org.codehaus.xfire.util.jdom.StaxBuilder.buildTree causing infinite loop in
HashMap.get().
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Key: XFIRE-993
URL: http://jira.codehaus.org/browse/XFIRE-993
Project: XFire
Issue Type: Bug
Components: Aegis Module
Affects Versions: 1.2.4
Reporter: Karthikeyan M.
Assignee: Dan Diephouse
* Large number (>50) of threads on the server were stuck with infinite loop in
HashMap.get(). Sample stack trace attached below:
Thread: http-0.0.0.0-8080-1 : priority:5, demon:true, threadId:54,
threadState:RUNNABLE, threadLockName:null
java.util.HashMap.get(HashMap.java:329)
org.jdom.Namespace.getNamespace(Namespace.java:148)
org.jdom.UncheckedJDOMFactory.element(UncheckedJDOMFactory.java:40)
org.codehaus.xfire.util.jdom.StaxBuilder.buildTree(StaxBuilder.java:348)
org.codehaus.xfire.util.jdom.StaxBuilder.build(StaxBuilder.java:215)
org.codehaus.xfire.soap.handler.ReadHeadersHandler.readHeaders(ReadHeadersHandler.java:131)
org.codehaus.xfire.soap.handler.ReadHeadersHandler.invoke(ReadHeadersHandler.java:59)
org.codehaus.xfire.handler.HandlerPipeline.invoke(HandlerPipeline.java:98)
org.codehaus.xfire.transport.DefaultEndpoint.onReceive(DefaultEndpoint.java:61)
org.codehaus.xfire.transport.AbstractChannel.receive(AbstractChannel.java:38)
org.codehaus.xfire.transport.http.XFireServletController.invoke(XFireServletController.java:278)
org.codehaus.xfire.transport.http.XFireServletController.doService(XFireServletController.java:144)
com.yahoo.sm.ws.servlet.XFireRequestProcessor.process(XFireRequestProcessor.java:40)
* HashMap.get() can cause infinite loop, if it is not synchronized correctly.
(ref:
http://blogs.opensymphony.com/plightbo/2005/07/hashmapget_can_cause_an_infini.html)
* Xfire ends up calling Namespace.getNamespace() through
UncheckedJDOMFactory.element(), which is not threadsafe.
* Namespace.getNamespace() is a static method that gets OR creates the
Namespace object. When creating the Namespace object, it is cached in an
internal static HashMap, without any synchronization. When
Namespace.getNamespace() is called in multiple threads, it corrupts the static
'namespaces' HashMap in org.jdom.Namespace, resulting in infinite loop in later
calls.
* This would essentially mean jdom can not be used in an application running
multiple threads. Can xfire use a safer approach for building header tree?
* one workaround is to synchronize around Namespace instance creation outside
of jdom and make sure all element creation goes through it.
Ex:
public static Element createJDOMElement(JDOMFactory f, String elementName,
String elemPrefix, String nsURI)
{
Namespace ns = initJDOMNamespace(elemPrefix, nsURI);
return f.element(elementName, ns);
}
// workaround to synchronize initialization of static 'namespaces' HashMap
// in org.jdom.Namespace class.
public static synchronized Namespace initJDOMNamespace(String elemPrefix,
String nsURI)
{
return Namespace.getNamespace(elemPrefix, nsURI);
}
and use createJDOMElement for all jdom element creation inside XFire.
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