
+	if len(b) != 1 {
+		t.Error("incorrect length")
+	}
+	for i := range b {
+		if b[i] != 10*time.Millisecond {
+			t.Error("incorrect value at", i)
+		}
+	}
+
+	b = ConstantBackoff(10, 250*time.Hour)
+	if len(b) != 10 {
+		t.Error("incorrect length")
+	}
+	for i := range b {
+		if b[i] != 250*time.Hour {
+			t.Error("incorrect value at", i)
+		}
+	}
+}
+
+func TestExponentialBackoff(t *testing.T) {
+	b := ExponentialBackoff(1, 10*time.Millisecond)
+	if len(b) != 1 {
+		t.Error("incorrect length")
+	}
+	if b[0] != 10*time.Millisecond {
+		t.Error("incorrect value")
+	}
+
+	b = ExponentialBackoff(4, 1*time.Minute)
+	if len(b) != 4 {
+		t.Error("incorrect length")
+	}
+	if b[0] != 1*time.Minute {
+		t.Error("incorrect value")
+	}
+	if b[1] != 2*time.Minute {
+		t.Error("incorrect value")
+	}
+	if b[2] != 4*time.Minute {
+		t.Error("incorrect value")
+	}
+	if b[3] != 8*time.Minute {
+		t.Error("incorrect value")
+	}
+}

gomore/retrier/classifier.go

@@ -0,0 +1,66 @@
+package retrier
+
+// Action is the type returned by a Classifier to indicate how the Retrier should proceed.
+type Action int
+
+const (
+	Succeed Action = iota // Succeed indicates the Retrier should treat this value as a success.
+	Fail                  // Fail indicates the Retrier should treat this value as a hard failure and not retry.
+	Retry                 // Retry indicates the Retrier should treat this value as a soft failure and retry.
+)
+
+// Classifier is the interface implemented by anything that can classify Errors for a Retrier.
+type Classifier interface {
+	Classify(error) Action
+}
+
+// DefaultClassifier classifies errors in the simplest way possible. If
+// the error is nil, it returns Succeed, otherwise it returns Retry.
+type DefaultClassifier struct{}
+
+// Classify implements the Classifier interface.
+func (c DefaultClassifier) Classify(err error) Action {
+	if err == nil {
+		return Succeed
+	}
+
+	return Retry
+}
+
+// WhitelistClassifier classifies errors based on a whitelist. If the error is nil, it
+// returns Succeed; if the error is in the whitelist, it returns Retry; otherwise, it returns Fail.
+type WhitelistClassifier []error
+
+// Classify implements the Classifier interface.
+func (list WhitelistClassifier) Classify(err error) Action {
+	if err == nil {
+		return Succeed
+	}
+
+	for _, pass := range list {
+		if err == pass {
+			return Retry
+		}
+	}
+
+	return Fail
+}
+
+// BlacklistClassifier classifies errors based on a blacklist. If the error is nil, it
+// returns Succeed; if the error is in the blacklist, it returns Fail; otherwise, it returns Retry.
+type BlacklistClassifier []error
+
+// Classify implements the Classifier interface.
+func (list BlacklistClassifier) Classify(err error) Action {
+	if err == nil {
+		return Succeed
+	}
+
+	for _, pass := range list {
+		if err == pass {
+			return Fail
+		}
+	}
+
+	return Retry
+}

gomore/retrier/classifier_test.go

@@ -0,0 +1,66 @@
+package retrier
+
+import (
+	"errors"
+	"testing"
+)
+
+var (
+	errFoo = errors.New("FOO")
+	errBar = errors.New("BAR")
+	errBaz = errors.New("BAZ")
+)
+
+func TestDefaultClassifier(t *testing.T) {
+	c := DefaultClassifier{}
+
+	if c.Classify(nil) != Succeed {
+		t.Error("default misclassified nil")
+	}
+
+	if c.Classify(errFoo) != Retry {
+		t.Error("default misclassified foo")
+	}
+	if c.Classify(errBar) != Retry {
+		t.Error("default misclassified bar")
+	}
+	if c.Classify(errBaz) != Retry {
+		t.Error("default misclassified baz")
+	}
+}
+
+func TestWhitelistClassifier(t *testing.T) {
+	c := WhitelistClassifier{errFoo, errBar}
+
+	if c.Classify(nil) != Succeed {
+		t.Error("whitelist misclassified nil")
+	}
+
+	if c.Classify(errFoo) != Retry {
+		t.Error("whitelist misclassified foo")
+	}
+	if c.Classify(errBar) != Retry {
+		t.Error("whitelist misclassified bar")
+	}
+	if c.Classify(errBaz) != Fail {
+		t.Error("whitelist misclassified baz")
+	}
+}
+
+func TestBlacklistClassifier(t *testing.T) {
+	c := BlacklistClassifier{errBar}
+
+	if c.Classify(nil) != Succeed {
+		t.Error("blacklist misclassified nil")
+	}
+
+	if c.Classify(errFoo) != Retry {
+		t.Error("blacklist misclassified foo")
+	}
+	if c.Classify(errBar) != Fail {
+		t.Error("blacklist misclassified bar")
+	}
+	if c.Classify(errBaz) != Retry {
+		t.Error("blacklist misclassified baz")
+	}
+}

