[
https://issues.apache.org/jira/browse/CXF-8590?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17408365#comment-17408365
]
Freeman Yue Fang commented on CXF-8590:
---------------------------------------
I think the root cause is that the Xerces Dom implementation isn't thread safe,
please see
https://xerces.apache.org/xerces2-j/faq-dom.html
{code}
s Xerces DOM implementation thread-safe?
No. DOM does not require implementations to be thread safe. If you need to
access the DOM from multiple threads, you are required to add the appropriate
locks to your application code.
{code}
So add the appropriate locks to application code should be the way to go.
Of course ideally we can add the synchronized locks in Apache neethi code,
which is closer to the root of stackrtrace. But I'm also thinking to fix it in
CXF codebase, at least before the fix available in Apache neethi.
Freeman
> First invocation of method causes NPE failure in neethi.PolicyBuilder
> ---------------------------------------------------------------------
>
> Key: CXF-8590
> URL: https://issues.apache.org/jira/browse/CXF-8590
> Project: CXF
> Issue Type: Bug
> Components: Core, WS-* Components
> Affects Versions: 3.4.4
> Reporter: Kim Johan Andersson
> Priority: Major
>
> I have a multithreaded application where each thread does the following:
> new SomeService
> .getPort()
> .invokeSomeEndpointMethod()
>
> The first invocation of the endpoint method cases the following error:
> {noformat}
> java.lang.reflect.InvocationTargetException
> 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:498)
> at
> org.apache.neethi.builders.converters.ConverterRegistry.findQName(ConverterRegistry.java:121)
> at
> org.apache.neethi.PolicyBuilder.processOperationElement(PolicyBuilder.java:204)
> at
> org.apache.neethi.PolicyBuilder.getPolicyOperator(PolicyBuilder.java:174)
> at org.apache.neethi.PolicyBuilder.getPolicy(PolicyBuilder.java:124)
> at
> org.apache.cxf.ws.policy.attachment.wsdl11.Wsdl11AttachmentPolicyProvider.getElementPolicy(Wsdl11AttachmentPolicyProvider.java:192)
> at
> org.apache.cxf.ws.policy.attachment.wsdl11.Wsdl11AttachmentPolicyProvider.getElementPolicy(Wsdl11AttachmentPolicyProvider.java:168)
> at
> org.apache.cxf.ws.policy.attachment.wsdl11.Wsdl11AttachmentPolicyProvider.getElementPolicy(Wsdl11AttachmentPolicyProvider.java:161)
> at
> org.apache.cxf.ws.policy.attachment.wsdl11.Wsdl11AttachmentPolicyProvider.getEffectivePolicy(Wsdl11AttachmentPolicyProvider.java:75)
> at
> org.apache.cxf.ws.policy.PolicyEngineImpl.getAggregatedServicePolicy(PolicyEngineImpl.java:461)
> at
> org.apache.cxf.ws.policy.EndpointPolicyImpl.initializePolicy(EndpointPolicyImpl.java:151)
> at
> org.apache.cxf.ws.policy.EndpointPolicyImpl.initialize(EndpointPolicyImpl.java:140)
> at
> org.apache.cxf.ws.policy.PolicyEngineImpl.createEndpointPolicyInfo(PolicyEngineImpl.java:614)
> at
> org.apache.cxf.ws.policy.PolicyEngineImpl.getEndpointPolicy(PolicyEngineImpl.java:326)
> at
> org.apache.cxf.ws.policy.PolicyEngineImpl.getClientEndpointPolicy(PolicyEngineImpl.java:313)
> at
> org.apache.cxf.ws.policy.PolicyDataEngineImpl.getClientEndpointPolicy(PolicyDataEngineImpl.java:61)
> at
> org.apache.cxf.transport.http.HTTPConduit.updateClientPolicy(HTTPConduit.java:326)
> at
> org.apache.cxf.transport.http.HTTPConduit.updateClientPolicy(HTTPConduit.java:346)
> at
> org.apache.cxf.transport.http.HTTPConduit.getClient(HTTPConduit.java:892)
> at
> org.apache.cxf.transport.http.HTTPConduit.configureConduitFromEndpointInfo(HTTPConduit.java:368)
> at
> org.apache.cxf.transport.http.HTTPConduit.finalizeConfig(HTTPConduit.java:448)
> at
