Subject: Idempotency in EPP

From: Robert Burbidge <[email-masked]>
Date: Thu, 27 Jun 2002 15:11:56 +0100

Can I just get confirmation of a small point regarding idempotency?

My understanding of idempotency is that if the server received two identical
commands from a registrar then it should produce the same results for each
identical command. This is to ensure, for example, that if the server is
hanging off a session-less protocol that cannot guarantee unique delivery of
datagrams it's OK to action the same command twice. There seems to be two
aspects to this - that both commands have the same effect, and that both
commands return the same results to the client.

First question: Is that a correct interpretation?

So for example, if registrar X creates domain Y with an appropriate
<domain:create> command and follows that with an identical epp command, both
commands have the same effect (either both succeed or both fail) and with
exactly the same result epp response.

Second question: Is that example correct?

If the above are true, it follows for example that the EPP server needs to
keep a certain degree of history. For example if registrar X deletes domain
Y, and actions the same command again, the server needs to remember that
domain Y used to belong to registrar X in order have the same effect and
return identical responses each time. This is not necessarily a problem; we
do that kind of thing anyway.

If all the above are correct interpretations of idempotency in EPP, it
follows that it also applies to changing passwords, so for example if
registrar X changes its password from Y to Z, the server needs to store not
only the current password but also the previous password for each registrar.

Can someone confirm or deny this interpretation for me? Thanks.

Rob Burbidge

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From: Eric Brunner-Williams in Portland Maine <[email-masked]>
Date: Thu, 27 Jun 2002 16:19:07 -0400

The subject has come up a few times. You can look at the following:

03/02 "Hollenbeck, Scot  Updated EPP Specification with Examples<<This me
08/15 Mark Nottingham    PROVREG and XML Protocol<<[ I'm posting this mes
08/15 Rick H Wesson      Re: PROVREG and XML Protocol<<Mark, I looked at 
08/15 Mark Nottingham    Re: PROVREG and XML Protocol<<Rick, So, if the w
08/15 Rick H Wesson      Re: PROVREG and XML Protocol<<Mark, frankly when
09/05 Edward Lewis       Provreg minutes from London<<--============_-121
09/07 Jaap Akkerhuis     Provreg minutes from London, repost<<Yester>>
09/17 Sheer El-Showk     RE: interpretation of 'EPP idempotency'<<> Comma
09/18 Thomas Corte       RE: interpretation of 'EPP idempotency'<<Hello, 
09/18 "Hollenbeck, Scot  RE: interpretation of 'EPP idempotency'<<It's ap
09/18 Thomas Corte       RE: interpretation of 'EPP idempotency'<<Hello, 
09/18 "Hollenbeck, Scot  RE: interpretation of 'EPP idempotency'<<>-----O
09/18 Daniel Manley      Re: interpretation of 'EPP idempotency'<<Thomas,
09/18 "Hollenbeck, Scot  RE: interpretation of 'EPP idempotency'<<<Scott/
09/19 "Hollenbeck, Scot  Command Recovery (was RE: interpretation of 'EPP
09/19 Daniel Manley      Re: interpretation of 'EPP idempotency'<<Hollenb
09/19 Dave Crocker       Re: Command Recovery (was RE: interpretation of 
09/21 Sheer El-Showk     Re: interpretation of 'EPP idempotency'<<Hi Scot

Eric