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8.5.1: Plug-in problems

8.5.1: Plug-in problems

HTTP servers are legacy Web products, created at a time when they were the only conduit between browsers and HTML or CGI files. With the evolution of Web technology, users now require servers to handle servlets, JSP files and EJBs. WebSphere Application Server supports this technology, but to provide these functions it must intercept requests sent to the HTTP Server.

The plug-in component extends the function of the HTTP Server by intercepting requests and passing them to either WebSphere Application Server or the HTTP Server. The following three files in the <WAS_root>temp directory allow the plug-in to determine the request's destination:

  • <WAS_root>/temp/rules.props
    • Provides a snapshot of the existing topology and lists available Web resources and paths to handle service requests
  • <WAS_root>/temp/vhosts.props
    • Provides virtual hosting information that is transferred to the WebSphere Application Server runtime environment
  • <WAS_root>/temp/queues.props
    • Provides names of links to different servlet engines. The number of links listed in this file vary according to the number of application servers, clones and other servlet engine resources that are defined in the product.

    This is the high level view of the plug-in process flow:

    Browser -->  WebSphere plugin -->  HTTP Server or WebSphere Application Server
    

    Typical plug-in problems

    Generally, plug-in failures are caused by missing files or an incorrectly configured HTTP Server.

    To diagnose plug-in problems, verify the data in the files are consistent with both the HTTP request and the active configuration in the servlet engine. The plug-in configuration files are generated periodically so a delay can occur between the time a change is made in the system and the time the change is reflected in the configuration files.

    The following error descriptions are symptoms of plug-in problems:

    1. Servlet requests are not fulfilled. Verify the following to determine the cause of the problem:
      • The Web server can serve HTML pages
      • The administrative console can connect to the Web server
      • The Default server is started
      • Ensure the Web server hostname and port number are identical to the ones defined in the virtual host's alias table.
      • Ensure the appropriate .DLL file for the Web server is present in the <WebSphere-root>bin
    2. Pipe broken messages appear. Verify the following to determine the cause of the problem:
      • TCP/IP connection exists between Web server and WebSphere Application Server.
      • No process or thread failures occurred.
      • No access violations occurred.

    How to debug plug-in problems

    Check for errors in the following logs, and in the trace file:

    • trace.log.<http server>.<date>
    • <AppServer>_stderr.log
    • <AppServer>_stdout.log
    • <AppServer>_native.log.<date>
    See files 8.3: Logs and 8.4: Trace for more information on logs and trace file.

    If there are no entries in the logs or trace file, comment out the WebSphere Application Server plugin in the httpd.conf file. This will help you determine if the failure originates with WebSphere Application Server or the HTTP Server.

    The WebSphere plugin property in the httpd.conf file is:

    Load Module ibm_app_server_module

    Restart the HTTP Server. If the Web Server initializes and runs, then WebSphere Application Server has a problem.


Go to previous article: Identifying the Problem Go to next article: Servlet Redirector Problems

 

 
Go to previous article: Identifying the Problem Go to next article: Servlet Redirector Problems