Does the output cache respect response headers?

Question

I'm considering using the ASP.NET output cache to improve the performance of my custom HTTP handler.

If I set an expiry header in the response, will the output cache be intelligent enough to cache the response accordingly? Or do I need to manually create an appropriate CacheDependency?

If I gzip the response and set the Content-Encoding header, will the output cache be smart enough to prevent the response being double-gzipped if dynamic compression is turned on? What happens if the output cache has a gzipped version and a client that doesn't accept gzip requests the resource?

Answer 1

You can set the output cache to cache content relative to accept headers, not response headers. From this walkthrough on IIS 7.0 caching:

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
  <system.webServer>
    <directoryBrowse enabled="true" />
        <caching>
            <profiles>
                <add extension=".jpg" policy="CacheForTimePeriod"
                duration="00:00:10" varyByHeaders="Accept-Language" />
            </profiles>
        </caching>                  
  </system.webServer>
</configuration>

Using this configuration, the output cache will cache a different value for each language that user agent's ask for. You could add "Accept-Encoding" to the varyByHeaders to cache gzipped and non-gzipped versions of the same resource.

As for expiry headers, as far as I can tell the output cache doesn't take any notice of them. You have to set the output cache expiry and the expiry HTTP header seperately - after all there's no guarantee that you would want to use the same policy for both.