The point of looking at the cached headers is to see why the file was fetched more than once. The sort of things that might be seen are:
Different 'Expires' headers for recent dates
WWWOFFLE is re-fetching the page because the headers say that
the page has expired. You can stop WWWOFFLE doing this by
setting 'request-expired = no' in the OnlineOptions section of
the wwwoffle.conf file.
A 'Cache-Control: no-cache' or 'Pragma: no-cache' header
WWWOFFLE is re-fetching the page because it contains a header
that says that it is not to be cached. You can stop WWWOFFLE
doing this by setting 'reqeust-no-cache = no' in the
OnlineOptions section of the wwwoffle.conf file.
A 'Cache-Control: max-age=...' header and a 'Date' header
The specified age in seconds needs to be added to the date,
this sets an expiry time for the page and is treated the same
way as an 'Expires' header.
Different 'ETag' headers
WWWOFFLE is re-fetching the page because when it asks the
server if the page has changed (a different Etag) the server
says that it has (even though it may not have changed).
Disabling this will become an option in the next version of
WWWOFFLE.
The scripts are in this directory with examples of their use below.
$ ./find-duplicate-urls.sh
2 DikktDk-E6-RJzjBO0gLYTw http://images.slashdot.org/topics/topicgamesportable.gif ...
$ ./find-duplicate-headers.sh DikktDk-E6-RJzjBO0gLYTw
2 Accept-Ranges: bytes
2 Cache-Control: max-age=604800
2 Connection: close
2 Content-Length: 1278
2 Content-Type: image/gif
1 Date: Fri, 27 Jun 2003 05:16:13 GMT
1 Date: Sat, 28 Jun 2003 05:22:10 GMT
1 ETag: "1b408f-4fe-b7d3a080"
1 ETag: "2de1c-4fe-b7d3a080"
1 Expires: Fri, 04 Jul 2003 05:16:13 GMT
1 Expires: Sat, 05 Jul 2003 05:22:10 GMT
2 HTTP/1.1 200 OK
2 Last-Modified: Fri, 27 Jun 2003 03:41:38 GMT
2 Server: Apache/2.0.46 (Unix) mod_ssl/2.0.46 OpenSSL/0.9.6c
This has probably been refetched because of the Etag header.