Elasticsearch warning logs while stopping tomcat

Hi

Im using ELK 7.10.2 and uses below code to connect to Elasticsearch using java

Settings settings = Settings.builder()
					.put("cluster.name", elkUtil.getClusterName(Constants.ELASTICSEARCH_YAML_PATH)).build();
			 esClient = new PreBuiltTransportClient(settings)
			        .addTransportAddress(new TransportAddress(InetAddress.getByName(host), 9300));

While stopping spring boot, Im calling Client.close as below

public synchronized void shutdownES(){
		esClient.close();
		logger.info("Remote connection closed to ES");
	}

But still Tomcat logs throw below warning

an 31, 2022 6:39:46 PM org.apache.catalina.loader.WebappClassLoaderBase clearReferencesThreads
WARNING: The web application [ROOT] appears to have started a thread named [elasticsearch[_client_][generic][T#2]] 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:1074)
 java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
 java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
 java.lang.Thread.run(Thread.java:748)
Jan 31, 2022 6:39:46 PM org.apache.catalina.loader.WebappClassLoaderBase clearReferencesThreads
WARNING: The web application [ROOT] appears to have started a thread named [elasticsearch[_client_][transport_worker][T#2]] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
 sun.nio.ch.EPollArrayWrapper.epollWait(Native Method)
 sun.nio.ch.EPollArrayWrapper.poll(EPollArrayWrapper.java:269)
 sun.nio.ch.EPollSelectorImpl.doSelect(EPollSelectorImpl.java:93)
 sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86)
 sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97)
 sun.nio.ch.SelectorImpl.select(SelectorImpl.java:101)
 io.netty.channel.nio.NioEventLoop.select(NioEventLoop.java:803)
 io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:457)
 io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989)
 io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
 java.lang.Thread.run(Thread.java:748)
Jan 31, 2022 6:39:46 PM org.apache.catalina.loader.WebappClassLoaderBase clearReferencesThreads
WARNING: The web application [ROOT] appears to have started a thread named [elasticsearch[_client_][generic][T#3]] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
 sun.misc.Unsafe.park(Native Method)
 java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
 java.util.concurrent.LinkedTransferQueue.awaitMatch(LinkedTransferQueue.java:737)
 java.util.concurrent.LinkedTransferQueue.xfer(LinkedTransferQueue.java:647)
 java.util.concurrent.LinkedTransferQueue.take(LinkedTransferQueue.java:1269)
 java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)
 java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)
 java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
 java.lang.Thread.run(Thread.java:748)

What am I doing wrong here? Can someone please help

Don't use the TransportClient. It has been deprecated.
Please also upgrade your cluster to 7.16.