Attachment updates sometimes invisible

I've repeatedly had a problem in which after I upload a new attachment I still see the old one, even though the new one is definitely there (as witnessed when using a different browser or machine to view the page). This appears to be a caching problem. Sometimes I've experienced the problem even when using a second browser, suggesting some intermediate cache is involved. Also, admins local to the site have not been able to duplicate the problem. I also have not seen the problem using this site. The attachment is javascript code used by the page to which it is attached. The code that runs is the old code when this happens.

I have not seen it on this site (http://foswiki.org/Sandbox/RBAttachTest), but have seen it, sometimes, at the site I am attempting to update (http://ctspedia.org/do/view/Sandbox/RBAttachTest). That site runs an older version of the software.

I looked at the http headers associated with retrieving the attachment; it doesn't look as if any cache-related options (e.g., don't cache) are set.

Here are the exact steps I followed while testing:
* enter ctspedia.org in location bar
* click log in at top of right hand box
* enter name and password
* click sandbox in the right hand box under "Special Resources"
* under "create a new document by name" enter RBATTACHTest2 and
click on "Create by Name"
* I am now in a WYSWIG editor. Position before signature line, hit
enter, move up to blank line and type "test page for attachments"
and hit "save" button under edit area.
* click on the "Attach" option of the "toolbar" under the page.
* click on browse for Attach a new file. Go to this file, which is
called attachecache.txt.
* enter comment "attached file"
* click blue "upload file" button.
* I'm not back at the main page. Click on the blue triangle on the
* "attachments" button directly under my signature line.
* In the resulting table, in the 2nd column (labelled "Attachment")
click on the file name attachcache.txt.
* This file displays.
* Hit the back arrow.
* in the attachment table, click the "manage" link for this file.
* edit and save a new version of this file
* again click browse and select this file again.
* click the blue upload file button at the bottom.
* now back in the attachment table, click the file name.
* I see the old version of the file<<<<
* If I open Firefox and go to the same page, I also see the old
version. That's a surprise.
* Connect remotely to home and use lynx to go to page without logging
in. I also see the old version.
* edit and save a new version of this file
* in the attachment table, click the "manage" link for this file.
* again click browse and select this file again.
* click the blue upload file button at the bottom.
* now back in the attachment table, click the file name. This time I
see the new version!

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All I can guess is that this is something to do with caches - either in your web server, or in your browser. Try clearing both, and you should see the latest upload.

-- CrawfordCurrie - 06 Feb 2012