https://issues.apache.org/bugzilla/show_bug.cgi?id=54534
Bug ID: 54534
Summary: JMX connection may load servlet with invalid
ClassLoader
Product: Tomcat 7
Version: 7.0.35
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P2
Component: Catalina
Assignee: dev@tomcat.apache.org
Reporter: robby.mor...@bazaarvoice.com
Classification: Unclassified
Created attachment 29929
--> https://issues.apache.org/bugzilla/attachment.cgi?id=29929&action=edit
Project for reproduction of bug
I've recently observed a bug in Tomcat 7 that is causing our servers to fail to
start-up, with the root cause being that, in response to a JMX request, Tomcat
7 is loading our servlet on a Thread whose contextClassLoader is NOT that of
the web application. This may lead to various problems; in our case, it leads
to failure of Spring to find the requisite XSDs that are present in jars in our
web app's WEB-INF/lib directory.
Here is the stack trace that is reported for Tomcat7.0.35 + Spring 3.1.1:
org.springframework.beans.factory.parsing.BeanDefinitionParsingException:
Configuration problem: Unable to locate Spring NamespaceHandler for XML schema
namespace [http://www.springframework.org/schema/context]
Offending resource: ServletContext resource [/WEB-INF/spring-servlet.xml]
at
org.springframework.beans.factory.parsing.FailFastProblemReporter.error(FailFastProblemReporter.java:68)
at
org.springframework.beans.factory.parsing.ReaderContext.error(ReaderContext.java:85)
at
org.springframework.beans.factory.parsing.ReaderContext.error(ReaderContext.java:80)
at
org.springframework.beans.factory.xml.BeanDefinitionParserDelegate.error(BeanDefinitionParserDelegate.java:316)
at
org.springframework.beans.factory.xml.BeanDefinitionParserDelegate.parseCustomElement(BeanDefinitionParserDelegate.java:1416)
at
org.springframework.beans.factory.xml.BeanDefinitionParserDelegate.parseCustomElement(BeanDefinitionParserDelegate.java:1409)
at
org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.parseBeanDefinitions(DefaultBeanDefinitionDocumentReader.java:184)
at
org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.doRegisterBeanDefinitions(DefaultBeanDefinitionDocumentReader.java:140)
at
org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.registerBeanDefinitions(DefaultBeanDefinitionDocumentReader.java:111)
at
org.springframework.beans.factory.xml.XmlBeanDefinitionReader.registerBeanDefinitions(XmlBeanDefinitionReader.java:493)
at
org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadBeanDefinitions(XmlBeanDefinitionReader.java:390)
at
org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:334)
at
org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:302)
at
org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:174)
at
org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:209)
at
org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:180)
at
org.springframework.web.context.support.XmlWebApplicationContext.loadBeanDefinitions(XmlWebApplicationContext.java:125)
at
org.springframework.web.context.support.XmlWebApplicationContext.loadBeanDefinitions(XmlWebApplicationContext.java:94)
at
org.springframework.context.support.AbstractRefreshableApplicationContext.refreshBeanFactory(AbstractRefreshableApplicationContext.java:131)
at
org.springframework.context.support.AbstractApplicationContext.obtainFreshBeanFactory(AbstractApplicationContext.java:522)
at
org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:436)
at
org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:631)
at
org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:588)
at
org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:645)
at
org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:508)
at
org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:449)
at
org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:133)
at javax.servlet.GenericServlet.init(GenericServlet.java:160)
at
org.apache.catalina.core.StandardWrapper.initServlet(StandardWrapper.java:1274)
at
org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1186)
at
org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:858)
at
org.apache.catalina.core.StandardWrapper.isSingleThreadModel(StandardWrapper.java:592)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at
org.apache.tomcat.util.modeler.BaseModelMBean.getAttribute(BaseModelMBean.java:190)
at
org.apache.tomcat.util.modeler.BaseModelMBean.getAttributes(BaseModelMBean.java:234)
at
com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.getAttributes(DefaultMBeanServerInterceptor.java:726)
at
com.sun.jmx.mbeanserver.JmxMBeanServer.getAttributes(JmxMBeanServer.java:665)
at
javax.management.remote.rmi.RMIConnectionImpl.doOperation(RMIConnectionImpl.java:1408)
at
javax.management.remote.rmi.RMIConnectionImpl.access$200(RMIConnectionImpl.java:72)
at
javax.management.remote.rmi.RMIConnectionImpl$PrivilegedOperation.run(RMIConnectionImpl.java:1265)
at
javax.management.remote.rmi.RMIConnectionImpl.doPrivilegedOperation(RMIConnectionImpl.java:1360)
at
javax.management.remote.rmi.RMIConnectionImpl.getAttributes(RMIConnectionImpl.java:636)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:303)
at sun.rmi.transport.Transport$1.run(Transport.java:159)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:155)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:535)
at
sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:790)
at
sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:649)
at
java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:680)
I've attached a simple Maven-based WAR project that can reproduce this -- see
the README for exact steps.
In this case, the exception will occur, but after the artificially imposed 30
second delay completes, the servlet appears to load fine.
In our actual systems, the servlet appears to remain in an incompletely loaded
state. My hypothesis is that this is timing-related... if
StandardWrapper.allocate does not complete before the main thread that is
loading the web application correctly, then I think the main thread adds a
reference to the mis-loaded servlet, and the subsequent deallocate call in
StandardWrapper.isSingleThreadModel does not unload the servlet, causing it to
remain in its impaired state.
Please investigate this bug, since it is likely to affect users combining
Tomcat + Spring WebMVC + JMX monitoring, which I believe to be a common use
case.
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