probeDirectory.mkdirs();
                startWatchingProbeDirectory(probeDirectory);
                probeRegistry.armWatchProbe(probedHierarchy);
            });
    }

    protected abstract void updateWatchesOnChangedWatchedFiles(FileHierarchySet newWatchedFiles);

    protected abstract void startWatchingProbeDirectory(File probeDirectory);

        }

        LOGGER.debug("Watching {} directory hierarchies to track changes", watchedHierarchies.size());
    }

    @Override
    protected void startWatchingProbeDirectory(File probeDirectory) {
        // We already started watching the hierarchy.
    }

    @Override
    protected void stopWatchingProbeDirectory(File probeDirectory) {

            return invalidatedRoot;
        };
    }

    @Override
    protected void startWatchingProbeDirectory(File probeDirectory) {
        updateWatchedDirectories(ImmutableMap.of(probeDirectory.getAbsolutePath(), 1));
    }

    @Override
    protected void stopWatchingProbeDirectory(File probeDirectory) {