if (executorService == null) {
                int numThreads = ComponentUtil.getFessConfig().getRankFusionThreadsAsInteger();
                if (numThreads <= 0) {
                    numThreads = (Runtime.getRuntime().availableProcessors() * 3) / 2 + 1;
                }
                executorService = Executors.newFixedThreadPool(numThreads);
            }
        }
    }