On Tue, 2017-12-19 at 07:49 -0500, Lou Berger wrote:
On 12/19/2017 7:36 AM, Ladislav Lhotka wrote:
On Tue, 2017-12-19 at 06:43 -0500, Lou Berger wrote:
Hi Lada,
On 12/19/2017 6:23 AM, Ladislav Lhotka wrote:
On Tue, 2017-12-19 at 06:20 -0500, Lou Berger wrote:
Lada,
On December 19, 2017 1:12:35 AM Ladislav Lhotka <lho...@nic.cz>
wrote:
On Mon, 2017-12-18 at 15:30 -0500, Lou Berger wrote:
lada,
See below.
On 12/15/2017 8:59 AM, Ladislav Lhotka wrote:
Hi,
unfortunately, using an action for querying embedded YANG
library
data
(needed for the "inline" case of schema mount) doesn't work
either
because now under NMDA actions can be used only on instances
in
the
<operational> datastore.
but the inline/embedded library would (only) be present in the
in
the
operational datastore, so what's the issue?
Well, the issue is described in my initial mail of this thread:
the
current
text
requires that every instance of an inline mount point contains
the
embedded
YANG library. Tha latter is state data, so the above requirement
cannot
be
satisfied if the mount point instance is in a configuration
datastore.
That's not how I read the intent of the current text. I don't see
SM
impacting which data stores information is presented. Just like
use
of
scheme mount doesn't transform RO configuration information into
operational information. I sent you a couple of sentences
clarifying
this
at one point, I'll dig up the proposed text and resend.
Please do, this has to be discussed in the WG mailing list.
Agreed - that's why I asked to start this thread!
Here's the original proposal:
How about at the end of the section [3.2] adding a new
paragraph along the lines of:
It is important to note that both YANG Library and Schema
Mount Modules contain only operational state data. As such,
s/contain/define/
the information in these modules should be retrieved by
clients from operational data stores using the appropriate
This is based on two assumptions:
1. For every configuration datastore there is a corresponding
operational
datastore.
well the text is revised below. In any case, "these modules" refers to
yang library, and yes, I'm assuming YL is always and only in
operational. If the revised text below isn't clear s/these/YANG Library/
-
The thing is that we have the top-level YANG library in <operational>, and
then
embedded YANG libraries scattered inside inline mount point instances.
2. For every mount point instance in any configuration datastore there
is a
corresponding mount point instance (with the same path) in an
operational
datastore.
I think that neither of these has to be true in general.
agreed in general, but for inline, where YL is required, it must be true.
How do you know? I provided an example in Singapore where a mount point
instance
in <intended> is a part of pre-provisioned data (for non-existent hardware).
Then, according to the NMDA rules there is no corresponding instance in
<operational>, hence no place where the embedded YANG library can be placed.
(I can easily provide a concrete example if needed).
Dean replied that this cannot happen, so it seems there are some assumptions
how
the inline method of schema mount may be applied. If so, these assumptions
have
to be explicitly stated.
protocol operations.
In contrast, the substance of my proposal with metadata annotations is
to be
able to retrieve all schemas from a well-known location in *the*
<operational>
datastore, namely from the top-level YANG library.
What about a schema that is based on dll that contains modules that
isn't loaded until a mount point is instantiated -- this is certainly a
valid approach for supporting LNEs, but would be precluded in this
approach. I really don't think a top level approach works for all
inline (managed) types of mounts.
It isn't precluded: when the mount point is instantiated (no matter which
datastore it is in), the server adds the schema as a new entry to the
"schema"
list in the top level YANG library (with a unique key), and annotates the
mount
point instance with a leafref pointing to that key. So different instances
of
the same mount point can have different schemas.
Given this discussion, we can generalize it further to:
The use of mount points does not impact the nature of the
mounted data or in which data store information is made
available. For example, mounted YANG Library modules contain
only operational state data and, as such, the information in
these modules is available from operational data stores using
the appropriate protocol operations.
The whole question here is whether and how we can locate the schema for
an
inline mount point in any configuration datastore.
Why is a mounted YL different than a top level YL? What works for and
It is not different, but it can be only in an operational datastores, and so
for
mount point instances inside configuration datastores we need a way how to
locate the schema for that mount point, because it cannot be found directly
under the mount point instance (as the current text assumes).
is sufficient for the normal case of YL shouldn't be impacted or
modified by SM -- at least that's how I thought we've been talking about
since SM was started. Again, we never made any special provisions for
any other rw/ro/state data, assuming top level YL is not handled as
metadata, why start now?
I'm getting the impression that your argument may be more about if YL
should be treated as something other than operational data, is this wrong?
This is wrong. My argument is that there should be only one top-level YANG
library (state data) and each inline mount point instance just points to a
schema inside it by means of a metadata annotation attached to the mount
point
(in any datastore).
Lada
Thanks,
Lou
Lada
Lou
Lada
Lou
However, a good alternative seems to be a metadata
annotation
along
the
lines of RFC 7952, for example with the alternative B of the
newly
proposed YANG library schema:
md:annotation schema-ref {
type leafref {
path "/yanglib:yang-
library/yanglib:schema/yanglib:name";
}
}
In other words, all inline mounted schemas would be included
in
the
top-level YANG library, and mount point instances in all
datastores
would be annotated with leafref pointing to the actual
schema.
Unlike regular state data, it is IMO no problem to permit
such
annotations in configuration datastores.
Opinions?
I'm not sure this will work for all architectures of LNEs as
well
as
other possible future use cases. In short, this seems *very*
restrictive.
I don't understand, IMO it is not restrictive at all. What kind
of
restrictions
do you see?
Lada
Lou
Thanks, Lada
Ladislav Lhotka <lho...@nic.cz> writes:
Hi,
the following text in sec. 3.2 of schema-mount-08 is wrong
for
traditional
datastores, and even more so for NDMA:
In case 1 ["inline"], the mounted schema is determined
at
run
time:
every
instance of the mount point that exists in the parent
tree
MUST
contain a copy of YANG library data [RFC7895] that
defines
the
mounted schema exactly as for a top-level data
model. A
client
is
expected to retrieve this data from the instance tree,
possibly
after
creating the mount point. Instances of the same mount
point
MAY
use
different mounted schemas.
An instance of the mount point in any *configuration*
datastores
cannot
contain
YANG library (being state data), and so the MUST cannot
hold.
It is not clear to me how to repair this without
considerable
complications
and/or a lot of handwaving. There is actually one good
solution
but it
has
impact on YANG library: the server could provide it in a
reply
to
an
operation,
say "get-yang-library" rather than as state data. Then
everything
would be
fine
- this operation would turn into an action for the mount
point,
and it
can
be
used equally well for config true and false mount points.
So my proposal is to move from YANG library as state data
to
an
operation.
It
could be done along with changing the YANG library
structure,
so
there
will be
little extra impact on implementations.
Lada
--
Ladislav Lhotka
Head, CZ.NIC Labs
PGP Key ID: 0xB8F92B08A9F76C67
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--
Ladislav Lhotka
Head, CZ.NIC Labs
PGP Key ID: 0xB8F92B08A9F76C67
