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Re: idempotence of POST

From: Jeffrey Mogul <mogul@pa.dec.com>
Date: Thu, 19 Sep 96 10:50:00 MDT
Message-Id: <9609191750.AA18111@acetes.pa.dec.com>
To: Mike Meyer <mwm@contessa.phone.net>
Cc: http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
    I've always had a problem with the opposite problem - that GETS can be
    assumed to be safely reloadable.
    [...]
    So...
    
    > c) allow the return value of POST to indicate that the request
    >    can be repeated safely.
    > Is this worth pursuing?
    
    Yes, especially if the same mechanism is used to allow responses to
    GET requests indicate that they are NOT safely reloadable.

I think this would be dangerous.  HTTP/1.1 says that GETs are
assumed to be reloadable because this is, in fact, what most (all?)
existing caches assume, not necessarily because this is the best
way to have designed the original protocol.

If we were to add a mechanism to mark GET responses as non-reloadable,
it wouldn't do much good (at least, not for a long time) because
the server could never be sure that no older cache would get hold
of the response and ignore that mark.

-Jeff
Received on Thursday, 19 September 1996 11:03:14 EDT

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