Good question. MyFaces does not start any thread, as far as I know. On richfaces I don't know.
Maybe it is some tomcat thread who accesses the request map. Or maybe it is even the test environment. Anyway, I'd say as long as this is no production problem, I would ignore it. Regards, Jakob 2010/4/9 Michael Heinen <[email protected]> > Thanks Jakob for the analysis. > > But what is "another thread"? > Do you know whether myFaces (or richfaces) starts another thread? > I don't think that any other thrid party libs are involved here. > Any instant ideas for this? > > It's not a real problem so far because it occurred during a load test only. > > Michael > > > Am 09.04.2010 11:57, schrieb Jakob Korherr: > > Hi Michael, >> >> I just took a look at this problem and it seems to be one of tomcat. I >> also >> checked out the tomcat 6.0.24 branch to find the code that causes the >> exception. >> >> The main problem is that the request map is altered during it is processed >> with an Iterator in org.apache.catalina.util.Enumerator --> >> java.util.ConcurrentModificationException. >> >> Here is some code from tomcat that shows this conclusion: >> >> org.apache.catalina.connector.Request.getAttributeNames looks like this: >> >> public Enumeration getAttributeNames() { >> // cut for clarity >> return new Enumerator(attributes.keySet(), true); >> } >> >> So this code wants to create a new Enumerator with the keySet of the >> request >> attributes. It also tells the Enumerator to clone the keySet before >> generating the Iterator internally. The code that does the cloning can be >> found in org.apache.catalina.util.Enumerator: >> >> public Enumerator(Iterator iterator, boolean clone) { >> super(); >> if (!clone) { >> this.iterator = iterator; >> } else { >> List list = new ArrayList(); >> while (iterator.hasNext()) { >> list.add(iterator.next()); // line 101: this is the place >> where the ConcurrentModificationException happens >> } >> this.iterator = list.iterator(); >> } >> } >> >> So the constructor goes through the given Iterator (from the keySet of the >> request map) and creates an ArrayList out of it. The problem is now that >> if >> another thread alters the request map during this creation, you will get >> the >> ConcurrentModificationException. Of course, this is very rare and >> furthermore I guess the cloning was added to minimize the chance of a >> ConcurrentModificationException, but it still can happen. >> >> If you really want to eleminate this problem, thread synchronizing has to >> be >> introduced here. >> >> Regards, >> Jakob >> >> >> 2010/4/9 Michael Heinen<[email protected]> >> >> >> >>> Hi, >>> >>> I found followoing exception a few times in my tomcat log after running a >>> JMeter stresstest some hours with a few hundred users. >>> Any ideas about a ConcurrentModificationException during >>> RequestMap.getAttributeNames() ? >>> >>> [2010-04-07 09:00:59,653] http-8080-6 [ERROR] >>> [6799FA3FDEBB49F294E54657DB099957] servlets.FacesServletWrapper service: >>> Caught exception in the FacesServletWrapper: >>> javax.servlet.ServletException: java.util.ConcurrentModificationException >>> at >>> >>> javax.faces.webapp._ErrorPageWriter.throwException(_ErrorPageWriter.java:549) >>> at >>> >>> javax.faces.webapp.FacesServlet.handleLifecycleException(FacesServlet.java:293) >>> at javax.faces.webapp.FacesServlet.service(FacesServlet.java:187) >>> at >>> >>> com.foo.client.web.servlets.FacesServletWrapper.service(FacesServletWrapper.java:124) >>> at >>> >>> org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) >>> at >>> >>> org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) >>> at >>> org.ajax4jsf.webapp.BaseXMLFilter.doXmlFilter(BaseXMLFilter.java:206) >>> at org.ajax4jsf.webapp.BaseFilter.handleRequest(BaseFilter.java:290) >>> at >>> >>> org.ajax4jsf.webapp.BaseFilter.processUploadsAndHandleRequest(BaseFilter.java:388) >>> at org.ajax4jsf.webapp.BaseFilter.doFilter(BaseFilter.java:515) >>> at >>> >>> org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) >>> at >>> >>> org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) >>> at >>> >>> org.apache.myfaces.webapp.filter.ExtensionsFilter.doFilter(ExtensionsFilter.java:384) >>> at >>> >>> org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) >>> at >>> >>> org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) >>> at >>> com.foo.client.web.filters.LoginFilter.doFilter(LoginFilter.java:183) >>> at >>> >>> org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) >>> at >>> >>> org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) >>> at >>> >>> com.foo.client.web.filters.EncodingFilter.doFilter(EncodingFilter.java:49) >>> at >>> >>> org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) >>> at >>> >>> org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) >>> at >>> com.foo.client.web.filters.TimerFilter.doFilter(TimerFilter.java:71) >>> at >>> >>> org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) >>> at >>> >>> org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) >>> at >>> >>> org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) >>> at >>> >>> org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) >>> at >>> >>> org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:465) >>> at >>> >>> org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) >>> at >>> >>> org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) >>> at >>> >>> org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) >>> at >>> >>> org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) >>> at >>> >>> org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:852) >>> at >>> >>> org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) >>> at >>> org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) >>> at java.lang.Thread.run(Thread.java:619) >>> Caused by: javax.faces.FacesException: >>> java.util.ConcurrentModificationException >>> at >>> javax.faces.component.UIComponent.invokeOnComponent(UIComponent.java:166) >>> at >>> >>> javax.faces.component.UIComponentBase.invokeOnComponent(UIComponentBase.java:293) >>> at >>> javax.faces.component.UIComponent.invokeOnComponent(UIComponent.java:172) >>> at >>> >>> javax.faces.component.UIComponentBase.invokeOnComponent(UIComponentBase.java:293) >>> at >>> javax.faces.component.UIComponent.invokeOnComponent(UIComponent.java:172) >>> at >>> >>> javax.faces.component.UIComponentBase.invokeOnComponent(UIComponentBase.java:293) >>> at >>> javax.faces.component.UIComponent.invokeOnComponent(UIComponent.java:172) >>> at >>> >>> javax.faces.component.UIComponentBase.invokeOnComponent(UIComponentBase.java:293) >>> at >>> javax.faces.component.UIComponent.invokeOnComponent(UIComponent.java:172) >>> at >>> >>> javax.faces.component.UIComponentBase.invokeOnComponent(UIComponentBase.java:293) >>> at >>> org.ajax4jsf.component.AjaxViewRoot.processPhase(AjaxViewRoot.java:226) >>> at >>> >>> org.ajax4jsf.component.AjaxViewRoot.processValidators(AjaxViewRoot.java:463) >>> at >>> >>> org.apache.myfaces.lifecycle.ProcessValidationsExecutor.execute(ProcessValidationsExecutor.java:32) >>> at >>> >>> org.apache.myfaces.lifecycle.LifecycleImpl.executePhase(LifecycleImpl.java:103) >>> at >>> org.apache.myfaces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:76) >>> at >>> >>> org.apache.myfaces.custom.ppr.PPRLifecycleWrapper.execute(PPRLifecycleWrapper.java:68) >>> at javax.faces.webapp.FacesServlet.service(FacesServlet.java:178) >>> ... 32 more >>> Caused by: java.util.ConcurrentModificationException >>> at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793) >>> at java.util.HashMap$KeyIterator.next(HashMap.java:828) >>> at org.apache.catalina.util.Enumerator.