c8d/push: Add distribution source labels only on success

Previously the labels would be appended for content that was pushed
even if subsequent pushes of other content failed.
Change the behavior to only append the labels if the whole push
operation succeeded.

Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>

daemon/containerd/image_push.go

@@ -108,15 +108,8 @@ func (i *ImageService) PushImage(ctx context.Context, targetRef reference.Named,
 		},
 	)
 
-	appendSource, err := docker.AppendDistributionSourceLabel(realStore, targetRef.String())
-	if err != nil {
-		// This shouldn't happen at this point because the reference would have to be invalid
-		// and if it was, then it would error out earlier.
-		return errdefs.Unknown(errors.Wrap(err, "failed to create an handler that appends distribution source label to pushed content"))
-	}
-
 	handlerWrapper := func(h images.Handler) images.Handler {
-		return containerdimages.Handlers(addChildrenToJobs, h, appendSource)
+		return containerdimages.Handlers(addChildrenToJobs, h)
 	}
 
 	err = remotes.PushContent(ctx, pusher, target, store, limiter, platforms.All, handlerWrapper)
@@ -132,7 +125,21 @@ func (i *ImageService) PushImage(ctx context.Context, targetRef reference.Named,
 					err))
 			}
 		}
+	} else {
+		appendSource, err := docker.AppendDistributionSourceLabel(realStore, targetRef.String())
+		if err != nil {
+			// This shouldn't happen at this point because the reference would have to be invalid
+			// and if it was, then it would error out earlier.
+			return errdefs.Unknown(errors.Wrap(err, "failed to create an handler that appends distribution source label to pushed content"))
+		}
+
+		if err := containerdimages.Dispatch(ctx, appendSource, nil, target); err != nil {
+			// Shouldn't happen, but even if it would fail, then make it only a warning
+			// because it doesn't affect the pushed data.
+			logrus.WithError(err).Warn("failed to append distribution source labels to pushed content")
+		}
 	}
+
 	return err
 }