error page servlet register twice

[Nhut Thai Le]

Hello,

We are using pax-web-extender-whiteboard 7.2.4 on equinox and I have a few error page servlet annotated as followed:

@Component(

service = Servlet.class,

property = {

HttpWhiteboardConstants.HTTP_WHITEBOARD_SERVLET_NAME + "=Error403Servlet",

"alias=/error403",

"osgi.http.whiteboard.servlet.errorPage=403",

"osgi.http.whiteboard.context.select=(osgi.http.whiteboard.context.name=WebviewerServletContextHelper)"

},

scope = ServiceScope.PROTOTYPE

)

public final class Error403Servlet extends HttpServlet {...}

However, sometimes when we start the server, we got this error:

java.lang.IllegalArgumentException: Error page for [403] already registered.
	at org.ops4j.pax.web.service.spi.model.ServiceModel.addErrorPageModel(ServiceModel.java:315)
	at org.ops4j.pax.web.service.internal.HttpServiceStarted.registerErrorPage(HttpServiceStarted.java:961)
	at org.ops4j.pax.web.service.internal.HttpServiceProxy.registerErrorPage(HttpServiceProxy.java:343)
	at org.ops4j.pax.web.extender.whiteboard.internal.element.ServletWebElement.register(ServletWebElement.java:107)
	at org.ops4j.pax.web.extender.whiteboard.internal.WebApplication.registerWebElement(WebApplication.java:392)
	at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(Unknown Source)
	at java.util.stream.ReferencePipeline$2$1.accept(Unknown Source)
	at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(Unknown Source)
	at java.util.stream.AbstractPipeline.copyInto(Unknown Source)
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(Unknown Source)
	at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(Unknown Source)
	at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(Unknown Source)
	at java.util.stream.AbstractPipeline.evaluate(Unknown Source)
	at java.util.stream.ReferencePipeline.forEach(Unknown Source)
	at org.ops4j.pax.web.extender.whiteboard.internal.WebApplication.addWebElement(WebApplication.java:170)
	at org.ops4j.pax.web.extender.whiteboard.internal.tracker.AbstractTracker.addingService(AbstractTracker.java:193)
	at org.ops4j.pax.web.extender.whiteboard.internal.tracker.AbstractTracker.addingService(AbstractTracker.java:46)
	at org.osgi.util.tracker.ServiceTracker$Tracked.customizerAdding(ServiceTracker.java:941)
	at org.osgi.util.tracker.ServiceTracker$Tracked.customizerAdding(ServiceTracker.java:1)
	at org.osgi.util.tracker.AbstractTracked.trackAdding(AbstractTracked.java:256)
	at org.osgi.util.tracker.AbstractTracked.track(AbstractTracked.java:229)
	at org.osgi.util.tracker.ServiceTracker$Tracked.serviceChanged(ServiceTracker.java:901)
	at org.eclipse.osgi.internal.serviceregistry.FilteredServiceListener.serviceChanged(FilteredServiceListener.java:109)
	at org.eclipse.osgi.internal.framework.BundleContextImpl.dispatchEvent(BundleContextImpl.java:920)
	at org.eclipse.osgi.framework.eventmgr.EventManager.dispatchEvent(EventManager.java:230)
	at org.eclipse.osgi.framework.eventmgr.ListenerQueue.dispatchEventSynchronous(ListenerQueue.java:148)
	at org.eclipse.osgi.internal.serviceregistry.ServiceRegistry.publishServiceEventPrivileged(ServiceRegistry.java:862)
	at org.eclipse.osgi.internal.serviceregistry.ServiceRegistry.publishServiceEvent(ServiceRegistry.java:801)
	at org.eclipse.osgi.internal.serviceregistry.ServiceRegistrationImpl.register(ServiceRegistrationImpl.java:127)
	at org.eclipse.osgi.internal.serviceregistry.ServiceRegistry.registerService(ServiceRegistry.java:225)
	at org.eclipse.osgi.internal.framework.BundleContextImpl.registerService(BundleContextImpl.java:469)
	at org.apache.felix.scr.impl.manager.AbstractComponentManager$3.register(AbstractComponentManager.java:887)
	at org.apache.felix.scr.impl.manager.AbstractComponentManager$3.register(AbstractComponentManager.java:874)
	at org.apache.felix.scr.impl.manager.RegistrationManager.changeRegistration(RegistrationManager.java:132)
	at org.apache.felix.scr.impl.manager.AbstractComponentManager.registerService(AbstractComponentManager.java:941)
