Hi Alex,
On Thu, Dec 15, 2016 at 10:04:05AM +0000, Alex Bligh wrote:
>
> > On 14 Dec 2016, at 20:18, Wouter Verhelst <w...@uter.be> wrote:
> >
> >> + * the server MAY return a context consisting of a namespace and
> >> + a colon only (i.e. omitting the leaf-name) to indicate that
> >> + the namespace contains a large number of possible contexts
> >> + within that namespace (for instance a namespace `X-backup` with
> >> + contexts that indicate whether blocks were written after
> >> + a given date might accept queries of the form
> >> + `'X-backup:modifiedtime>[unixdate]'` where `[unixdate]` is an
> >> + arbitrary integer, and in this case it might simply
> >> + return `X-backup:`)
> >
> > This is way too detailed, I think. It should just allow namespaces to
> > define what _LIST_ may return, as long as the client is somehow able to
> > distill (through knowledge of the spec as well as the information sent
> > in reply to the _LIST_ command) all the metadata contexts it can
> > possibly select.
>
>
> OK, this part now reads:
>
> The server MUST either reply with an error (for instance `EINVAL`
> if the option is not supported), or reply with a list of
> `NBD_REP_META_CONTEXT` replies followed by `NBD_REP_ACK`.
>
> If zero queries are sent, then the server MUST return all
> the metadata contexts that are available to the client to select
> on the given export with `NBD_OPT_SET_META_CONTEXT`, save that:
This reads a bit awkward. I would do:
s/save that:/except as explained below/
> If one or more queries are sent, then the server MUST return
> those metadata contexts that are available to the client to
> select on the given export with `NBD_OPT_SET_META_CONTEXT`,
> and which match one or more of the queries given. The
> support of wildcarding within the leaf-name portion of
> the query string is dependent upon the namespace.
>
> In either case, however, for any given namespace the
> server MAY, instead of exhaustively listing every
> matching context available to select (or every context
> available to select where no query is given), send
> sufficient context records back to allow a client with
> knowledge of the namespace to select any context. Each
> namespace returned MUST still satisfy the rules for
> namespaces (i.e. they must begin with the relevant
> namespace, followed by a colon, then printable non-whitespace
> UTF-8 characters,
Why restrict to non-whitespace characters? (printable makes sense...)
> with the entire string not exceeding
> 255 bytes). This may be helpful where a client can
> construct algorithmic queries. For instance, a client might
> reply simply with the namespace with no leaf-name (e.g.
> 'X-FooBar:') or with a range of values (e.g.
> 'X-ModifiedDate:20160310-20161214'). The semantics of
> such a reply are a matter for the definition of the
> namespace.
>
> Hope that works.
--
< ron> I mean, the main *practical* problem with C++, is there's like a dozen
people in the world who think they really understand all of its rules,
and pretty much all of them are just lying to themselves too.
-- #debian-devel, OFTC, 2016-02-12
