mod_proxy_wstunnel / mod_cluster interoperability issues

Investigation going on....

• Works fine without balancer
• crumbles with httpd in between
• no apparent errors in httpd log

  ERROR [org.apache.catalina.core.ContainerBase.[jboss.web].[default-host].[/clusterbench].[default]] (http-/192.168.122.172:8080-1) JBWEB000236: Servlet.service() for servlet default threw exception: java.lang.IllegalStateException: JBWEB000034: Cannot upgrade from HTTP/1.1 without IO events
  at org.apache.catalina.connector.Response.sendUpgrade(Response.java:1370) [jbossweb-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
  at org.apache.catalina.connector.Request.upgrade(Request.java:3345) [jbossweb-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
  at org.apache.catalina.connector.RequestFacade.upgrade(RequestFacade.java:1062) [jbossweb-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
  at org.apache.tomcat.websocket.server.UpgradeUtil.doUpgrade(UpgradeUtil.java:226) [jbossweb-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
  at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:77) [jbossweb-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:246) [jbossweb-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214) [jbossweb-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
  at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:231) [jbossweb-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
  at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:149) [jbossweb-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
  at org.jboss.modcluster.container.jbossweb.JBossWebContext$RequestListenerValve.event(JBossWebContext.java:91)
  at org.jboss.modcluster.container.jbossweb.JBossWebContext$RequestListenerValve.invoke(JBossWebContext.java:72)
  at org.jboss.as.web.session.ClusteredSessionValve.handleRequest(ClusteredSessionValve.java:134) [jboss-as-web-7.5.4.Final-redhat-4.jar:7.5.4.Final-redhat-4]
  at org.jboss.as.web.session.ClusteredSessionValve.invoke(ClusteredSessionValve.java:99) [jboss-as-web-7.5.4.Final-redhat-4.jar:7.5.4.Final-redhat-4]
  at org.jboss.as.web.session.JvmRouteValve.invoke(JvmRouteValve.java:92) [jboss-as-web-7.5.4.Final-redhat-4.jar:7.5.4.Final-redhat-4]
  at org.jboss.as.web.session.LockingValve.invoke(LockingValve.java:64) [jboss-as-web-7.5.4.Final-redhat-4.jar:7.5.4.Final-redhat-4]
  at org.jboss.as.web.security.SecurityContextAssociationValve.invoke(SecurityContextAssociationValve.java:169) [jboss-as-web-7.5.4.Final-redhat-4.jar:7.5.4.Final-redhat-4]
  at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:150) [jbossweb-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
  at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:97) [jbossweb-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
  at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:102) [jbossweb-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
  at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:344) [jbossweb-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
  at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:854) [jbossweb-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
  at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:653) [jbossweb-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
  at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:926) [jbossweb-7.5.11.Final-redhat-1.jar:7.5.11.Final-redhat-1]
  at java.lang.Thread.run(Thread.java:745) [rt.jar:1.8.0_60]
  
  [New I/O worker #1] WARN com.ning.http.client.providers.netty.handler.WebSocketProtocol - onError {}
  java.lang.AssertionError: [httpd]: Url:[ws://192.168.122.172:8847/clusterbench/websocket] WebSocket error: Invalid Status Code 500
  at org.junit.Assert.fail(Assert.java:88)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  at java.lang.reflect.Method.invoke(Method.java:497)
  at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
  at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:324)
  at org.codehaus.groovy.runtime.callsite.StaticMetaMethodSite$StaticMetaMethodSiteNoUnwrap.invoke(StaticMetaMethodSite.java:130)
  at org.codehaus.groovy.runtime.callsite.StaticMetaMethodSite.callStatic(StaticMetaMethodSite.java:99)
  at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallStatic(CallSiteArray.java:53)
  at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callStatic(AbstractCallSite.java:157)
  at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callStatic(AbstractCallSite.java:165)
  at noe.modcluster.tests.WebSocketsTest$1.onError(WebSocketsTest.groovy:110)
  at com.ning.http.client.ws.WebSocketUpgradeHandler.onCompleted(WebSocketUpgradeHandler.java:78)
  at com.ning.http.client.providers.netty.handler.WebSocketProtocol.handle(WebSocketProtocol.java:100)
  at com.ning.http.client.providers.netty.handler.Processor.messageReceived(Processor.java:88)
  at org.jboss.netty.channel.SimpleChannelUpstreamHandler.handleUpstream(SimpleChannelUpstreamHandler.java:70)
  at org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream(DefaultChannelPipeline.java:564)
  at org.jboss.netty.channel.DefaultChannelPipeline$DefaultChannelHandlerContext.sendUpstream(DefaultChannelPipeline.java:791)
  at org.jboss.netty.channel.Channels.fireMessageReceived(Channels.java:296)
  at org.jboss.netty.handler.codec.frame.FrameDecoder.unfoldAndFireMessageReceived(FrameDecoder.java:459)
  at org.jboss.netty.handler.codec.replay.ReplayingDecoder.callDecode(ReplayingDecoder.java:536)
  at org.jboss.netty.handler.codec.replay.ReplayingDecoder.messageReceived(ReplayingDecoder.java:485)
  at org.jboss.netty.channel.SimpleChannelUpstreamHandler.handleUpstream(SimpleChannelUpstreamHandler.java:70)
  at org.jboss.netty.handler.codec.http.HttpClientCodec.handleUpstream(HttpClientCodec.java:92)
  at org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream(DefaultChannelPipeline.java:564)
  at org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream(DefaultChannelPipeline.java:559)
  at org.jboss.netty.channel.Channels.fireMessageReceived(Channels.java:268)
  at org.jboss.netty.channel.Channels.fireMessageReceived(Channels.java:255)
  at org.jboss.netty.channel.socket.nio.NioWorker.read(NioWorker.java:88)
  at org.jboss.netty.channel.socket.nio.AbstractNioWorker.process(AbstractNioWorker.java:108)
  at org.jboss.netty.channel.socket.nio.AbstractNioSelector.run(AbstractNioSelector.java:337)
  at org.jboss.netty.channel.socket.nio.AbstractNioWorker.run(AbstractNioWorker.java:89)
  at org.jboss.netty.channel.socket.nio.NioWorker.run(NioWorker.java:178)
  at org.jboss.netty.util.ThreadRenamingRunnable.run(ThreadRenamingRunnable.java:108)
  at org.jboss.netty.util.internal.DeadLockProofWorker$1.run(DeadLockProofWorker.java:42)
  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
  at java.lang.Thread.run(Thread.java:745)