[ http://issues.apache.org/jira/browse/TAPESTRY-276?page=all ]
Howard M. Lewis Ship resolved TAPESTRY-276:
-------------------------------------------
Resolution: Invalid
Assign To: Howard M. Lewis Ship
> NullPointerException in AbstractEngine under high load
> ------------------------------------------------------
>
> Key: TAPESTRY-276
> URL: http://issues.apache.org/jira/browse/TAPESTRY-276
> Project: Tapestry
> Type: Bug
> Components: Framework
> Versions: 3.0.1
> Environment: J2SDK 1.4.2_06, Tomcat 5.0.28, Solaris 2.8, Tapestry 3.0.1
> Web application using many assets for images and css files.
> Reporter: Michael Echerer
> Assignee: Howard M. Lewis Ship
> Priority: Critical
>
> While load testing our application we detected that the AbstractEngine threw
> NullPointerExceptions wrapped in ServletExceptions. Our load testing software
> shows that those errors pop up when loading CSS or image files randomly which
> use the AssetService (/app?service=asset...). The visual effect or missing
> images, resp. CSS styles because HTTP 500 internal server errors occur as we
> can reproduce it less frequently with a browser, too.
> javax.servlet.ServletException
>
> java.lang.NullPointerException
> org.apache.tapestry.engine.AbstractEngine.activateExceptionPage(AbstractEngine.java:453)
> org.apache.tapestry.engine.AbstractEngine.service(AbstractEngine.java:914)
> org.apache.tapestry.ApplicationServlet.doService(ApplicationServlet.java:197)
> org.apache.tapestry.ApplicationServlet.doGet(ApplicationServlet.java:158)
> javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
> javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
> We think the bug is in
> public boolean service(RequestContext context) throws ServletException,
> IOException
> the IRequestCycle cycle = null; and under rare circumstances it might stay
> null and produces the NullPointerException that even prevents the error page
> to be activated.
> Probably some race condition in service.getService(serviceName), e.g. the
> _serviceMap in servletContext or something around.
> We didn't yet trace down the service method and why it can throw an
> exception, that is first catched but thrown again. Unfortunately it cascades
> in a way that it's possible for the cycle to stay null. This breaks the
> exception page mechanismn as it needs a cycle at least.
> The last catch block in service() uses the cycle that may never been set to
> non null.
> activateExceptionPage(cycle, output, ex);
> The initial exception seems to be caused by means to determine a service.
> Which explains why it might happen only in one of our application that makes
> heavy use of assets. (although the other apps are quite similar and build
> upon common components, but not as complex).
> Further details will follow... We'll first try to override the service method
> in our application with a simple synchronized block calling super.service().
> If the problem disappear this would point towards a threading issue.
> Cheers,
> Michael
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