Add success callback to the backend

cmd/restic/global.go

@@ -439,9 +439,13 @@ func OpenRepository(opts GlobalOptions) (*repository.Repository, error) {
 		return nil, err
 	}
 
-	be = backend.NewRetryBackend(be, 10, func(msg string, err error, d time.Duration) {
+	report := func(msg string, err error, d time.Duration) {
 		Warnf("%v returned error, retrying after %v: %v\n", msg, d, err)
-	})
+	}
+	success := func(msg string, retries int) {
+		Warnf("%v operation successful after %d retries\n", msg, retries)
+	}
+	be = backend.NewRetryBackend(be, 10, report, success)
 
 	// wrap backend if a test specified a hook
 	if opts.backendTestHook != nil {

internal/backend/backend_retry.go

@@ -17,6 +17,7 @@ type RetryBackend struct {
 	restic.Backend
 	MaxTries int
 	Report   func(string, error, time.Duration)
+	Success  func(string, int)
 }
 
 // statically ensure that RetryBackend implements restic.Backend.
@@ -24,27 +25,30 @@ var _ restic.Backend = &RetryBackend{}
 
 // NewRetryBackend wraps be with a backend that retries operations after a
 // backoff. report is called with a description and the error, if one occurred.
-func NewRetryBackend(be restic.Backend, maxTries int, report func(string, error, time.Duration)) *RetryBackend {
+// success is called with the number of retries before a successful operation
+// (it is not called if it succeeded on the first try)
+func NewRetryBackend(be restic.Backend, maxTries int, report func(string, error, time.Duration), success func(string, int)) *RetryBackend {
 	return &RetryBackend{
 		Backend:  be,
 		MaxTries: maxTries,
 		Report:   report,
+		Success:  success,
 	}
 }
 
-// retryNotifyErrorWithSuccess is an extension of backoff.RetryNotify with notification of success after an error
+// retryNotifyErrorWithSuccess is an extension of backoff.RetryNotify with notification of success after an error.
-// success is NOT notified on the first run of operation (only after an error)
+// success is NOT notified on the first run of operation (only after an error).
-func retryNotifyErrorWithSuccess(operation backoff.Operation, b backoff.BackOff, notify backoff.Notify, success func()) error {
+func retryNotifyErrorWithSuccess(operation backoff.Operation, b backoff.BackOff, notify backoff.Notify, success func(retries int)) error {
 	if success == nil {
 		return backoff.RetryNotify(operation, b, notify)
 	}
-	errorDetected := false
+	retries := 0
 	operationWrapper := func() error {
 		err := operation()
 		if err != nil {
-			errorDetected = true
+			retries++
-		} else if errorDetected {
+		} else if retries > 0 {
-			success()
+			success(retries)
 		}
 		return err
 	}
@@ -62,13 +66,18 @@ func (be *RetryBackend) retry(ctx context.Context, msg string, f func() error) e
 		return ctx.Err()
 	}
 
-	err := backoff.RetryNotify(f,
+	err := retryNotifyErrorWithSuccess(f,
 		backoff.WithContext(backoff.WithMaxRetries(backoff.NewExponentialBackOff(), uint64(be.MaxTries)), ctx),
 		func(err error, d time.Duration) {
 			if be.Report != nil {
 				be.Report(msg, err, d)
 			}
 		},
+		func(retries int) {
+			if be.Success != nil {
+				be.Success(msg, retries)
+			}
+		},
 	)
 
 	return err

internal/backend/backend_retry_test.go

@@ -35,7 +35,7 @@ func TestBackendSaveRetry(t *testing.T) {
 		},
 	}
 
-	retryBackend := NewRetryBackend(be, 10, nil)
+	retryBackend := NewRetryBackend(be, 10, nil, nil)
 
 	data := test.Random(23, 5*1024*1024+11241)
 	err := retryBackend.Save(context.TODO(), restic.Handle{}, restic.NewByteReader(data, be.Hasher()))
@@ -70,7 +70,7 @@ func TestBackendSaveRetryAtomic(t *testing.T) {
 		HasAtomicReplaceFn: func() bool { return true },
 	}
 
-	retryBackend := NewRetryBackend(be, 10, nil)
+	retryBackend := NewRetryBackend(be, 10, nil, nil)
 
 	data := test.Random(23, 5*1024*1024+11241)
 	err := retryBackend.Save(context.TODO(), restic.Handle{}, restic.NewByteReader(data, be.Hasher()))
@@ -103,7 +103,7 @@ func TestBackendListRetry(t *testing.T) {
 		},
 	}
 
-	retryBackend := NewRetryBackend(be, 10, nil)
+	retryBackend := NewRetryBackend(be, 10, nil, nil)
 
 	var listed []string
 	err := retryBackend.List(context.TODO(), restic.PackFile, func(fi restic.FileInfo) error {
@@ -132,7 +132,7 @@ func TestBackendListRetryErrorFn(t *testing.T) {
 		},
 	}
 
-	retryBackend := NewRetryBackend(be, 10, nil)
+	retryBackend := NewRetryBackend(be, 10, nil, nil)
 
 	var ErrTest = errors.New("test error")
 
@@ -188,7 +188,7 @@ func TestBackendListRetryErrorBackend(t *testing.T) {
 	}
 
 	const maxRetries = 2
-	retryBackend := NewRetryBackend(be, maxRetries, nil)
+	retryBackend := NewRetryBackend(be, maxRetries, nil, nil)
 
 	var listed []string
 	err := retryBackend.List(context.TODO(), restic.PackFile, func(fi restic.FileInfo) error {
@@ -257,7 +257,7 @@ func TestBackendLoadRetry(t *testing.T) {
 		return failingReader{data: data, limit: limit}, nil
 	}
 
-	retryBackend := NewRetryBackend(be, 10, nil)
+	retryBackend := NewRetryBackend(be, 10, nil, nil)
 
 	var buf []byte
 	err := retryBackend.Load(context.TODO(), restic.Handle{}, 0, 0, func(rd io.Reader) (err error) {
@@ -276,7 +276,7 @@ func assertIsCanceled(t *testing.T, err error) {
 func TestBackendCanceledContext(t *testing.T) {
 	// unimplemented mock backend functions return an error by default
 	// check that we received the expected context canceled error instead
-	retryBackend := NewRetryBackend(mock.NewBackend(), 2, nil)
+	retryBackend := NewRetryBackend(mock.NewBackend(), 2, nil, nil)
 	h := restic.Handle{Type: restic.PackFile, Name: restic.NewRandomID().String()}
 
 	// create an already canceled context
@@ -313,7 +313,7 @@ func TestNotifyWithSuccessIsNotCalled(t *testing.T) {
 		t.Fatal("Notify should not have been called")
 	}
 
-	success := func() {
+	success := func(retries int) {
 		t.Fatal("Success should not have been called")
 	}
 
@@ -339,7 +339,7 @@ func TestNotifyWithSuccessIsCalled(t *testing.T) {
 	}
 
 	successCalled := 0
-	success := func() {
+	success := func(retries int) {
 		successCalled++
 	}