02-Feb-2022 07:21:19.582 SEVERE [http-nio-8080-exec-1] org.kie.server.controller.websocket.WebSocketKieServerControllerImpl.onKieServerError Unexpected error
        java.util.ConcurrentModificationException
                at java.base/java.util.ArrayList$Itr.checkForComodification(ArrayList.java:1043)
                at java.base/java.util.ArrayList$Itr.next(ArrayList.java:997)
                at com.thoughtworks.xstream.converters.collections.CollectionConverter.marshal(CollectionConverter.java:73)
                at com.thoughtworks.xstream.core.AbstractReferenceMarshaller.convert(AbstractReferenceMarshaller.java:68)
                at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:58)
                at com.thoughtworks.xstream.core.AbstractReferenceMarshaller$1.convertAnother(AbstractReferenceMarshaller.java:83)
                at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.marshallField(AbstractReflectionConverter.java:270)
                at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter$2.writeField(AbstractReflectionConverter.java:174)
                at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.doMarshal(AbstractReflectionConverter.java:262)
                at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.marshal(AbstractReflectionConverter.java:90)
                at com.thoughtworks.xstream.core.AbstractReferenceMarshaller.convert(AbstractReferenceMarshaller.java:68)
                at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:58)
                at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:43)
                at com.thoughtworks.xstream.core.AbstractReferenceMarshaller$1.convertAnother(AbstractReferenceMarshaller.java:87)
                at com.thoughtworks.xstream.converters.collections.AbstractCollectionConverter.writeBareItem(AbstractCollectionConverter.java:94)
                at com.thoughtworks.xstream.converters.collections.AbstractCollectionConverter.writeItem(AbstractCollectionConverter.java:66)
                at com.thoughtworks.xstream.converters.collections.AbstractCollectionConverter.writeCompleteItem(AbstractCollectionConverter.java:81)
                at com.thoughtworks.xstream.converters.collections.CollectionConverter.marshal(CollectionConverter.java:74)
                at com.thoughtworks.xstream.core.AbstractReferenceMarshaller.convert(AbstractReferenceMarshaller.java:68)
                at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:58)
                at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:43)
                at com.thoughtworks.xstream.core.TreeMarshaller.start(TreeMarshaller.java:82)
                at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.marshal(AbstractTreeMarshallingStrategy.java:37)
                at com.thoughtworks.xstream.XStream.marshal(XStream.java:1278)
                at com.thoughtworks.xstream.XStream.marshal(XStream.java:1267)
                at com.thoughtworks.xstream.XStream.toXML(XStream.java:1240)
                at com.thoughtworks.xstream.XStream.toXML(XStream.java:1227)
                at org.kie.server.controller.impl.storage.FileBasedKieServerTemplateStorage.writeTemplateMap(FileBasedKieServerTemplateStorage.java:114)
                at org.kie.server.controller.impl.storage.FileBasedKieServerTemplateStorage.update(FileBasedKieServerTemplateStorage.java:205)
                at org.kie.server.controller.impl.KieServerControllerImpl.connect(KieServerControllerImpl.java:103)
                at org.kie.server.controller.websocket.ConnectedKieServerHandler.onMessage(ConnectedKieServerHandler.java:58)
                at org.kie.server.controller.websocket.common.handlers.KieServerMessageHandler.onMessage(KieServerMessageHandler.java:48)
                at org.kie.server.controller.websocket.common.handlers.KieServerMessageHandler.onMessage(KieServerMessageHandler.java:27)
                at org.apache.tomcat.websocket.WsFrameBase.sendMessageText(WsFrameBase.java:414)
                at org.apache.tomcat.websocket.server.WsFrameServer.sendMessageText(WsFrameServer.java:129)
                at org.apache.tomcat.websocket.WsFrameBase.processDataText(WsFrameBase.java:515)
                at org.apache.tomcat.websocket.WsFrameBase.processData(WsFrameBase.java:301)
                at org.apache.tomcat.websocket.WsFrameBase.processInputBuffer(WsFrameBase.java:133)
                at org.apache.tomcat.websocket.server.WsFrameServer.onDataAvailable(WsFrameServer.java:85)
                at org.apache.tomcat.websocket.server.WsFrameServer.doOnDataAvailable(WsFrameServer.java:183)
                at org.apache.tomcat.websocket.server.WsFrameServer.notifyDataAvailable(WsFrameServer.java:162)
                at org.apache.tomcat.websocket.server.WsHttpUpgradeHandler.upgradeDispatch(WsHttpUpgradeHandler.java:157)
