Archives
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IIS 7 C++ Module API Sample: Controlling http.sys caching
In my previous post we saw that http.sys caching can be very useful for high traffic (gigabits/sec) sites. In this post we create a sample module that allows configuring which URLs can enter the cache.
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Fun with http.sys Caching
There are many caches available to web applications. Today I will play with the http.sys URI cache. It is a simple, fast, kernel-mode cache.
How it Works
First IIS must decide if the response can be stored in the http.sys' cache (devs: See HttpSendHttpResponse's pCachePolicy argument). There are about twenty reasons for IIS to decide something should not get in the cache (because of the cache's simple design). To find out why a specific request is not being cached, enable "Failed Request Tracing" and look for the HTTPSYS_CACHEABLE event's reason field.