ISAPI programming documentation

ISAPI is a high-performance C-based API in Zeus Web Server. The following documentation gives
a quick overview, and function reference for the API.

The ISAPI module is responsible for loading and running ISAPI filters and extensions. ISAPI provides a vendor-independent way of extending the functionality of your web server. It offers far more flexibility than the CGI interface and avoids all the performance limitations. Within the Zeus Web Server, you can choose to run both filters and extensions as "in-process" or "out-of-process". "in-process" means that filters or extensions run in the same process space as the virtual-server, while "out-of-process" means that these run in a separate process, independent from the server.

You should note that "in-process" ISAPI could affect the stability and/or performance of your virtual-server (as "in-process" ISAPI filters and extensions run in the same process space as the virtual-server), if you are running a filter or extension that has very high latency (I/O intensive or with long processing cycles) "in-process", that means that the virtual- server will be unable to process further requests until the ISAPI module is done processing. In this case the ideal situation is to run it "out-of-process". Other factors to consider are the stability/security of the filters and extensions you are running. If these prove to be unreliable or unsecure, the integrity of the virtual-server could be compromised, if you run these as "out-of-process" the only affected component of the web server would be the ISAPI runner, not the parent virtual-server processes.

Some examples of common choices are depicted in the following table:

Reference

• Introduction to ISAPI
• Reference guide
• Programming considerations when using the "out-of-process" model.
• Example code which rewrites URL requests on-the-fly
• More sophisticated example code mapping URL requests to home directories

Content Manager [Administrator] 16 December 2005