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Question |
This technote documents the possible causes of an HTTP 503
(service unavailable) error as it relates to WebSphere® Application
Server. |
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Cause |
An HTTP status code 503 indicates that your Web server is
currently unable to handle the request because of a temporary overload or
maintenance of your server. However, as it relates to WebSphere
Application Server, this error indicates that your Web application is
unavailable for some reason. |
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Answer |
In all releases of V3.5, this error can occur for the
following reasons:
- Your Web application is disabled. Right-click the Web
application and verify that a check mark appears next to
enabled.
- A servlet that is configured to load at startup
fails to initialize, making the entire Web application unavailable. The
servlet can fail to initialize for three reasons:
- The servlet class is missing from your Web application
class path.
- The servlet init method fails.
- The servlet is marked disabled.
To check if a servlet is loading at startup, go to the Advanced
tab of the servlet. Then verify that your load at startup setting
shows true. Keep the WebSphere Application Server internal servlets
enabled to load at startup (for example: file serving servlet, JSP
processor, invoker, error reporter, and so forth). If the problem
described in reason "A" does not resolve the problem, set the load at
startup option to false. This action applies to any of your
custom built servlets. Restart your Web application and see if the
application is available.
In all releases of V4.0 and V5.0, this situation can occur for the
following reason:
A servlet that is configured to load at startup fails to initialize,
making the entire webModule unavailable. The servlet can fail to
initialize for three reasons:
- The servlet class is missing.
- The constructor of the servlet class fails with
exceptions. For example:
- NoClassDefFoundException
- ClassCastException
- The init method of the servlet fails.
To verify that your servlet is loading at startup, check your
web.xml file for that webModule:
<servlet id="Servlet_1">
<servlet-name>Controller Servlet</display-name>
<description>This is a controller
servlet</description>
<servlet-class>ControllerServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet> |
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Cross Reference information |
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