R – IIS 7 static file compression problem

compressioniis-7

We have 3 web servers running IIS7. I've enabled compression for static and dynamic content. We have been testing the servers under heavy load and after half an hour the styles on the site started breaking.

I started investigating and found out that IIS was serving css and js files with Content-Encoding: gzip but the actual file content is not compressed. This cause the browsers to give error when trying to process the content. The issue disappears if I restart IIS.

Have anyone experienced a similar issues? What is the best way to diagnose the issue?

Thanks

Best Answer

The problem was caused by the CMS (sitecore) we were using. We upgraded to a later version and it has worked ever since. It's probably a 3rd party httpmodule causing the issue.

UPDATE: Browsers have been dropping support for raw deflate. zOompf has completed some very thorough research on this very topic here. Unfortunately, it appears that raw deflate is NOT safe to use.

~~Check http://www.vervestudios.co/projects/compression-tests/results for more results.~~

~~Here are the browsers that have been tested:~~

/* Browser DEFLATE ZLIB */ XP Internet Explorer 6 PASS FAIL XP Internet Explorer 7 PASS FAIL XP Internet Explorer 8 PASS FAIL Vista Internet Explorer 8 PASS FAIL XP Firefox 3.6.* PASS PASS XP Firefox 3.5.3 PASS PASS XP Firefox 3.0.14 PASS PASS Win 7 Firefox 3.6.* PASS PASS Vista Firefox 3.6.* PASS PASS Vista Firefox 3.5.3 PASS PASS XP Safari 3 PASS PASS XP Safari 4 PASS PASS XP Chrome 3.0.195.27 PASS PASS XP Opera 9 PASS PASS XP Opera 10 PASS PASS XP Sea Monkey 1.1.8 PASS PASS Android 1.6 Browser (v4)* N/A N/A OS-X Safari 4 PASS PASS OS X Chrome 7.0.517.44 PASS PASS OS X Opera 10.63 PASS PASS iPhone 3.1 Safari PASS PASS

* Android Sends HTTP request header "Accept-Encoding: gzip". Deflate is not permitted.

I conclude that we can always send raw DEFLATE (when the HTTP request header "Accept-Encoding" contains "deflate") and the browser will be able to correctly interpret the encoded data. Can someone prove this wrong?

~~note: .NET's native implementation of DEFLATE (System.IO.Compression.DeflateStream) is raw DEFLATE. It also sucks. Please use zlib.net for all of your .NET deflating needs.~~

Json – How to compress a Json result from ASP.NET MVC with IIS 7.5

Make sure your %WinDir%\System32\inetsrv\config\applicationHost.config contains these:

<system.webServer>
    <urlCompression doDynamicCompression="true" />
    <httpCompression>
      <dynamicTypes>
        <add mimeType="application/json" enabled="true" />
        <add mimeType="application/json; charset=utf-8" enabled="true" />       
      </dynamicTypes>
    </httpCompression>
</system.webServer>

From the link of @AtanasKorchev.

As @simon_weaver said in the comments, you might be editing the wrong file with a 32 bit editor on a 64 bit Windows, use notepad.exe to make sure this file is indeed modified.

Best Answer

Related Solutions

Deflate compression browser compatibility and advantages over GZIP

UPDATE: Browsers have been dropping support for raw deflate. zOompf has completed some very thorough research on this very topic here. Unfortunately, it appears that raw deflate is NOT safe to use.

Json – How to compress a Json result from ASP.NET MVC with IIS 7.5

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