W3C home > Mailing lists > Public > public-html-bugzilla@w3.org > January 2011

[Bug 11895] Make Downloads more reliable by specifying checksums

From: <bugzilla@jessica.w3.org>
Date: Sun, 30 Jan 2011 00:13:36 +0000
To: public-html-bugzilla@w3.org
Message-Id: <E1PjKvA-0007Gn-9y@jessica.w3.org>

--- Comment #7 from Aryeh Gregor <Simetrical+w3cbug@gmail.com> 2011-01-30 00:13:35 UTC ---
(In reply to comment #5)
> Unfortunately, nothing will help if you (I presume the publisher) upload the
> wrong file.  This proposed solution will only make all downloads show up as
> failed.

Which is correct, since they're all corrupted.  Presumably users would complain
in this case and the publisher could fix it, rather than all users just
silently getting corrupted files.

> Apache's httpd documentation states that the message digest is calculated upon
> each request, placing a burden on the web server.  In fact, they seem to
> recommend *against* using this feature by saying:
> "Note that this can cause performance problems on your server since the message
> digest is computed on every request (the values are not cached)."

This is just because nobody actually has any use for the feature, so nobody's
bothered optimizing it.  It's not a necessary problem.  In particular, if
downloads are served by a web application instead of by the web server
directly, it would be pretty trivial to have the web app compute the hash once
at upload time and serve the header.  Commonly you want some kind of user
application to serve the file anyway to handle permissions or store download
statistics; the performance impact can be negligible if you use X-Sendfile or

But a solution in HTML seems more useful anyway, for the reasons I gave.

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Received on Sunday, 30 January 2011 00:13:39 UTC

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