Merge pull request #1623 from restic/backend-relax-restrictions

backend: Relax requirement for new files

changelog/0.8.3/pull-1623

@@ -0,0 +1,12 @@
+Enhancement: Don't check for presence of files in the backend before writing
+
+Before, all backend implementations were required to return an error if the
+file that is to be written already exists in the backend. For most backends,
+that means making a request (e.g. via HTTP) and returning an error when the
+file already exists.
+
+This is not accurate, the file could have been created between the HTTP request
+testing for it, and when writing starts, so we've relaxed this requeriment,
+which saves one additional HTTP request per newly added file.
+
+https://github.com/restic/restic/pull/1623

internal/backend/azure/azure.go

@@ -135,16 +135,6 @@ func (be *Backend) Save(ctx context.Context, h restic.Handle, rd io.Reader) (err
 
 	debug.Log("Save %v at %v", h, objName)
 
-	// Check key does not already exist
-	found, err := be.container.GetBlobReference(objName).Exists()
-	if err != nil {
-		return errors.Wrap(err, "GetBlobReference().Exists()")
-	}
-	if found {
-		debug.Log("%v already exists", h)
-		return errors.New("key already exists")
-	}
-
 	be.sem.GetToken()
 
 	// wrap the reader so that net/http client cannot close the reader, return

internal/backend/b2/b2.go

@@ -200,12 +200,6 @@ func (be *b2Backend) Save(ctx context.Context, h restic.Handle, rd io.Reader) er
 	debug.Log("Save %v, name %v", h, name)
 	obj := be.bucket.Object(name)
 
-	_, err := obj.Attrs(ctx)
-	if err == nil {
-		debug.Log("  %v already exists", h)
-		return errors.New("key already exists")
-	}
-
 	w := obj.NewWriter(ctx)
 	n, err := io.Copy(w, rd)
 	debug.Log("  saved %d bytes, err %v", n, err)

internal/backend/gs/gs.go

@@ -218,13 +218,6 @@ func (be *Backend) Save(ctx context.Context, h restic.Handle, rd io.Reader) (err
 
 	be.sem.GetToken()
 
-	// Check key does not already exist
-	if _, err := be.service.Objects.Get(be.bucketName, objName).Do(); err == nil {
-		debug.Log("%v already exists", h)
-		be.sem.ReleaseToken()
-		return errors.New("key already exists")
-	}
-
 	debug.Log("InsertObject(%v, %v)", be.bucketName, objName)
 
 	// Set chunk size to zero to disable resumable uploads.

internal/backend/s3/s3.go

@@ -235,13 +235,6 @@ func (be *Backend) Save(ctx context.Context, h restic.Handle, rd io.Reader) (err
 	be.sem.GetToken()
 	defer be.sem.ReleaseToken()
 
-	// Check key does not already exist
-	_, err = be.client.StatObject(be.cfg.Bucket, objName, minio.StatObjectOptions{})
-	if err == nil {
-		debug.Log("%v already exists", h)
-		return errors.New("key already exists")
-	}
-
 	var size int64 = -1
 
 	type lenner interface {

internal/backend/swift/swift.go

@@ -168,19 +168,6 @@ func (be *beSwift) Save(ctx context.Context, h restic.Handle, rd io.Reader) (err
 	be.sem.GetToken()
 	defer be.sem.ReleaseToken()
 
-	// Check key does not already exist
-	switch _, _, err = be.conn.Object(be.container, objName); err {
-	case nil:
-		debug.Log("%v already exists", h)
-		return errors.New("key already exists")
-
-	case swift.ObjectNotFound:
-		// Ok, that's what we want
-
-	default:
-		return errors.Wrap(err, "conn.Object")
-	}
-
 	encoding := "binary/octet-stream"
 
 	debug.Log("PutObject(%v, %v, %v)", be.container, objName, encoding)

internal/backend/test/tests.go

@@ -764,14 +764,10 @@ func (s *Suite) TestBackend(t *testing.T) {
 
 		// test adding the first file again
 		ts := testStrings[0]
-
-		// create blob
 		h := restic.Handle{Type: tpe, Name: ts.id}
-		err := b.Save(context.TODO(), h, strings.NewReader(ts.data))
-		test.Assert(t, err != nil, "backend has allowed overwrite of existing blob: expected error for %v, got %v", h, err)
 
 		// remove and recreate
-		err = s.delayedRemove(t, b, h)
+		err := s.delayedRemove(t, b, h)
 		test.OK(t, err)
 
 		// test that the blob is gone