Re: [netconf] restconf collections

Martin Björklund <mbj+ietf@4668.se> Thu, 01 October 2020 14:57 UTC

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Date: Thu, 01 Oct 2020 16:57:15 +0200 (CEST)
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To: kent+ietf@watsen.net
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From: Martin =?iso-8859-1?Q?Bj=F6rklund?= <mbj+ietf@4668.se>
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Subject: Re: [netconf] restconf collections
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Kent Watsen <kent+ietf@watsen.net> wrote:
> 
> 
> > On Oct 1, 2020, at 9:23 AM, Martin Björklund <mbj+ietf@4668.se> wrote:
> > 
> > Kent Watsen <kent+ietf@watsen.net> wrote:
> >> Hi Qin,
> >> 
> >>> Some opstate must be persisted, e.g., long-lived counters, logs, etc.,
> >>> but it’s a good point about other opstate not being persisted.
> >>> Perhaps “node-tags” can be used here, to differentiate which is
> >>> which…and servers can indicate if/how they support the ephemeral
> >>> opstate leafs in queries?
> >>> 
> >>> [Qin]:That's a good case for node tag, in earlier discussion, we
> >>> discussed operation type, which distinguishs cumulative statistics
> >>> value from current value. The case discussed here is very close to
> >>> operation type proposal discussed earlier.
> >> 
> >> Yes.  Thank you for pointing that out.  I meant to make the same
> >> observation before.  Indeed, such node-tags could have dual-purpose:
> >> to guide a streaming-strategy and a querying-strategy for certain
> >> nodes.
> >> 
> >> 
> >>> Note sure how others feel about “direction: (c), but my primary
> >>> use-case revolves around time-series data (e.g., logs), where the
> >>> interest is commonly on the most-recent entries, so
> >>> "reverse-->offset—>limit” works nicely.
> >>> 
> >>> Perhaps an alternative would be to lift a concept from Python with
> >>> negative indexes so, for instance, offset=-N and limit=-N gives the
> >>> last N entries?
> >>> [Qin]: Yes, that's what I thought as well, with negative indexes, (b)
> >>> and (c) seems to me, can be combined.
> >> 
> >> Can others comment on this?
> > 
> > Isn't this just another syntax for the same function?
> 
> No, it is not.

How so?  Isn't the idea that you can first ask for offset=-10, then
-20, etc, essentially walking the list backwards?  (I don't understand
what a negative limit means though).


/martin


> 
> K.
> 
> 
> > 
> > /martin
> > 
> > 
> >> Presumably, we could eliminate “direction” (c) with this approach.  
> >> 
> >> Without “direction”, I think that UIs can still support the ability to
> >> do column-sorts, whereby the user clicks on a column’s header to
> >> toggle ascending vs. descending presentation, but they’ll have to do
> >> it client-side.
> >> 
> >> That is, if wanting to see the 2nd page of results sorted by a column,
> >> something like:
> >> 
> >> 	sort(column-name) --> offset(-2*pagesize) --> limit(pagesize)
> >> 
> >> Followed by the client then flipping the results to present the
> >> results in the user-selected order, right?
> >> 
> >> That said, given that DB-backends that support sorts commonly also
> >> support direction, it's unclear what this buys us.
> >> 
> >> 
> >>>>> Sure, but I wonder if, e.g., a netmask filter, is supportable by 
> >>>>> common DB-backends.  I’m hoping we have some DB-experts on the list!
> >>>> 
> >>>> See above.  It can be quite efficient even if the backend doesn't 
> >>>> support it.
> >>> 
> >>> I don’t see that above, but I don’t doubt that it can be so, it’s just
> >>> a whole lot of implementation complexity.  It seems that we
> >>> should/must support servers doing it, we just need to find a way
> >>> (node-tags?) to enable them to express that ability.
> >>> [Qin]: My feeling is this efficiency more depends on the amount of
> >>> data we need to request. If amount of data we request is huge, maybe,
> >>> client-> server-> backend may be the better choice.
> >> 
> >> Is it the amount of data requested or the number of entries in the
> >> list?  At least, in my worldview, clients are always requesting a
> >> “page” of data, so that part is rather consistently small.
> >> 
> >> If the intention is to get a complete dump, then maybe the comment
> >> from yesterday applies, whereby streaming to an external repository
> >> that can be queried offline makes more sense?  - especially
> >> considering that the number of on-box logs is likely to be only the
> >> most recent (e.g., days), whereas the complete-dump type queries
> >> likely wish to extend well-past that.
> >> 
> >> K.
> >> 
> >> 
>