DEBUG o.atmosphere.cpr.DefaultBroadcaster Failed to execute a write operation for Broadcaster - Atmosphere/atmosphere Wiki

There is some scenarios where more than one thread start executing a broadcast operation. If the first thread broadcast and the connection is resumed by the browser or the server (closed), a WebServer can throw an exception like:

INFO: 11:46:35.375 [Atmosphere-AsyncWrite-2] DEBUG o.atmosphere.cpr.DefaultBroadcaster - Failed to execute a write operation for Broadcaster 
java.lang.NullPointerException: null
  at org.apache.catalina.connector.Request.setAttribute(Request.java:1689) ~[web-core.jar]
  at org.apache.catalina.connector.RequestFacade.setAttribute(RequestFacade.java:570) ~[web-core.jar]
  at org.atmosphere.cpr.AtmosphereRequest.setAttribute(AtmosphereRequest.java:531) ~[atmosphere-runtime]
  at org.atmosphere.cpr.DefaultBroadcaster.executeAsyncWrite(DefaultBroadcaster.java:731) ~[atmosphere-runtime]
  at org.atmosphere.cpr.DefaultBroadcaster$3.run(DefaultBroadcaster.java:793) ~[atmosphere-runtime]

or

10:02:54.143 [http-nio-8080-exec-6] ERROR o.atmosphere.cpr.AtmosphereFramework - AtmosphereFramework exception
java.lang.IllegalStateException: Request object no longer valid. This object has been cancelled
        at org.atmosphere.cpr.AtmosphereResourceImpl.getRequest(AtmosphereResourceImpl.java:503) ~[atmosphere-runtime-1.0.1.jar:1.0.1]
        at org.atmosphere.cpr.AtmosphereResourceImpl.getRequest(AtmosphereResourceImpl.java:523) ~[atmosphere-runtime-1.0.1.jar:1.0.1]
        at org.atmosphere.gwt.server.impl.GwtAtmosphereResourceImpl.getRequest(GwtAtmosphereResourceImpl.java:151) ~[atmosphere-gwt-server-1.0.1.jar:1.0.1]
        at org.atmosphere.gwt.server.AtmosphereGwtHandler.doServerMessage(AtmosphereGwtHandler.java:279) ~[atmosphere-gwt-server-1.0.1.jar:1.0.1]
        at org.atmosphere.gwt.server.AtmosphereGwtHandler.onRequest(AtmosphereGwtHandler.java:215) ~[atmosphere-gwt-server-1.0.1.jar:1.0.1]
        at org.atmosphere.cpr.AsynchronousProcessor.action(AsynchronousProcessor.java:256) ~[atmosphere-runtime-1.0.1.jar:1.0.1]
        at org.atmosphere.cpr.AsynchronousProcessor.suspended(AsynchronousProcessor.java:166) ~[atmosphere-runtime-1.0.1.jar:1.0.1]
        at org.atmosphere.container.Tomcat7CometSupport.service(Tomcat7CometSupport.java:85) ~[atmosphere-runtime-1.0.1.jar:1.0.1]
        at org.atmosphere.cpr.AtmosphereFramework.doCometSupport(AtmosphereFramework.java:1293) ~[atmosphere-runtime-1.0.1.jar:1.0.1]
        at org.atmosphere.cpr.AtmosphereServlet.event(AtmosphereServlet.java:348) [atmosphere-runtime-1.0.1.jar:1.0.1]
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilterEvent(ApplicationFilterChain.java:484) [catalina.jar:7.0.23]
        at org.apache.catalina.core.ApplicationFilterChain.doFilterEvent(ApplicationFilterChain.java:377) [catalina.jar:7.0.23]
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222) [catalina.jar:7.0.23]
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169) [catalina.jar:7.0.23]
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) [catalina.jar:7.0.23]
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168) [catalina.jar:7.0.23]
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98) [catalina.jar:7.0.23]
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:928) [catalina.jar:7.0.23]
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) [catalina.jar:7.0.23]
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407) [catalina.jar:7.0.23]
        at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:987) [tomcat-coyote.jar:7.0.23]
        at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:539) [tomcat-coyote.jar:7.0.23]
        at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1571) [tomcat-coyote.jar:7.0.23]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) [na:1.7.0_03]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [na:1.7.0_03]
        at java.lang.Thread.run(Unknown Source) [na:1.7.0_03]

This exception is expected and properly handled by Atmosphere. The message may have been lost so it will be cached inside a BroadcasterCache (if one is installed). Most of the time the message will have been delivered successfully.