[Webkit-unassigned] [Bug 37784] New: Webkit revalidates resources despite max-age Cache-Control headers and Expires headers in their responses

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=37784

           Summary: Webkit revalidates resources despite max-age
                    Cache-Control headers and Expires headers in their
                    responses
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Macintosh Intel
               URL: http://www.google.com/images?q=webkit
        OS/Version: Mac OS X 10.6
            Status: UNCONFIRMED
          Severity: Normal
          Priority: P2
         Component: New Bugs
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: roberteperrin at gmail.com


Steps to Reproduce
Load the page at http://www.google.com/images?q=webkit.
Note via the inspector that the images in the search results are all returned
with http Cache-Control headers reading "public, max-age=31536000", and Expires
headers about a year in the future.
Select the url bar and hit return to load the page again.

Actual Results
The search result images are all reverified on the server via conditional GETs
with Cache-Control headers reading "max-age=0" and If-Modified-Since headers
holding dates a couple of months in the past.

Expected Results
The max-age headers are respected and the search result images are loaded from
cache, with no request (conditional or not) sent to the server.

Build Date & Platform:
Safari 4.0.5 and recent Webkit nightlies (6531.22.7, r57720) on MacOS X 10.6.3,
and the current stable version of Chrome on Windows 7 all display this
behavior.
Firefox on Mac appears to respect the max-age header, and trusts it's cached
data instead of making any requests to the sever for the search result images
on subsequent page loads.

Additional Information:
While the data transferred is negligible, the latency delays incurred by these
requests may be significant.  
The delays may be especially significant if the page is being loaded over an
inherently high-latency mobile connection, or if the page being loaded has
enough subresources being revalidated that the web browser uses up all of it's
(6?) available connections and needs to wait for responses to begin loading
other subresources, or if the web server responsible for the subresources being
revalidated is especially slow due to the "max-age=0" Cache-Control header in
webkit's conditional GET request bypassing it's fast path for delivering cached
responses.

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