Elasticsearch Client只初始化一次，但是项目运行到一定时间回报tomcat内存溢出

代码段：
public static Client init() {

        try {
            Properties properties = CommonUtil.readConfig("elasticsearch.properties");
            String clusterName = properties.getProperty("clusterName").trim(); // 集群名称
            String url = properties.getProperty("hosts").trim(); // 访问地址
            String[] location = url.split(",");
            Settings settings = Settings.builder().put("cluster.name", clusterName).build();
            client = new PreBuiltTransportClient(settings)
                    .addTransportAddress(new InetSocketTransportAddress(InetAddress.getByName(location[0]), 9300))
                    .addTransportAddress(new InetSocketTransportAddress(InetAddress.getByName(location[1]),9300));
            
            properties = CommonUtil.readConfig("sort/sort.properties");
            distanceWords = properties.getProperty("distance").trim();
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }
        return client;
    }


    public ElasticUtil() {
        try {
            client = init();
        } catch (Exception e) {
            e.printStackTrace();
        }
        adminClient = client.admin().indices();
    }

异常日志：
10-Aug-2017 17:41:36.840 警告 [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [ROOT] appears to have started a thread named [elasticsearch[_client_][generic][T#4]] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
 sun.misc.Unsafe.park(Native Method)
 java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
 java.util.concurrent.LinkedTransferQueue.awaitMatch(LinkedTransferQueue.java:737)
 java.util.concurrent.LinkedTransferQueue.xfer(LinkedTransferQueue.java:647)
 java.util.concurrent.LinkedTransferQueue.take(LinkedTransferQueue.java:1269)
 java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067)
 java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127)
 java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
 java.lang.Thread.run(Thread.java:748)
10-Aug-2017 17:41:36.841 严重 [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.checkThreadLocalMapForLeaks The web application [ROOT] created a ThreadLocal with key of type [java.lang.ThreadLocal] (value [java.lang.ThreadLocal@740a4cbe]) and a value of type [io.netty.util.internal.InternalThreadLocalMap] (value [io.netty.util.internal.InternalThreadLocalMap@550d63d3]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.