<init>(Enumerator.java:101) >>> at org.apache.catalina.util.Enumerator.<init>(Enumerator.java:67) >>> at >>> org.apache.catalina.connector.Request.getAttributeNames(Request.java:962) >>> at >>> >>> org.apache.catalina.connector.RequestFacade.getAttributeNames(RequestFacade.java:278) >>> at >>> >>> org.apache.myfaces.context.servlet.RequestMap.getAttributeNames(RequestMap.java:66) >>> at >>> >>> org.apache.myfaces.util.AbstractAttributeMap$AbstractAttributeIterator.<init>(AbstractAttributeMap.java:196) >>> at >>> >>> org.apache.myfaces.util.AbstractAttributeMap$AbstractAttributeIterator.<init>(AbstractAttributeMap.java:194) >>> at >>> >>> org.apache.myfaces.util.AbstractAttributeMap$KeyIterator.<init>(AbstractAttributeMap.java:224) >>> at >>> >>> org.apache.myfaces.util.AbstractAttributeMap$KeyIterator.<init>(AbstractAttributeMap.java:224) >>> at >>> >>> org.apache.myfaces.util.AbstractAttributeMap$KeySet.iterator(AbstractAttributeMap.java:177) >>> at >>> >>> org.richfaces.component.ClonedObjectResolver.resolveCloned(ClonedObjectResolver.java:92) >>> at >>> >>> org.richfaces.component.ClonedObjectResolver.getValue(ClonedObjectResolver.java:61) >>> at javax.el.CompositeELResolver.getValue(CompositeELResolver.java:54) >>> at javax.el.CompositeELResolver.getValue(CompositeELResolver.java:54) >>> at >>> >>> org.apache.myfaces.el.unified.resolver.FacesCompositeELResolver.getValue(FacesCompositeELResolver.java:140) >>> at org.apache.el.parser.AstIdentifier.getValue(AstIdentifier.java:61) >>> at org.apache.el.parser.AstValue.getValue(AstValue.java:107) >>> at >>> org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:186) >>> at >>> >>> org.apache.jasper.el.JspValueExpression.getValue(JspValueExpression.java:101) >>> at >>> >>> javax.faces.component._ComponentUtils.getExpressionValue(_ComponentUtils.java:236) >>> at >>> >>> javax.faces.component.UIComponentBase.getExpressionValue(UIComponentBase.java:1176) >>> at >>> >>> javax.faces.component.UIComponentBase.isRendered(UIComponentBase.java:1251) >>> at >>> >>> org.apache.myfaces.custom.htmlTag.AbstractHtmlTag.isRendered(AbstractHtmlTag.java:84) >>> at >>> >>> org.apache.myfaces.custom.datalist.AbstractHtmlDataList.processChildren(AbstractHtmlDataList.java:149) >>> at >>> >>> org.apache.myfaces.custom.datalist.AbstractHtmlDataList.processValidators(AbstractHtmlDataList.java:108) >>> at >>> >>> javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:726) >>> at >>> >>> javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:726) >>> at >>> >>> javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:726) >>> at >>> >>> javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:726) >>> at >>> >>> javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:726) >>> at javax.faces.component.UIForm.processValidators(UIForm.java:82) >>> at >>> >>> org.ajax4jsf.component.AjaxViewRoot$3.invokeContextCallback(AjaxViewRoot.java:447) >>> at >>> >>> org.ajax4jsf.component.ContextCallbackWrapper.invokeContextCallback(ContextCallbackWrapper.java:44) >>> at >>> javax.faces.component.UIComponent.invokeOnComponent(UIComponent.java:163) >>> ... 48 more >>> >>> I do not start a new thread during request processing and therefore I >>> don't >>> have any idea about the concurrent modification on Request level. >>> >>> Is this rather an application issue, a myfaces issue, a richfaces issue >>> or >>> a tomcat issue? >>> I can't reproduce this manually of course. >>> >>> Environment: >>> myFaces 1.2.8 >>> richfaces 3.3.3 >>> jsps, no facelets >>> Tomcat 6.0.24 >>> jdk 1.6.0.16 >>> >>> Michael >>> >>> >>> >>> >> >> >> > > -- Jakob Korherr blog: http://www.jakobk.com twitter: http://twitter.com/jakobkorherr work: http://www.irian.at
