introduce MarkTemporary

retry.go

@@ -88,6 +88,9 @@ func (p *Policy) Do(ctx context.Context, f func() error) error {
 	if err := retrier.err; err != nil {
 		return err
 	}
+	if err, ok := err.(*temporaryError); ok {
+		return err.error
+	}
 	return err
 }
 
@@ -118,6 +121,27 @@ func MarkPermanent(err error) error {
 	return &permanentError{err}
 }
 
+type temporaryError struct {
+	error
+}
+
+// implements interface{ Temporary() bool }
+// Inspecting errors https://dave.cheney.net/2014/12/24/inspecting-errors
+func (e *temporaryError) Temporary() bool {
+	return true
+}
+
+// Unwrap implements errors.Wrapper.
+func (e *temporaryError) Unwrap() error {
+	return e.error
+}
+
+// MarkTemporary marks err as a temporary error.
+// It returns the error that implements interface{ Temporary() bool } and Temporary() returns true.
+func MarkTemporary(err error) error {
+	return &temporaryError{err}
+}
+
 // Continue returns whether retrying should be continued.
 func (r *Retrier) Continue() bool {
 	r.count++

retry_test.go

@@ -266,13 +266,34 @@ func TestDo_Success(t *testing.T) {
 
 func TestDo_MarkPermanent(t *testing.T) {
 	permanentErr := errors.New("permanent error")
-	policy := &Policy{}
+	policy := &Policy{MaxCount: 10}
+	count := 0
 	err := policy.Do(context.Background(), func() error {
+		count++
 		return MarkPermanent(permanentErr)
 	})
 	if err != permanentErr {
 		t.Errorf("want error is %#v, got %#v", err, permanentErr)
 	}
+	if count != 1 {
+		t.Errorf("want %d, got %d", 1, count)
+	}
+}
+
+func TestDo_MarkTemporary(t *testing.T) {
+	temporaryErr := errors.New("temporary error")
+	policy := &Policy{MaxCount: 10}
+	count := 0
+	err := policy.Do(context.Background(), func() error {
+		count++
+		return MarkTemporary(temporaryErr)
+	})
+	if err != temporaryErr {
+		t.Errorf("want error is %#v, got %#v", err, temporaryErr)
+	}
+	if count != 10 {
+		t.Errorf("want %d, got %d", 10, count)
+	}
 }
 
 type customError bool