SendRedirect problem with Dispatcher and Websphere

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Laatst bijgewerkt op 3 mei 2021 | Ook van toepassing op Dispatcher

Problem, Question

Following setup: IHS Webserver with Dispatcher module configured which in turn points to a Websphere app-server render farm where a CQ instance is running. A class or jsp script in CQ calls the response.sendRedirect() method which results in a wrong redirect: the internal server name and port of the Websphere app-server which is not reachible from the outside is exposed in the Location response header which is used to do the actual redirect.

The root cause of this problem is Websphere itself as IBM's implementation of the HttpServletResponse#sendRedirect() method is directly influenced by custom request headers, per default generated by Websphere's IHS plugin. This is considered as an IBM vendor lock-in issue.

Resolution, Answer

Using mod_headers in the IHS webserver it is possible to pass Websphere specific headers to the app-server by adding such headers with the RequestHeader directive. In addition to that, these custom headers need to be explicitely allowed in the Dispatcher configuration, otherwise these custom headers will be ignored.

Example:

public domain: http://www.mydomain.com

IHS configuration

Edit the httpd.conf configuration file of the IHS webserver and do the following:

make sure that the module mod_headers is present and loaded
add WAS specific headers using RequestHeader directive

Example (excerpt from httpd.conf):

...
LoadModule headers_module modules/mod_headers.so
...
<Directory />
    <IfModule disp_apache2.c>
        # set custom Websphere headers
        RequestHeader set $WSSN www.mydomain.com
        RequestHeader set $WSSP 80
  
        SetHandler dispatcher-handler
    </IfModule>
    Options FollowSymLinks
</Directory>

Dispatcher configuration

On Dispatcher level, it is required to add the list of above configured request headers to the list of client headers that the Dispatcher will forward to the defined render farm, Websphere app-server in this case.

Please do the following:

edit the dispatcher.any configuration file
locate the section /clientheaders and add additional headers to be included
restart IHS

Example (excerpt from dispatcher.any):

...
  /clientheaders
    {
    ...
    "$WSSN"
    "$WSSP"
    }
...

Websphere configuration

The $WSSP Websphere header specifies the port and $WSSN defines the hostname to be used when response.sendRedirect() is called in Websphere. In addition to that, the port provided in the $WSSP header is also used to map the virtual host in Websphere.

Connect to the Administration Console of Websphere and do the following:

browse to Environment > Virtual Hosts
select the virtual host configuration which is used for CQ
click on Host Aliases
add port 80
restart Websphere if required

NOTE: it might be required to add more Websphere specific headers, depending on the setup. Please refer to this document describing Websphere specific headers and their meaning.