	at org.apache.felix.scr.impl.manager.AbstractComponentManager.activateInternal(AbstractComponentManager.java:741)
	at org.apache.felix.scr.impl.manager.AbstractComponentManager.enableInternal(AbstractComponentManager.java:675)
	at org.apache.felix.scr.impl.manager.AbstractComponentManager.enable(AbstractComponentManager.java:430)
	at org.apache.felix.scr.impl.manager.ConfigurableComponentHolder.enableComponents(ConfigurableComponentHolder.java:657)
	at org.apache.felix.scr.impl.BundleComponentActivator.initialEnable(BundleComponentActivator.java:341)
	at org.apache.felix.scr.impl.Activator.loadComponents(Activator.java:390)
	at org.apache.felix.scr.impl.Activator.access$200(Activator.java:54)
	at org.apache.felix.scr.impl.Activator$ScrExtension.start(Activator.java:265)
	at org.apache.felix.utils.extender.AbstractExtender.createExtension(AbstractExtender.java:254)
	at org.apache.felix.utils.extender.AbstractExtender.modifiedBundle(AbstractExtender.java:227)
	at org.apache.felix.utils.extender.AbstractExtender.addingBundle(AbstractExtender.java:187)
	at org.osgi.util.tracker.BundleTracker$Tracked.customizerAdding(BundleTracker.java:469)
	at org.osgi.util.tracker.BundleTracker$Tracked.customizerAdding(BundleTracker.java:1)
	at org.osgi.util.tracker.AbstractTracked.trackAdding(AbstractTracked.java:256)
	at org.osgi.util.tracker.AbstractTracked.track(AbstractTracked.java:229)
	at org.osgi.util.tracker.BundleTracker$Tracked.bundleChanged(BundleTracker.java:444)
	at org.eclipse.osgi.internal.framework.BundleContextImpl.dispatchEvent(BundleContextImpl.java:908)
	at org.eclipse.osgi.framework.eventmgr.EventManager.dispatchEvent(EventManager.java:230)
	at org.eclipse.osgi.framework.eventmgr.ListenerQueue.dispatchEventSynchronous(ListenerQueue.java:148)
	at org.eclipse.osgi.internal.framework.EquinoxEventPublisher.publishBundleEventPrivileged(EquinoxEventPublisher.java:213)
	at org.eclipse.osgi.internal.framework.EquinoxEventPublisher.publishBundleEvent(EquinoxEventPublisher.java:120)
	at org.eclipse.osgi.internal.framework.EquinoxEventPublisher.publishBundleEvent(EquinoxEventPublisher.java:112)
	at org.eclipse.osgi.internal.framework.EquinoxContainerAdaptor.publishModuleEvent(EquinoxContainerAdaptor.java:168)
	at org.eclipse.osgi.container.Module.publishEvent(Module.java:476)
	at org.eclipse.osgi.container.Module.doStart(Module.java:578)
	at org.eclipse.osgi.container.Module.start(Module.java:449)
	at org.eclipse.osgi.container.ModuleContainer$ContainerStartLevel.incStartLevel(ModuleContainer.java:1628)
	at org.eclipse.osgi.container.ModuleContainer$ContainerStartLevel.incStartLevel(ModuleContainer.java:1608)
	at org.eclipse.osgi.container.ModuleContainer$ContainerStartLevel.doContainerStartLevel(ModuleContainer.java:1579)
	at org.eclipse.osgi.container.ModuleContainer$ContainerStartLevel.dispatchEvent(ModuleContainer.java:1522)
	at org.eclipse.osgi.container.ModuleContainer$ContainerStartLevel.dispatchEvent(ModuleContainer.java:1)
	at org.eclipse.osgi.framework.eventmgr.EventManager.dispatchEvent(EventManager.java:230)
	at org.eclipse.osgi.framework.eventmgr.EventManager$EventThread.run(EventManager.java:340)

Since the error page is working fine despite this exception, is it a race condition in the service registry that cause this exception? Should this be reported as bug on pax-web or felix scr? We tried to upgrade to pax-web 7.2.10 but still got the same error from time to time

Thai Le

[Grzegorz Grzybek]

Hello Thai

Finally I have some time to tackle all your recent emails related to pax-web. Expect some answers soon.

regards

Grzegorz Grzybek

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[Grzegorz Grzybek]

Hello

We have:

 – org.ops4j.pax.web.itest.undertow.WhiteboardR6IntegrationTest#testErrorServlet

 – org.ops4j.pax.web.itest.jetty.WhiteboardR6IntegrationTest#testErrorServlet

 – org.ops4j.pax.web.itest.tomcat.WhiteboardR6IntegrationTest#testErrorServlet

which tests servlet with "osgi.http.whiteboard.servlet.errorPage = [ "404", "442", "5xx", "java.io.IOException" ]". This test never failed with such exception...

