IIS 7.5 and ARR - 304 status code not sent for images

Question

We have setup a reverse proxy using ARR in front of our Sitecore site. We are using this reverse proxy for serving sitecore media items only. Sitecore media items are getting cached properly on disk using ARR.

Now the problem we are facing is that, for all images, the HTTP Status Code is always 200 and so they are not cached in browser. If we disable reverse proxy then HTTP Status Code is 304 and browser renders images from local cache.

Is there any reason why ARR does not send 304 status code ?

Update #1: Below is the ARR rule which we have setup:

    <rule name="Default ReWrite" enabled="true" patternSyntax="ECMAScript" stopProcessing="true">
      <match url="^(.*)" />
      <conditions>
                    <add input="{CACHE_URL}" pattern="^(https?)://" />
      </conditions>
      <action type="Rewrite" url="http://127.0.0.1/{R:0}" logRewrittenUrl="true" />
                <serverVariables>
                </serverVariables>
    </rule>

What is the value of the `MediaResponse.Cacheability` setting in your web.config? And what version of Sitecore are you running? — computerjules, Jun 24 '14 at 16:45
@computerjules, I'm using Sitecore 6.6 and the MediaResponse.Cacheability setting is set as "public". — nishantagarwal, Jun 24 '14 at 18:22
That setting is fine. Can you provide the settings of the ARR rule you have defined? — computerjules, Jun 24 '14 at 19:00
@computerjules, do you mean in IIS 8.5, ARR returns 304 status code for cached media files ? — nishantagarwal, Jun 25 '14 at 06:21
Try specifying exact file extensions like *.jpg, *.gif and see if that makes a difference. Worth a shot. — Brock Hensley, Jun 26 '14 at 03:17
Could it be that the empty serverVariables element is removing all headers including the If-Modified-Since that the browser sends to ARR? — pbering, Jun 26 '14 at 19:51
@nishantagarwal, You should remove the element completely, it should only be there if you need to add or rewrite server variables — pbering, Jun 26 '14 at 20:04
@pbering, I removed serverVariables element, but still it did not work. — nishantagarwal, Jun 27 '14 at 06:23

score 3 · Accepted Answer · answered Jun 26 '14 at 21:22

3

See the post: http://forums.iis.net/t/1213330.aspx?ARR+Disk+cache+return+200+instead+of+304+for+cached+files

Looks like its related to ETAG (IF-NONE-MATCH) headers - this wont work if the ETAG is issued from a server and later gets validated by another server (ARR in this case). So ARR never returns 304 to browser, but simply gets the cached file from disk and returns 200 to browser.

answered Jun 26 '14 at 21:22

Yasin75

56
2

thanks for this suggestion. After removing the ETAG, ARR started sending 304 status code for cached files. – nishantagarwal Jun 27 '14 at 06:43
FYI, to remove ETAGs from response in IIS, an outbound rule can be used. Check below SO post for more details: http://stackoverflow.com/a/18025228/1101223 – nishantagarwal Jun 27 '14 at 06:43

IIS 7.5 and ARR - 304 status code not sent for images

1 Answers1