gomore/retrier/retrier.go

@@ -0,0 +1,97 @@
+// Package retrier implements the "retriable" resiliency pattern for Go.
+package retrier
+
+import (
+	"context"
+	"math/rand"
+	"sync"
+	"time"
+)
+
+// Retrier implements the "retriable" resiliency pattern, abstracting out the process of retrying a failed action
+// a certain number of times with an optional back-off between each retry.
+type Retrier struct {
+	backoff []time.Duration
+	class   Classifier
+	jitter  float64
+	rand    *rand.Rand
+	randMu  sync.Mutex
+}
+
+// New constructs a Retrier with the given backoff pattern and classifier. The length of the backoff pattern
+// indicates how many times an action will be retried, and the value at each index indicates the amount of time
+// waited before each subsequent retry. The classifier is used to determine which errors should be retried and
+// which should cause the retrier to fail fast. The DefaultClassifier is used if nil is passed.
+func New(backoff []time.Duration, class Classifier) *Retrier {
+	if class == nil {
+		class = DefaultClassifier{}
+	}
+
+	return &Retrier{
+		backoff: backoff,
+		class:   class,
+		rand:    rand.New(rand.NewSource(time.Now().UnixNano())),
+	}
+}
+
+// Run executes the given work function by executing RunCtx without context.Context.
+func (r *Retrier) Run(work func() error) error {
+	return r.RunCtx(context.Background(), func(ctx context.Context) error {
+		// never use ctx
+		return work()
+	})
+}
+
+// RunCtx executes the given work function, then classifies its return value based on the classifier used
+// to construct the Retrier. If the result is Succeed or Fail, the return value of the work function is
+// returned to the caller. If the result is Retry, then Run sleeps according to the its backoff policy
+// before retrying. If the total number of retries is exceeded then the return value of the work function
+// is returned to the caller regardless.
+func (r *Retrier) RunCtx(ctx context.Context, work func(ctx context.Context) error) error {
+	retries := 0
+	for {
+		ret := work(ctx)
+
+		switch r.class.Classify(ret) {
+		case Succeed, Fail:
+			return ret
+		case Retry:
+			if retries >= len(r.backoff) {
+				return ret
+			}
+
+			timeout := time.After(r.calcSleep(retries))
+			if err := r.sleep(ctx, timeout); err != nil {
+				return err
+			}
+
+			retries++
+		}
+	}
+}
+
+func (r *Retrier) sleep(ctx context.Context, t <-chan time.Time) error {
+	select {
+	case <-t:
+		return nil
+	case <-ctx.Done():
+		return ctx.Err()
+	}
+}
+
+func (r *Retrier) calcSleep(i int) time.Duration {
+	// lock unsafe rand prng
+	r.randMu.Lock()
+	defer r.randMu.Unlock()
+	// take a random float in the range (-r.jitter, +r.jitter) and multiply it by the base amount
+	return r.backoff[i] + time.Duration(((r.rand.Float64()*2)-1)*r.jitter*float64(r.backoff[i]))
+}
+
+// SetJitter sets the amount of jitter on each back-off to a factor between 0.0 and 1.0 (values outside this range
+// are silently ignored). When a retry occurs, the back-off is adjusted by a random amount up to this value.
+func (r *Retrier) SetJitter(jit float64) {
+	if jit < 0 || jit > 1 {
+		return
+	}
+	r.jitter = jit
+}