Questions:

 – did you try debugging and checking what's passed in org.ops4j.pax.web.service.spi.model.ServiceModel#addErrorPageModel? (e.g., value of org.ops4j.pax.web.service.spi.model.ContextModel#classLoader) inside ErrorModel?

 – why do you use scope = prototype?

regards

Grzegorz Grzybek

wt., 3 wrz 2019 o 16:46 Nhut Thai Le <nt...@castortech.com> napisał(a):

[Nhut Thai Le]

Hello,

I'll put the breakpoint at addErrorPageModel and check the value when this error happen again.

About the prototype, i use it because both R6 and R7 recommends in section 140.5

Thai

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[Nhut Thai Le]

Hi Grzegorz,

Here are some screenshot showing the same 403 error page registered twice, both times they are using the same classLoader:

This is the 1st time the 403 got registered, there was nothing in the erroPageModels map, class loader of the ErrorPageModel is bundle 29

This is the 2nd time the 403 error page got registered, as you can see, there is already one 403 error page in the errorPageModels map with different id

and it is using the same classloader 

What should be my next step to debug this?

Thai

[Jean-Baptiste Onofré]

Hi

Is it not the same issue I fixed for the servlet context ? (Service registered twice)

Did you try on Karaf 4.2.6 ?

Regards

JB

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[Nhut Thai Le]

Hi JB,

I'm running this on equinox from eclipse osgi launch, haven't try it on karaf yet. Do you have a reference to the bug you fixed ?

Thai

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[Jean-Baptiste Onofré]

Let me find jira and commit id.

Regards

JB

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[Grzegorz Grzybek]

Thai, good investigation

So when we're already in the debugger, please:

 - put a breakpoint in ErrorPageModel constructor

 - when its hit, show me the stacktrace

So - each time ErrorPageModel is constructed, collect the thread trace that constructs this model - we can try finding the reasons of duplicate creation. Discovering that it's "added" to models is only a consequence. Now we should find the reason ;).

regards

Grzegorz Grzybek

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[Nhut Thai Le]

Hi Grzegorz,

Thank you for looking into this, here is the call stack from the 1st call to ErrorPageModel constructor for 403:

and below is the 2nd time, since the call stack for the 2nd hit is quite long, i took 2 screenshots:

Please let me know if you need more info

Thai

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[Grzegorz Grzybek]

I'll analyze the screenshots tomorrow. But please - is there a chance to "copy stack trace" from eclipse debugger? (it can be done in IDEA)...

regards

Grzegorz Grzybek

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[Nhut Thai Le]

Hi Grzegorz,

I didnt know i can copy stacktrace as txt. I tried again to get the call stack but i dont get the 2nd registration of 403 anymore, I have tried 5 times. As this is not always reproducible, i'll keep an eye on it and post back the txt version of the call stack when i got the error again. In the meantime, the call stack of the 2nd registration of 403 is in the screenshot i sent earlier.

Thai

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[Grzegorz Grzybek]

Hello

I analyzed the screenshots of stack traces and there are two paths where the same error page model is registered:

 - normal path, where SCR @Component activation registers Servlet.class service that leads to registration of ErrorPageModel - tha's fine

 - 2nd path, where org.ops4j.pax.web.extender.whiteboard.internal.WebApplication#setServletContextHelper() is called upon detection of org.osgi.service.http.context.ServletContextHelper OSGi service

In 2nd path, org.ops4j.pax.web.extender.whiteboard.internal.WebApplication#setServletContextHelper() is called, but it first should call org.ops4j.pax.web.extender.whiteboard.internal.WebApplication#unregisterHttpContext() to unregister existing elements.

The problem I sense is that org.ops4j.pax.web.extender.whiteboard.internal.WebApplication#hasHttpContextMapping() probably returns "false" somehow, so there's no registration.

+Jean-Baptiste Onofré do you remember something related to duplicate registration? PAXWEB-1197 was about session listeners only...

Thai - can you create PAXWEB issue, so we can track the problem there?

regards

Grzegorz Grzybek

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[Nhut Thai Le]

Hi guys,

I open the bug for this issue:

https://ops4j1.jira.com/projects/PAXWEB/issues/PAXWEB-1235  

Thank you again for looking at this.

Thai

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