Network Deployment (Distributed operating systems), v8.0 > Reference > Troubleshoot tips

HTTP session problems

1. Overview
2. HTTP sessions are not getting created, or are lost between requests
3. HTTP Sessions are not persistent
4. Session is shared across multiple browsers on same client machine
5. Session is not getting invalidated immediately after specified session timeout interval
6. Unwanted sessions are being created by JSP
7. Session data intended for one client is seen by another client
8. Users are not logged out after the HTTP session timer expires
9. Runtime exceptions when updating applications where session persistence is enabled

Overview

To view session manager settings...

Application server | Additional properties | Web Container | Session manager

If your problem is not described here, or none of these steps fixes the problem:

• Review HTTP session manager troubleshooting tips for general steps on debugging session-manager related problems.

• Review Task overview: Managing HTTP sessions for information on how to configure the session manager, and best practices for using it.

• Check to see if the problem has been identified and documented by looking at the available online support (hints and tips, technotes, and fixes).

• If you don't find your problem listed there contact IBM support.

HTTP sessions are not getting created, or are lost between requests

By default, the session manager uses cookies to store the session ID on the client between requests. Unless you intend to avoid cookie-based session tracking, ensure that cookies are flowing between WAS and the browser:

• Make sure the Enable cookies check box is checked under the Session tracking Mechanism property.

• Make sure cookies are enabled on the browser you are testing from or from which your users are accessing the application.

• Check the Cookie domain specified on the SessionManager (to view the or update the cookie settings, in the Session tracking mechanism > enable cookies property , click Modify).

  • For example, if the cookie domain is set as ".myCom.com", resources should be accessed using that domain name. Example: http://www.myCom.com/myapp/servlet/sessionservlet.

  • If the domain property is set, make sure it begins with a dot (.). Certain versions of Netscape do not accept cookies if domain name doesn't start with a dot. Internet Explorer honors the domain with or without a dot. For example, if the domain name is set to mycom.com, change it to .mycom.com so that both Netscape and Internet Explorer honor the cookie.

    When the servers are on different hosts, ensure that session cookies flow to all the servers by configuring a front-end router such as a web server with the plug-in or setting the Cookie domain.

• Check the Cookie path specified on the SessionManager. Check whether the problem URL is hierarchically below the Cookie path specified. If not correct the Cookie path.

• If the Cookie maximum age property is set, ensure that the client (browser) machine's date and time is the same as the server's, including the time zone. If the client and the server time difference is over the "Cookie maximum age" then every access would be a new session, since the cookie expires after the access.

• If we have multiple web modules within an enterprise application that track sessions:

  • To have different session settings among web modules in an enterprise application, ensure that each web module specifies a different cookie name or path, or

  • If web modules within an enterprise application use a common cookie name and path, ensure that the HTTP session settings, such as Cookie maximum age, are the same for all web modules. Otherwise cookie behavior is unpredictable, and depends upon which application creates the session. Note that this does not affect session data, which is maintained separately by the web module.

• Check the cookie flow between browser and server:

  1. On the browser, enable "cookie prompt". Hit the servlet and make sure cookie is being prompted.

  2. On the server, enable SessionManager trace. Enable tracing for the HTTP session manager component, by using the trace specification "com.ibm.ws.session.*=all=enabled". After trace is enabled, exercise your session-using servlet or JSP, then follow the instructions for dumping and browsing the trace output .

  3. Access the session servlet from the browser.

  4. The browser prompts for the cookie; note the jsessionid.

  5. Reload the servlet, note down the cookie if a new cookie is sent.

  6. Check the session trace and look for the session ID and trace the request by the thread. Verify that the session is stable across web requests:
     • Look for getIHttpsession(...) which is start of session request.
     • Look for releaseSession(..) which is end of servlet request.

• If you are using URL rewriting instead of cookies:

  • Ensure there are no static HTML pages on the application's navigation path.

  • Ensure that your servlets and JSP files are implementing URL rewriting correctly. For details and an example see Session tracking options.

• Deprecated feature: Session tracking using the SSL ID is deprecated in WAS v7. We can configure session tracking to use cookies or modify the application to use URL rewriting.depfeat If you are using SSL as your session tracking mechanism:

  • Ensure that we have SSL enabled on your IBM HTTP Server or iPlanet HTTP server.

  • Review Session tracking options.

• If you are in a clustered (multiple node) environment, ensure that we have session persistence enabled.

HTTP Sessions are not persistent

If your HTTP sessions are not persistent, that is session data is lost when the application server restarts or is not shared across the cluster:

• Check the data source.

