Re: New Version Notification for draft-nottingham-httpbis-retry-01.txt

Willy Tarreau <> Sat, 11 February 2017 07:24 UTC

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Date: Sat, 11 Feb 2017 08:19:46 +0100
From: Willy Tarreau <>
To: Mike Bishop <>
Cc: Wenbo Zhu <>, Mark Nottingham <>, HTTP Working Group <>, "Roy T. Fielding" <>
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Subject: Re: New Version Notification for draft-nottingham-httpbis-retry-01.txt
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On Sat, Feb 11, 2017 at 04:23:33AM +0000, Mike Bishop wrote:
> Some assorted reasons show up in the discussion at
> starting around 1:15:30.  Scale, I'm not sure; Patrick had the direct
> experience and might be able to tell more.

Thanks for the link, Mike, that was quite an interesting talk! For haproxy
I planned to have an action to let the admin indicate that if certain
criteria match, then a request is idempotent. For example, a POST request
containing a transactionId argument, etc... I'm realizing that stuff like
this could be proposed to be generalized instead of having to be made
specific to each and every component. In short what is needed (from my
perspective) is :
  - a way for the application to signal the client that a request will
    be idempotent (could be either by adding a specific field to HTML
    forms, or passing a header field in the HTTP response saying that
    the exact same URI is safe for POSTs, etc).

  - a way for the client to notify the chain back to the origin that
    it's safe to replay the current request based on the info learned
    from the application. That could simply be a header field or a
    value added to a header field such as :
        content-type: application/x-www-form-urlencoded; safe

Just my 2 cents,