java.nio.channels.ClosedChannelException
	at jenkins.agents.WebSocketAgents$Session.closed(WebSocketAgents.java:153)
	at jenkins.websocket.WebSockets$1.onWebSocketClose(WebSockets.java:80)
	at jenkins.websocket.Jetty10Provider$2.onWebSocketClose(Jetty10Provider.java:149)
	at org.eclipse.jetty.websocket.common.JettyWebSocketFrameHandler.notifyOnClose(JettyWebSocketFrameHandler.java:308)
	at org.eclipse.jetty.websocket.common.JettyWebSocketFrameHandler.onClosed(JettyWebSocketFrameHandler.java:292)
	at org.eclipse.jetty.websocket.core.internal.WebSocketCoreSession.lambda$closeConnection$0(WebSocketCoreSession.java:272)
	at org.eclipse.jetty.server.handler.ContextHandler.handle(ContextHandler.java:1450)
	at org.eclipse.jetty.server.handler.ContextHandler.handle(ContextHandler.java:1487)
	at org.eclipse.jetty.websocket.core.server.internal.AbstractHandshaker$1.handle(AbstractHandshaker.java:212)
	at org.eclipse.jetty.websocket.core.internal.WebSocketCoreSession.lambda$closeConnection$1(WebSocketCoreSession.java:272)
	at org.eclipse.jetty.util.Callback$4.completed(Callback.java:184)
	at org.eclipse.jetty.util.Callback$Completing.succeeded(Callback.java:344)
	at org.eclipse.jetty.websocket.common.JettyWebSocketFrameHandler.onError(JettyWebSocketFrameHandler.java:268)
	at org.eclipse.jetty.websocket.core.internal.WebSocketCoreSession.lambda$closeConnection$2(WebSocketCoreSession.java:284)
	at org.eclipse.jetty.server.handler.ContextHandler.handle(ContextHandler.java:1468)
	at org.eclipse.jetty.server.handler.ContextHandler.handle(ContextHandler.java:1487)
	at org.eclipse.jetty.websocket.core.server.internal.AbstractHandshaker$1.handle(AbstractHandshaker.java:212)
	at org.eclipse.jetty.websocket.core.internal.WebSocketCoreSession.closeConnection(WebSocketCoreSession.java:284)
	at org.eclipse.jetty.websocket.core.internal.WebSocketCoreSession.lambda$sendFrame$8(WebSocketCoreSession.java:520)
	at org.eclipse.jetty.util.Callback$3.failed(Callback.java:161)
	at org.eclipse.jetty.websocket.core.internal.TransformingFlusher.notifyCallbackFailure(TransformingFlusher.java:213)
	at org.eclipse.jetty.websocket.core.internal.TransformingFlusher.onFailure(TransformingFlusher.java:126)
	at org.eclipse.jetty.websocket.core.internal.TransformingFlusher$Flusher.onCompleteFailure(TransformingFlusher.java:185)
	at org.eclipse.jetty.util.IteratingCallback.failed(IteratingCallback.java:386)
	at org.eclipse.jetty.websocket.core.internal.FrameFlusher.notifyCallbackFailure(FrameFlusher.java:469)
	at org.eclipse.jetty.websocket.core.internal.FrameFlusher.onCompleteFailure(FrameFlusher.java:431)
	at org.eclipse.jetty.websocket.core.internal.WebSocketConnection$Flusher.onCompleteFailure(WebSocketConnection.java:655)
	at org.eclipse.jetty.util.IteratingCallback.failed(IteratingCallback.java:386)
	at org.eclipse.jetty.util.Callback$Nested.failed(Callback.java:405)
	at org.eclipse.jetty.io.WriteFlusher.fail(WriteFlusher.java:346)
	at org.eclipse.jetty.io.WriteFlusher.write(WriteFlusher.java:293)
	at org.eclipse.jetty.io.WriteFlusher.write(WriteFlusher.java:254)
	at org.eclipse.jetty.io.AbstractEndPoint.write(AbstractEndPoint.java:386)
	at org.eclipse.jetty.websocket.core.internal.FrameFlusher.process(FrameFlusher.java:330)
	at org.eclipse.jetty.util.IteratingCallback.processing(IteratingCallback.java:232)
	at org.eclipse.jetty.util.IteratingCallback.iterate(IteratingCallback.java:214)
	at org.eclipse.jetty.websocket.core.internal.WebSocketConnection.enqueueFrame(WebSocketConnection.java:640)
	at org.eclipse.jetty.websocket.core.internal.WebSocketCoreSession$OutgoingAdaptor.sendFrame(WebSocketCoreSession.java:724)
	at org.eclipse.jetty.websocket.core.internal.ExtensionStack.sendFrame(ExtensionStack.java:258)
	at org.eclipse.jetty.websocket.core.internal.WebSocketCoreSession$Flusher.forwardFrame(WebSocketCoreSession.java:815)
	at org.eclipse.jetty.websocket.core.internal.FragmentingFlusher.onFrame(FragmentingFlusher.java:50)
	at org.eclipse.jetty.websocket.core.internal.TransformingFlusher$Flusher.process(TransformingFlusher.java:163)
	at org.eclipse.jetty.util.IteratingCallback.processing(IteratingCallback.java:232)
	at org.eclipse.jetty.util.IteratingCallback.iterate(IteratingCallback.java:214)
	at org.eclipse.jetty.websocket.core.internal.TransformingFlusher.sendFrame(TransformingFlusher.java:77)
	at org.eclipse.jetty.websocket.core.internal.WebSocketCoreSession.sendFrame(WebSocketCoreSession.java:526)
	at org.eclipse.jetty.websocket.common.JettyWebSocketRemoteEndpoint.sendPing(JettyWebSocketRemoteEndpoint.java:143)
	at jenkins.websocket.Jetty10Provider$1.sendPing(Jetty10Provider.java:94)
	at jenkins.websocket.WebSocketSession.lambda$startPings$0(WebSocketSession.java:71)
	at jenkins.security.ImpersonatingScheduledExecutorService$1.run(ImpersonatingScheduledExecutorService.java:69)
	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
	at java.base/java.util.concurrent.FutureTask.runAndReset(FutureTask.java:305)
	at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:305)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
	at java.base/java.lang.Thread.run(Thread.java:829)
Caused: java.io.IOException: Backing channel 'automachine4' is disconnected.