Hi,
Regarding the issue "Is it allowed to violate uniqueness of key
values?", https://github.com/netmod-wg/datastore-dt/issues/10
We have discussed this further, and would like to extend the text in the
draft to explicitly allow key uniqueness to be violated!
We have thought of several cases where it is possible that duplicate
entries could appear, and we don't want to force any overhead on the
device to guarantee that this does not occur, nor do we want to force
synchronization between configuration processing and what is reported in
<operational>. Of course, in normal circumstances this constraint, like
the others, should not be violated. This is already stated in the draft.
Examples of where uniqueness of list keys could be violated include:
1) If a device is internally paging the results back for a long list,
then it is possible that a entry could have been reported near the
beginning of the list, then moved, and then reported again at the end of
the list.
2) If the list being stored somewhere in the system has become corrupted
and contains duplicate entries. It is better to return truth.
3) On a distributed system where the list is being constructed from
multiple nodes (e.g. linecards or peer devices) then if a list entry is
moved from one node to another then it is again possible that an entry
could be reported in both places (or neither) for a short interval
before the system becomes consistent again.
Proposed text:
OLD:
<operational> SHOULD conform to any constraints specified in the data
model, but given the principal aim of returning "in use" values, it
is possible that constraints MAY be violated under some
circumstances, e.g., an abnormal value is "in use", or due to remnant
configuration (see Section 4.3.1). Note, that deviations are still
used when it is known in advance that a device does not fully conform
to the <operational> schema.
Only semantic constraints MAY be violated, these are the YANG "when",
"must", "mandatory", "unique", "min-elements", and "max-elements"
statements.
NEW:
<operational> SHOULD conform to any constraints specified in the data
model, but given the principal aim of returning "in use" values, it
is possible that constraints MAY be violated under some
circumstances, e.g., an abnormal value is "in use", the structure of
a list is being modified, or due to remnant configuration (see
Section 4.3.1). Note, that deviations are still used when it is
known in advance that a device does not fully conform to the
<operational> schema.
Only semantic constraints MAY be violated, these are the YANG "when",
"must", "mandatory", "unique", "min-elements", and "max-elements"
statements; and the uniqueness of key values.
Again, if there are no objections, I will apply this change.
Thanks,
Rob
On 14/09/2017 16:44, Balazs Lengyel wrote:
See below !
On 2017-09-14 16:32, Martin Bjorklund wrote:
CH 4.4.) "Validation is performed on the contents of <intended>."
This to me means that default data is not considered at validation
Note that RFC 7950, section 6.4.1, says:
In the accessible tree, all leafs and leaf-lists with default values
in use exist (see Sections 7.6.1 and 7.7.2).
So defaults are taken into account when intended is validated.
BALAZS: Yes the two seem to contradict each other. This can be
understood in your way, however the current text is not clear enough.
I would add:
Validation is performed on the contents of <intended> (EXTENDED WITH
DEFAULT CONFIGURATION).
which would be a backwards incompatible change. Also if validation
does not consider system configured data that would allow cases like
multiple interfaces named lo0. One from <intended> one from system
configuration. IMHO while it is OK to violate uniqueness because of
remnant data, the above violation of uniqueness seems a bad idea.
If your system adds data to <running>, or to <intended>, it will be
validated.
Ch. 4.7) Is it allowed to violate uniqueness of key values? IMHO it
should not be.
Agreed. Note that the draft explicitly lists the constraints that can
be violated, and uniqueness of keys is not listed.
BALAZS: If that is the intent I would propose to explicitly state it.
For me it was non-trivial.
Can a a choice statement be violated? Having to existing branches at
the same time? It seems a semantic constraint to me. IMHO yes.
Can an if-feature be violated? If support has just changed and we
have some remnant config, I can very well imagine it violated.
Also here could you change
If a node in <operational> does not meet the syntactic constraints
then it cannot be returned
to
If a node in <operational> does not meet the syntactic constraints
then it MUST NOT be returned
/martin
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