Re: [Tzdist] tzdist examples

[Lester Caine <[e-mail]>]

On 11/01/15 20:46, Paul Eggert wrote:
> Lester Caine wrote:
>> There is no need
>> for every user to have to download a complete set of data just because
>> one server has become inaccessible - perhaps temporarily.
> 
> Sure, and that's true regardless of whether list actions use
> changedsince=ETag or changedsince=timestamp.  If multiple redundant
> servers are well managed, they should agree about ETag values, just as
> they should agree about timestamps.
> 
>> If version is part of the ETag element, then that mechanism can be used
>> as a part of the process.
> 
> That'd be one way to implement ETag values, but I'm leery of requiring
> this in the standard.  It'd be more fruitful to think of tzdist as
> something that at least in principle could be implemented atop standard
> caches like Squid and standard web servers like Apache.

I don't see any problem - as far as I am aware as long as the hash
returned via ETag for the same data package is the same for each server
then there is no problem, and certainly standard cache methods allow
that to happen? It is only that the accessing URL needs to provide the
current version in order to know that the server now has a new version
to provide, and more important if a server has not been updated an error
is provided if the replacement server does not actually understand the
version being requested.

The race problem may result in more than one version being propagated at
any time and this must not disrupt the process.

-- 
Lester Caine - G8HFL
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