• Check the session manager's persistence settings properties:

  • If you intend to take advantage of session persistence, verify that Persistence is set to Database.

  • Persistence could also be set to Memory-to-Memory Replication.

  • If you are using Database-based persistence:

    • Check the JNDI name of the data source specified correctly on SessionManager.

    • Specify correct userid and password for accessing the database.

      Note that these settings have to be checked against the properties of an existing data source in the admin console. The session manager does not automatically create a session database for you.

    • The data source should be non-JTA, for example, non XA enabled.

    • Check the JVM logs for appropriate database error messages.

    • With DB2, for row sizes other than 4k make sure specified row size matches the DB2 page size. Make sure tablespace name is specified correctly.

  • If you are using memory-based persistence (available only in a network deployment environment):

    • Review Memory-to-memory replication.

    • Review the Internal Replication Domains properties of your session manager.

Session is shared across multiple browsers on same client machine

This behavior is browser-dependent. It varies between browser vendors, and also may change according to whether a browser is launched as a new process or as a subprocess of an existing browser session (for example by hitting Ctl-N on Windows).

The Cookie maximum age property of the session manager also affects this behavior, if cookies are used as the session-tracking mechanism. If the maximum age is set to some positive value, all browser instances share the cookies, which are persisted to file on the client for the specified maximum age time.

Session is not getting invalidated immediately after specified session timeout interval

The SessionManager invalidation process thread runs every x seconds to invalidate any invalid sessions, where x is determined based on the session timeout interval specified in the session manager properties. For the default value of 30 minutes , x is around 300 seconds. In this case, it could take up to 5 minutes (300 seconds) beyond the timeout threshold of 30 minutes for a particular session to become invalidated.

Unwanted sessions are being created by JSP

As required by the JSP specification, JSP pages by default perform a request.getSession(true), so that a session is created if none exists for the client.

To prevent JSP pages from creating a new session, set the session scope to false in the .jsp file using the page directive as follows:

<% @page session="false" %> 

Session data intended for one client is seen by another client

In rare situations, usually due to application errors, session data intended for one client might be seen by another client. This situation is referred to as session data crossover. When the DebugSessionCrossover custom property is set to true, code is enabled to detect and log instances of session data crossover. Checks are performed to verify that only the session associated with the request is accessed or referenced. Messages are logged if any discrepancies are detected. These messages provide a starting point for debugging this problem. This additional checking is only performed when running on the WebSphere-managed dispatch thread, not on any user-created threads.

For additional information on how to set this property, see article, Web container custom properties.

Users are not logged out after the HTTP session timer expires

If users of WAS log onto an application and sit idle longer than the specified HTTP session timeout value, the user information is not invalidated and user credentials stay active until LTPA token timeout occurs.

After you apply PK25740, complete the following steps to log out users from the application after the HTTP session has expired.

1. In the admin console, click...
   Security | Global security | Custom properties | New

2. In the Name field, enter...
   com.ibm.ws.security.web.logoutOnHTTPSessionExpire

3. In the Values field, enter true.

4. Click Apply and Save to save the changes to the configuration.
5. Resynchronize and restart the server.

Unexpected re-authentications: When you set the com.ibm.ws.security.web.logoutOnHTTPSessionExpire custom property to true, unexpected re-authentications might occur when you are working with multiple web applications. By default, each web application has its own unique HTTP session, but the web browser has one session cookie.

To address this issue, you can change the HTTP session configuration by giving each application a unique session cookie name or path setting. As a result, each application gets its own session cookie. Alternatively, you can configure multiple web applications with the same enterprise application to share the same HTTP session. For more information, see the Assembling so that session data can be shared topic.

Run time exceptions when updating applications where session persistence is enabled

Users who have session persistence enabled and execute application updates during run time might experience unexpected exceptions after the application is restarted.

If updates have been made that change the attributes saved, then all the sessions created by the associated application might have to be invalidated prior to the application update if the application can not handle these changes. In this situation, all session objects must be removed from the back-end as well. See the HTTP session invalidation information to learn more about how to remove these sessions properly.

IBM Support has documents and tools that can save you time gathering information needed to resolve problems as described in Troubleshoot help from IBM. Before opening a problem report, see the Support page:

• http://www.ibm.com/software/webservers/appserv/was/support/

Best practices for using HTTP sessions
Sessions
HTTP session invalidation
Task overview: Managing HTTP sessions
HTTP session manager troubleshooting tips
Assembling so that session data can be shared

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