PK71789; 7.0: intermittent nullpointerexception in finishresponsemessage

Download Description

PK71789 resolves the following problem:

ERROR DESCRIPTION:
When multiple Asynchronous Request Dispatcher (ARD) clients are used to stress the server, some intermittent NullPointerExceptions occur.

USERS AFFECTED:
Users of IBM® WebSphere® Application Server Version 7.0.0.0

PROBLEM DESCRIPTION:
This APAR covers several related WebContainer problems as described below.

RECOMMENDATION:
None

1. When multiple Asynchronous Request Dispatcher (ARD) clients are used to stress the server, some intermittent NullPointerExceptions occur. The partial stack is shown here.


[8/19/08 14:11:00:585 CDT] 0000004b channel E
com.ibm.ws.webcontainer.channel.WCChannelLink finishBufferAsynch


Exception in finishBufferAsynch: java.lang.NullPointerException
at com.ibm.ws.ard.channel.ARDHttpServiceContext.finishResponseMessage
(ARDHttpServiceContext.java:136)
at com.ibm.ws.webcontainer.channel.WCChannelLink.finishBufferAsynch
(WCChannelLink.java:483)
at com.ibm.ws.webcontainer.channel.WCChannelLink.ready
(WCChannelLink.java:198)
at com.ibm.ws.ard.channel.ARDChannelConnLink.handleDiscrimination
(ARDChannelConnLink.java:183
at com.ibm.ws.ard.channel.ARDChannelConnLink.ready
(ARDChannelConnLink.java:90)


2. The client side aggregation feature of ARD fails when running through the WebSphere proxy. No output is shown.

3. ARD with Dynamic Caching enabled fails sometimes with a NullPointerException like the following:


[9/10/08 10:53:33:376 CDT] 00000037 servlet E
com.ibm.ws.webcontainer.servlet.ServletWrapper service
SRVE0068E: Uncaught exception created in one of the service methods
of the servlet /ARDPriceQuoteJSPAutoGen.jsp in application
ERWW_Pyxis_08_16_2008e.
Exception created : java.lang.NullPointerException
at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:779)
at com.ibm.ws.cache.servlet.FragmentComposer.
getARDChildFragmentComposer
(FragmentComposer.java:1915)
at com.ibm.ws.cache.servlet.CacheARDHook.returnARDChild
(CacheARDHook.java:171)
at com.ibm.ws.cache.servlet.CacheHook.cleanup
(CacheHook.java:304)
at com.ibm.ws.cache.servlet.CacheHook.handleServlet
(CacheHook.java:259)
at com.ibm.ws.cache.servlet.ServletWrapper.service
(ServletWrapper.java:259)
at com.ibm.ws.webcontainer.servlet.ServletWrapper.service
(ServletWrapper.java:1443)
at com.ibm.ws.webcontainer.servlet.ServletWrapper.service
(ServletWrapper.java:1384)
at com.ibm.ws.webcontainer.filter.WebAppFilterChain.doFilter
(WebAppFilterChain.java:131)
at pricequote.ARDThreadIdFilter.doFilter(ARDThreadIdFilter.java:40)
at com.ibm.ws.webcontainer.filter.FilterInstanceWrapper.doFilter
(FilterInstanceWrapper.java:184)


4. Java™ Servlet Specification Version 2.4 applications saw a performance degradation due to unoptimized functioning of the annotations scanner. This occured even if they were not configured to use annotations.

5. When ARD is run with Dynamic Caching enabled, there are intermittent ConcurrentModificationExceptions such as the following:


[9/16/08 16:50:46:160 CDT] 00000042 servlet E
com.ibm.ws.webcontainer.servlet.ServletWrapper service
SRVE0068E: Uncaught exception created in one of the service methods
of theservlet /AsyncRequestDispatcherJSPManual.jsp in application
ERWW_ARD_JSP_Client_05_21_2008. Exception created :
com.ibm.websphere.servlet.error.ServletErrorReport:
com.ibm.wsspi.ard.exception.ARDException: com.ibm.wsspi.ard.
exception.ARDException: java.util.ConcurrentModificationException
at org.apache.jasper.runtime.PageContextImpl.handlePageException
(PageContextImpl.java:693)
at com.ibm._jsp._AsyncRequestDispatcherJSPManual._jspService
(_AsyncRequestDispatcherJSPManual.java:114)
at com.ibm.ws.jsp.runtime.HttpJspBase.service(HttpJspBase.java:98)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:831)
at com.ibm.ws.cache.servlet.ServletWrapper.serviceProxied(ServletWrapper.java:307)
at com.ibm.ws.cache.servlet.CacheHook.handleFragment(CacheHook.java:574)
at com.ibm.ws.cache.servlet.CacheHook.handleServlet(CacheHook.java:250)
at com.ibm.ws.cache.servlet.ServletWrapper.service(ServletWrapper.java:259


6. Microsoft Internet Explorer Memory Leak analyzers showed a leak when using ARD client side aggregation. Eventually, the browser could come unresponsive after many requests.


7. When running the WebSphere Administrative Agent, some validation errors are seen in the administrative console.

The error was the following:

CHKW3630E: Load of platform features from
/wasv7config/bboadma/bboadma/AdminAgent/profiles/default/config/
cells/bbobase/bbonode/node-metadata.properties failed with exception
/wasv7config/bboadma/bboadma/AdminAgent/profiles/default/config/
cells/bbobase/bbonode/node-metadata.properties (EDC5129I No
such file or directory. (errno2=0x05620062)).


Full URI:
cells/bbobase/cell.xml

Validator classname:
com.ibm.websphere.validation.base.config.CellValidator

PROBLEM CONCLUSION:

1. The ARD Channel code was changed to fix the order of connection closing.

2. The URL for retrieving asynchronous include results was modified to be context root relative so that the proxy can determine where to route the request.

3. Request attributes required by dynacache were improperly being removed. The change prevents them from being removed.

4. Application server code was optimized to use a stubbed out annotation scanner for Java Servlet specification Version 2.4 applications.

5. ThreadLocal implementation was used to pass the information causing the concurrentModificationException.

6. Objects were properly de-referenced.

7. Correct directories paths were used to point to the missing properties file.

The fix for this APAR is currently targeted for inclusion in Fix Pack 7.0.0.1.
Please refer to the recommended updates page for delivery information:
http://www.ibm.com/support/docview.wss?rs=180&uid=swg27004980