Re: Atomic patches and network interruptions

[Marius Kleidl <[e-mail]>]

Hello Glenn,

thank you for your comments!

> The server *application* handling the request could buffer and store the
  (partial) request body fragments, allowing for resumable uploads, and
  then apply the changes only once the entire patch document is received

That's an interesting idea. Would the client in such a scenario be able to
query the state of the buffered body fragments through a request? Or would
this not be easily possible because the fragments collection is not a
resource on its own and thus cannot be the target of a request?

Best regards
Marius Kleidl


On Mon, Feb 26, 2024 at 10:41 PM Glenn Strauss <
[e-mail]> wrote:

> On Mon, Feb 26, 2024 at 08:30:38PM +0100, Marius Kleidl wrote:
> > Dear working group,
> >
> > RFC 5789, which defines the PATCH method, places this requirement:
> >
> > The PATCH method requests that a set of changes described in the request
> > > entity be applied to the resource identified by the Request-URI. The
> set of
> > > changes is represented in a format called a "patch document"
> identified by
> > > a media type.
> > > [...]
> > > The server MUST apply the entire set of changes atomically and never
> > > provide (e.g., in response to a GET during this operation) a partially
> > > modified representation. If the entire patch document cannot be
> > > successfully applied, then the server MUST NOT apply any of the
> changes.
>
> This is very direct and very explicit.  "atomically" means exactly that.
>
> > > If the entire patch document cannot be
> > > successfully applied, then the server MUST NOT apply any of the
> changes.
>
> The server MUST NOT apply an incomplete patch document.  No exceptions.
>
> Among your options:
> The client can send smaller patch documents if changes are independent.
>   (recommended)
> The server *application* handling the request could buffer and store the
>   (partial) request body fragments, allowing for resumable uploads, and
>   then apply the changes only once the entire patch document is received
>
> > Or could this be allowed if the
> > corresponding media types explicitly allows applying partial content?
>
> More questionable: a PATCH format might be defined/extended with a new
>   media-type defining a format that consists of multiple patch documents
>   which may be applied independently.  The client would need some way(s)
>   to query/validate which patch documents were applied.  Again, per the
>   RFC, each patch document must be applied atomically; never partially.
>
> Cheers, Glenn
>