                at org.apache.coyote.http11.upgrade.UpgradeProcessorInternal.dispatch(UpgradeProcessorInternal.java:60)
                at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:59)
                at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:831)
                at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1673)
                at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
                at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
                at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
                at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
                at java.base/java.lang.Thread.run(Thread.java:829)
02-Feb-2022 07:21:19.584 SEVERE [http-nio-8080-exec-1] org.apache.tomcat.websocket.pojo.PojoEndpointBase.onClose Failed to call onClose method of POJO end point for POJO of type [org.kie.server.controller.websocket.WebSocketKieServerControllerImpl]
        java.lang.reflect.InvocationTargetException
                at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
                at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
                at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
                at java.base/java.lang.reflect.Method.invoke(Method.java:566)
                at org.apache.tomcat.websocket.pojo.PojoEndpointBase.onClose(PojoEndpointBase.java:107)
                at org.apache.tomcat.websocket.WsSession.fireEndpointOnClose(WsSession.java:759)
                at org.apache.tomcat.websocket.WsSession.onClose(WsSession.java:740)
                at org.apache.tomcat.websocket.server.WsHttpUpgradeHandler.close(WsHttpUpgradeHandler.java:250)
                at org.apache.tomcat.websocket.server.WsHttpUpgradeHandler.upgradeDispatch(WsHttpUpgradeHandler.java:159)
                at org.apache.coyote.http11.upgrade.UpgradeProcessorInternal.dispatch(UpgradeProcessorInternal.java:60)
                at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:59)
                at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:831)
                at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1673)
                at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
                at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
                at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
                at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
                at java.base/java.lang.Thread.run(Thread.java:829)
        Caused by: java.lang.NullPointerException
                at org.kie.server.controller.websocket.WebSocketSessionManager.removeSession(WebSocketSessionManager.java:74)
                at org.kie.server.controller.websocket.WebSocketKieServerControllerImpl.onKieServerDisconnect(WebSocketKieServerControllerImpl.java:104)
                ... 18 more
02-Feb-2022 07:21:19.584 SEVERE [http-nio-8080-exec-1] org.kie.server.controller.websocket.WebSocketKieServerControllerImpl.onKieServerError Unexpected error
        java.lang.reflect.InvocationTargetException
                at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
                at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
                at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
                at java.base/java.lang.reflect.Method.invoke(Method.java:566)
                at org.apache.tomcat.websocket.pojo.PojoEndpointBase.onClose(PojoEndpointBase.java:107)
                at org.apache.tomcat.websocket.WsSession.fireEndpointOnClose(WsSession.java:759)
                at org.apache.tomcat.websocket.WsSession.onClose(WsSession.java:740)
                at org.apache.tomcat.websocket.server.WsHttpUpgradeHandler.close(WsHttpUpgradeHandler.java:250)
                at org.apache.tomcat.websocket.server.WsHttpUpgradeHandler.upgradeDispatch(WsHttpUpgradeHandler.java:159)
                at org.apache.coyote.http11.upgrade.UpgradeProcessorInternal.dispatch(UpgradeProcessorInternal.java:60)
                at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:59)
                at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:831)
                at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1673)
                at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
                at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
                at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
                at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
                at java.base/java.lang.Thread.run(Thread.java:829)
        Caused by: java.lang.NullPointerException
                at org.kie.server.controller.websocket.WebSocketSessionManager.removeSession(WebSocketSessionManager.java:74)
                at org.kie.server.controller.websocket.WebSocketKieServerControllerImpl.onKieServerDisconnect(WebSocketKieServerControllerImpl.java:104)
                ... 18 more