> org.apache.cxf.transport.http.HTTPTransportFactory.getConduit(HTTPTransportFactory.java:249)
> at
> org.apache.cxf.binding.soap.SoapTransportFactory.getConduit(SoapTransportFactory.java:226)
> at
> org.apache.cxf.binding.soap.SoapTransportFactory.getConduit(SoapTransportFactory.java:233)
> at
> org.apache.cxf.endpoint.AbstractConduitSelector.createConduit(AbstractConduitSelector.java:144)
> at
> org.apache.cxf.endpoint.AbstractConduitSelector.getSelectedConduit(AbstractConduitSelector.java:108)
> at
> org.apache.cxf.endpoint.UpfrontConduitSelector.prepare(UpfrontConduitSelector.java:63)
> at
> org.apache.cxf.endpoint.ClientImpl.prepareConduitSelector(ClientImpl.java:887)
> at org.apache.cxf.endpoint.ClientImpl.doInvoke(ClientImpl.java:525)
> at org.apache.cxf.endpoint.ClientImpl.invoke(ClientImpl.java:441)
> at org.apache.cxf.endpoint.ClientImpl.invoke(ClientImpl.java:356)
> at org.apache.cxf.endpoint.ClientImpl.invoke(ClientImpl.java:314)
> at org.apache.cxf.frontend.ClientProxy.invokeSync(ClientProxy.java:96)
> at
> org.apache.cxf.jaxws.JaxWsClientProxy.invoke(JaxWsClientProxy.java:140)
> ...
> at
> org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:573)
> Caused by: java.lang.NullPointerException
> at
> com.sun.org.apache.xerces.internal.dom.DeferredElementNSImpl.synchronizeData(DeferredElementNSImpl.java:108)
> at
> com.sun.org.apache.xerces.internal.dom.ElementNSImpl.getLocalName(ElementNSImpl.java:338)
> at
> org.apache.neethi.builders.converters.AbstractDOMConverter.getQName(AbstractDOMConverter.java:43)
> ... 45 more
> {noformat}
>
> From there on, everything works fine. The service in question uses policies,
> and apparently policies are lazily initialized.
> The actual failure is triggered by a race condition causing ElementNSImpl
> from xerces to be being shared across threads as a consequence.
> This happens in
> org.apache.cxf.ws.policy.attachment.wsdl11.Wsdl11AttachmentPolicyProvider.getElementPolicy,
> when the PolicyRegistry is consulted:
> {noformat}
> Policy policy = registry.lookup(id);
> if (policy == null) {
> try {
> policy = builder.getPolicy(e.getElement());
> {noformat}
>
> All threads will start building the missing policy, as there is nothing in
> the registry and no synchronization on a cache miss. Some thread wins the
> race and gets a usable result from e.getElement() and stores the result in
> the registry, the others hit the NPE-error.
> I do not really understand all the internal workings, but I can cure this
> problem by changing the code snippet to:
> {noformat}
> synchronized (e.getElement()) {
> Policy policy = registry.lookup(id);
> if (policy == null) {
> try {
> policy = builder.getPolicy(e.getElement());
>
> ...
> }
> {noformat}
> That solves the race to initialize the entry in the registry, but not the
> real problem.
> This leaves me with 3 questions:
> Is there a way to eagerly populate the PolicyRegistry as an user of CXF?
> Shouldn't Wsdl11AttachmentPolicyProvider be thread safe, if policies are to
> be lazily initialized?
> How do we prevent the WSDLManager in the Service from sharing non-tread safe
> items (ElementNSImpl) across threads?
> Apparently org.apache.cxf.jaxws.ServiceImpl.initialize always selects the
> same bus, which cases the WSDLManager to be shared between threads. Normally
> that would be a good thing, since we can share the WSDL-cache.
> I tried to build a test-case, so far I have no luck in building the required
> configuration. Also, which submodule is to blame here? A lot of components
> are involved.
> Please ask for more details if required.
> Thanks,
> Kim Johan Andersson
>
>
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