gomore/retrier/retrier_test.go

@@ -0,0 +1,179 @@
+package retrier
+
+import (
+	"context"
+	"errors"
+	"testing"
+	"time"
+)
+
+var i int
+
+func genWork(returns []error) func() error {
+	i = 0
+	return func() error {
+		i++
+		if i > len(returns) {
+			return nil
+		}
+		return returns[i-1]
+	}
+}
+
+func genWorkWithCtx() func(ctx context.Context) error {
+	i = 0
+	return func(ctx context.Context) error {
+		select {
+		case <-ctx.Done():
+			return errFoo
+		default:
+			i++
+		}
+		return nil
+	}
+}
+
+func TestRetrier(t *testing.T) {
+	r := New([]time.Duration{0, 10 * time.Millisecond}, WhitelistClassifier{errFoo})
+
+	err := r.Run(genWork([]error{errFoo, errFoo}))
+	if err != nil {
+		t.Error(err)
+	}
+	if i != 3 {
+		t.Error("run wrong number of times")
+	}
+
+	err = r.Run(genWork([]error{errFoo, errBar}))
+	if err != errBar {
+		t.Error(err)
+	}
+	if i != 2 {
+		t.Error("run wrong number of times")
+	}
+
+	err = r.Run(genWork([]error{errBar, errBaz}))
+	if err != errBar {
+		t.Error(err)
+	}
+	if i != 1 {
+		t.Error("run wrong number of times")
+	}
+}
+
+func TestRetrierCtx(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+
+	r := New([]time.Duration{0, 10 * time.Millisecond}, WhitelistClassifier{})
+
+	err := r.RunCtx(ctx, genWorkWithCtx())
+	if err != nil {
+		t.Error(err)
+	}
+	if i != 1 {
+		t.Error("run wrong number of times")
+	}
+
+	cancel()
+
+	err = r.RunCtx(ctx, genWorkWithCtx())
+	if err != errFoo {
+		t.Error("context must be cancelled")
+	}
+	if i != 0 {
+		t.Error("run wrong number of times")
+	}
+}
+
+func TestRetrierNone(t *testing.T) {
+	r := New(nil, nil)
+
+	i = 0
+	err := r.Run(func() error {
+		i++
+		return errFoo
+	})
+	if err != errFoo {
+		t.Error(err)
+	}
+	if i != 1 {
+		t.Error("run wrong number of times")
+	}
+
+	i = 0
+	err = r.Run(func() error {
+		i++
+		return nil
+	})
+	if err != nil {
+		t.Error(err)
+	}
+	if i != 1 {
+		t.Error("run wrong number of times")
+	}
+}
+
+func TestRetrierJitter(t *testing.T) {
+	r := New([]time.Duration{0, 10 * time.Millisecond, 4 * time.Hour}, nil)
+
+	if r.calcSleep(0) != 0 {
+		t.Error("Incorrect sleep calculated")
+	}
+	if r.calcSleep(1) != 10*time.Millisecond {
+		t.Error("Incorrect sleep calculated")
+	}
+	if r.calcSleep(2) != 4*time.Hour {
+		t.Error("Incorrect sleep calculated")
+	}
+
+	r.SetJitter(0.25)
+	for i := 0; i < 20; i++ {
+		if r.calcSleep(0) != 0 {
+			t.Error("Incorrect sleep calculated")
+		}
+
+		slp := r.calcSleep(1)
+		if slp < 7500*time.Microsecond || slp > 12500*time.Microsecond {
+			t.Error("Incorrect sleep calculated")
+		}
+
+		slp = r.calcSleep(2)
+		if slp < 3*time.Hour || slp > 5*time.Hour {
+			t.Error("Incorrect sleep calculated")
+		}
+	}
+
+	r.SetJitter(-1)
+	if r.jitter != 0.25 {
+		t.Error("Invalid jitter value accepted")
+	}
+
+	r.SetJitter(2)
+	if r.jitter != 0.25 {
+		t.Error("Invalid jitter value accepted")
+	}
+}
+
+func TestRetrierThreadSafety(t *testing.T) {
+	r := New([]time.Duration{0}, nil)
+	for i := 0; i < 2; i++ {
+		go func() {
+			r.Run(func() error {
+				return errors.New("error")
+			})
+		}()
+	}
+}
+
+func ExampleRetrier() {
+	r := New(ConstantBackoff(3, 100*time.Millisecond), nil)
+
+	err := r.Run(func() error {
+		// do some work
+		return nil
+	})
+
+	if err != nil {
+		// handle the case where the work failed three times
+	}
+}