/**
     * Adds a listener that is notified when a lock is released. Called while the state lock is held.
     */
    void addLockReleaseListener(Action<ResourceLock> listener);

    void removeLockReleaseListener(Action<ResourceLock> listener);

    public void addLockReleaseListener(Action<ResourceLock> listener) {
        synchronized (lock) {
            releaseHandlers.add(listener);
        }
    }

    @Override
    public void removeLockReleaseListener(Action<ResourceLock> listener) {
        synchronized (lock) {
            releaseHandlers.remove(listener);
        }
    }

    @Override
    public void withStateLock(final Runnable action) {

        return contents;
    }

    @Override
    public WorkSource<Node> asWorkSource() {
        return this;
    }

    @Override
    public void close() {
        lockCoordinator.removeLockReleaseListener(resourceUnlockListener);
        waitingToStartNodes.clear();
        readyNodes.clear();
        runningNodes.clear();
        reachableCache.clear();
    }