@SuppressWarnings( "LockAcquiredButNotSafelyReleased" )
    private void acquireLock(CacheKey key) {
        ReentrantLock lock = lookupLockForAcquire(key);
        lock.lock();
    }
Keep track of the locks that are currently being used.
xmppserver/src/main/java/org/jivesoftware/util/cache/lock/LocalLock.java