ISAPI/GWAPI Application Brokers

Two additional versions of the Application Broker have been developed for heavily loaded systems where performance is critical. These versions are built as shared libraries that are linked directly into the Web server at run time. When a new request is accepted by the Web server, it starts an Application Broker copy in a Web server thread rather than starting a new CGI process. In this manner, the overhead of process creation is replaced by the creation of a new Web server thread.

The two new modules are broker.dll (ISAPI Windows) and broker.so (GWAPI z/OS). These files are typically installed into the Web server CGI directory. When the first request is made to the Web server, these modules are loaded and linked to the Web server. The Application Broker configuration file is read once and stored in memory. This means that if the configuration file is subsequently changed, the Web server must be stopped and restarted in order to reload the changes. On Windows, the IIS Admin Service must also be stopped and restarted, using the Control Panel Services dialog box. To see when the configuration file was last read, invoke the Application Broker with a _DEBUG value of 16384.

To use the ISAPI version on Windows, change the URL in the Web browser from broker.exe to broker.dll. A URL of the form

http://yourserver/cgi-bin/broker.dll?

loads and executes the ISAPI module. If no parameters are specified, then the default or optional customized welcome page is displayed.

ISAPICacheFile c:/cgi-bin/broker.dll
Addhandler isapi-isa .dll

You must also add the ExecCGI options line to the directory section of the HTTPD.CONF file, as follows:

<Directory "C:/Program Files/Apache Group/Apache2/cgi-bin">
   AllowOverride None
   Options ExecCGI
   Order allow,deny
   Allow from all
</Directory>

For ISAPI, the Application Broker thread typically runs under the user ID IUSR_nodename, as it does with the CGI version.

The z/OS GWAPI version requires a Web server configuration change. Add a line of the form

Service /cgi-bin/gwbroker* /dept/test/cgi-bin/broker.so:broker

to the Web server configuration file httpd.conf. In addition, execute the following command for the broker.so module:

extattr +p /dept/test/cgi-bin/broker.so

The exact form of the commands depends on the directory specification for the CGI directory. Changing the URL to the form

http://yourserver/cgi-bin/gwbroker?

loads and executes the GWAPI module, which looks for an Application Broker configuration file named gwbroker.cfg. If no parameters are specified, then the default or optional customized welcome page (gwbroker.html) is displayed.

For GWAPI, the Application Broker runs under the same user ID as the Web server.