Subject: Re: Our old friends, weak ETags

From: Bruce Perens <[email-masked]>
Date: Fri, 20 Jul 2012 05:08:18 +0000

Hi Adrien,

I use ETag because of an insufficiency in RFC 2616 dates: their 
resolution is one second. Updates to entities at sub-second intervals 
are possible and would result in entities with the same Last-Modified 
date. To be pedantically resolution-independent, I convert the date/time 
to a string representation of a ratio. It's presently the number of 
nanoseconds since the epoch. I encode that and an entity serial number 
in the ETag.

If HTTP dates are extended to have sub-second resolution, I will 
probably be able to do without ETags.

     Thanks

     Bruce

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From: Julian Reschke <[email-masked]>
Date: Fri, 20 Jul 2012 09:55:21 +0200

> probably be able to do without ETags.

That explains the choice of ETags, but not necessarily *weak* ETags.

(I think Apache httpd uses weak etags if it can't get a sub-second 
timestamp from the file system)

Best regards, Julian