[Webkit-unassigned] [Bug 29182] New: AppCache re-fetches the host page when the host page is not cached by the browser's main cache

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Fri Sep 11 07:56:51 PDT 2009


           Summary: AppCache re-fetches the host page when the host page
                    is not cached by the browser's main cache
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: All
        OS/Version: All
            Status: UNCONFIRMED
          Severity: Minor
          Priority: P3
         Component: New Bugs
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: agrieve at google.com
                CC: agrieve at google.com

A summary of what happens when first visiting an page with a manifest is as

1. Fetch the page
2. Fetch the manifest
3. Fetch resources on the page
4. Fetch all resources in the manifest

The host page is *always* a resource in the application cache, since even if
it's not listed, it is added as in implicit entry. In step 4, it re-fetches the
host page to put into the Application Cache, even though it has just been
fetched. This is not so bad in the case where the host page was put into the
browser's normal cache. However, if the page is served with no-cache headers,
or if it is too big to be put into the normal cache (as is often the case on
the iPhone), then the host page is fetched over the network for a second time.

The problem case should be optimized by having AppCache not fetch the host page
over the network. Instead, the host page (and any other resources linked from
it that are also listed in the manifest) should be put into AppCache as soon as
they are downloaded the first time.

To test this behaviour, create a simple page that has an empty manifest and
serve it with Cache-Control: no-cache and then watch what requests are made
during page load.

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