[netconf] Re: RFC 8040/8527: ETags on /ds/operational?

[Tomáš Pecka <[e-mail]>]

Hello Kent,

thanks for the reply and the intended interpretation.

I understand the mechanisms are used in place of locking. I was confused 
that RFC 8527 does not say anything about not supporting them on 
read-only datastores (as it does, for instance, in Section 3.2 about 
write operations on <intended>), while RFC 8040 says the server MUST 
support them for the datastore resource. I probably read the document 
too literally, hence the confusion.

Re {+restconf}/data (not) being available: I think that removing it 
would contradict Section 1 (Introduction) of RFC 8527. It explicitly 
says that RFC 8527 is backwards compatible with RFC 8040.

Best,
Tomas

Dne 07. 10. 26 v 1:46 Kent Watsen napsal(a):
> Hi Tomáš,
> 
> HTTP ETags and Last-Modified are primarily, if not exclusively, for optimistic locking, used by RESTCONF in lieu of the explicit locking mechanism used by NETCONF.  It only makes sense to use them on read/write datastores, e.g., running, candidate, startup, and system (if supported by the server).   It doesn't make sense for a server to support ETags on a read-only datastores, e.g., factory-default, intended, and operational.
> 
> PS: if supporting NMDA, I wouldn't expect {+restconf}/data to be available.  That said, I do not see support for that statement in RFC 8527.
> 
> Kent
> 
> 
>> On Oct 6, 2026, at 3:17 PM, Tomáš Pecka <tomas.pecka=[e-mail]> wrote:
>>
>> Hi all,
>>
>> We are implementing entity-tag and Last-Modified support in rousette [1], a RESTCONF server built on top of sysrepo. We have NMDA support, and RFC 8527 is silent on entity-tags for the {+restconf}/ds/<datastore> resources.
>>
>> RFC 8040 (Section 3.4.1.2) says the server MUST maintain an entity-tag for the datastore resource that tracks only configuration data, and that it is for running when co-located with a NETCONF server, which is our case. RFC 8527 (Section 3.1) defines {+restconf}/ds/<datastore> as datastore resources.
>>
>> We therefore plan to return running's ETag and Last-Modified on {+restconf}/ds/ietf-datastores:operational, the same as on {+restconf}/data. Intuitively, though, such an ETag and Last-Modified seem to be of limited use there, because the operational datastore contains mostly state data. Is returning running's ETag there the intended reading?
>>
>> Thanks,
>> Tomas Pecka
>>
>> [1] https://github.com/CESNET/rousette
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