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Re: [Tzdist] Fwd: [tzdist] #32 (service): managing historical data

Tim Parenti <tim@timtimeonline.com> Wed, 10 December 2014 17:32 UTC

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Date: Wed, 10 Dec 2014 12:32:47 -0500
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From: Tim Parenti <tim@timtimeonline.com>
To: Lester Caine <lester@lsces.co.uk>
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Cc: Time Zone Data Distribution Service <tzdist@ietf.org>
Subject: Re: [Tzdist] Fwd: [tzdist] #32 (service): managing historical data
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On 10 December 2014 at 12:26, Lester Caine <lester@lsces.co.uk> wrote:

> This STILL misses the race hazard that exists with CURRENT data! First
> it assumes that everybody s using the one published set of data. That
> has been thrown out, so several sets will exist.
>

If some sort of identifier for the version is packaged with the response —
and I believe this is the intent of "changedsince" — then I don't see the
hazard.  If a particular publisher is slow to fetch and distribute
newly-available data, the old data they distribute will still be tagged as
such and obsoleted as normal once the updates become available from that
publisher.

Where I *do* see a potential race hazard is in defining exactly what value
"changedsince" takes on.  Is it the time at which a tzdist publisher
receives the new data, or begins distributing it, even if it was
technically available to them hours or days beforehand?  Or should this
date be fixed at the source (e.g., tz release timestamps) and propagate
somehow throughout the tzdist system?

--
Tim Parenti

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