Re: [netconf] XPath support in RESTCONF

["Per Andersson (perander)" <[e-mail]>]

Andy Bierman <[e-mail]>:
>On Tue, Dec 5, 2023 at 9:50 AM Per Andersson (perander) <[e-mail]<mailto:[e-mail]>> wrote:
>>Andy Bierman <[e-mail]<mailto:[e-mail]>>:
>>>
>>> The 'get' or 'get-config' operation can be used.
>>> The filter element is part of the payload, not the request URI.
>>> This supports a 'select' attribute which is set to the XPath expression.
>>
>> This is a very NETCONF way to use RESTCONF though. It would
>> probably be more appreciated to actually use HTTP techniques and
>> mechanics.
>
> No -- this is the way RFC 8040 defines to invoke a YANG rpc-stmt.
>
> IMO every RESTCONF server should provide access to all the RPC operations
> that are advertised as implemented in the YANG library.

I agree with this of course.


> The syntax is very simple and it does not require a new RESTCONF protocol version.
>
>
> POST /restconf/operations/ietf-netconf:get-config HTTP/1.1
> Server: example.com<http://example.com>
> Content-Type: application/yang-data+xml
>
> <input xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
>   <filter type="xpath"
>          xmlns:if="urn:ietf:params:xml:ns:yang:ietf-interfaces"
>          select="/if:interfaces/if:interfaces[if:name='eno1']"/>
> </input>

Indeed.

Perhaps good enough.

However this would not support e.g. pagination as the current list-pagination
draft defines it. Which a XPath query draft could include/update. Another option
could be to bolt on pagination support for arbitrary RPC invocation, which
probably is a lot more work.


>>> I think it is a hard sell to state that one should use HTTP more or less
>>> as expected to fetch data, but if you want do advanced filtering it is
>>> necessary to invoke an RPC.
>
> The query language is even more advanced and complex to implement.
> IMO much more so than the standard POST already defined in RESTCONF.

Even so, "exclude" HTTP query parameter is asked for instead of invoking
a NETCONF get-config RPC.


--
Per