Hi Per, This is a good news, but, please, help us out. Consider, we have a node - "te-tunnel" - which among other attributes has two key leafref lists: 1) each member of the 1st list points to a "connection" supporting the te-tunnel. All connections supporting all te-tunnels are stored in a single list of connections. 2) each member of the 2nd list points to a supporting "te-tunnel" - the te-tunnel in question depends on. All te=tunnels including the te-tunnel in question, are stored in a single list of te-tunnels.
The question: how the client can retrieve via a single request all attributes of the te-tunnel in question along with all parameters of all connections supporting the te-tunnel, but with just pointers to supporting te-tunnels (so that the interested client can use the pointers to retrieve full data via subsequent separate requests) ? Likewise, how the client can ask for full data of the te-tunnel and all supporting te-tunnels and just pointers for supporting connections? I really appreciate your help, Igor -----Original Message----- From: Per Hedeland [mailto:[email protected]] Sent: Monday, October 09, 2017 5:21 PM To: Igor Bryskin Cc: [email protected]; [email protected]; [email protected]; [email protected] Subject: Re: [Netconf] [netmod] Retrieving Information Pointed by leafref Just to be clear: what we're suggesting is that you can use the already-existing standard NETCONF XPath capability to achieve the desired result - see https://tools.ietf.org/html/rfc6241#section-8.9 --Per On 2017-10-09 21:52, Igor Bryskin wrote: > I agree. For example, a leafref may point not to a singls entity, but to a > list of entities, and the client might want to expand all of them into the > joint get response. > > Igor > > *From:*Per Hedeland > *To:*Martin Bjorklund, > *Cc:*Igor Bryskin,[email protected],[email protected],[email protected], > *Date:*2017-10-09 15:12:22 > *Subject:*Re: [Netconf] [netmod] Retrieving Information Pointed by leafref > > On 2017-10-09 19:13, Martin Bjorklund wrote: >> Igor Bryskin <[email protected]> wrote: >>> >>> Hi Per, >>> >>> Basically, what we need is a way for a client to request something >>> like this: >>> >>> get <XPath> joint with <XPath1, XPath2, ..., XPathn> >> >> ... which is what Per's expression does! Note that "|" in XPath means >> "union". >> >> But as Per explained, it only works in some cases (when the leafref >> acts a "single pointer"). > > Well, that particular expression works only in that case - but since it > is effectively the client that (perhaps based on the data model) decides > what the leafref-leafs "mean" (in this case the single key of a single > list), other cases can be handled the same way. E.g. multiple > leafref-to-key leafs that together give the keys of a multi-key list > just amounts to a slightly hairier XPath filter... > > --Per > >>> with a server interpreting the request as follows: >>> if a node pointed by XPath contains a pointer (e.g. key leafref) >>> matching one of the XPath from the "joint with" list, then the server >>> must provide the entire body of the node pointed by the pointer, >>> otherwise, just the pointer (as it happens today, that is, when no >>> "joint with" list specified). >>> >>> We think that this would allow for the client to optimize the number >>> of request-response iterations depending on application/use case. >>> >>> Regards, >>> Igor >> >> >> >> /martin >> >> >>> >>> >>> >>> >>> >>> >>> -----Original Message----- >>> From: Per Hedeland [mailto:[email protected]] >>> Sent: Monday, October 09, 2017 12:06 PM >>> To: Xufeng Liu >>> Cc: Igor Bryskin; [email protected]; [email protected] >>> Subject: Re: [Netconf] [netmod] Retrieving Information Pointed by >>> leafref >>> >>> I understand your use case, but a leaf of type leafref does not in >>> general identify a single node in the data tree - the leafref path >>> could >>> be for a non-key leaf, and/or the path could traverse list nodes, >>> and/or >>> the "target" list could have multiple keys and thus multiple >>> leafref-leafs be required to identify a specific list entry. >>> >>> Thus it seems to me that your use case is not a reasonable basis for a >>> new protocol operation. My XPath foo isn't very good either, but I do >>> believe Robert's suggestion of using an XPath filter could be a way >>> forward. I *think* the filter expression would be something along the >>> lines of >>> >>> /te/tunnels/tunnel[name='foo'] | >>> >>> /te/explicit-paths/explicit-path[name=/te/tunnels/tunnel[name='foo']/paths/path/explicit-path] >>> >>> --Per >>> >>> On 2017-10-09 15:42, Xufeng Liu wrote: >>>> Hi Per, >>>> >>>> >>>> >>>> *From:* Igor Bryskin [mailto:[email protected]] >>>> *Sent:* Sunday, October 8, 2017 7:04 PM >>>> *To:* Igor Bryskin <[email protected]>; [email protected]; >>>> *[email protected] >>>> *Cc:* [email protected]; [email protected] >>>> *Subject:* Re: [Netconf] [netmod] Retrieving Information Pointed by >>>> *leafref >>>> >>>> >>>> >>>> >>>> Hi Joel, >>>> >>>> Thanks, I think I didnt explain our problem correctly. >>>> >>>> In our case we have a leafref pointing to a te tunnel name, which >>>> happens to be a key to lookup the (axilary) tunnel. We need a way to >>>> include the entire tunnel body (not just a name) into the get >>>> response. This is to optimize the number of iterations between the >>>> client and the server. As Xufeng put it something similar to SQL join, >>>> >>>> Igor >>>> >>>> *From:*Igor Bryskin >>>> >>>> *To:*[email protected],[email protected], >>>> >>>> *Cc:*[email protected],[email protected], >>>> >>>> *Date:*2017-10-08 17:36:47 >>>> >>>> *Subject:*Re: [Netconf] [netmod] Retrieving Information Pointed by >>>> *leafref >>>> >>>> >>>> >>>> Hi Per, >>>> >>>> In a nutshell we would lika for a netconf client to have a way to >>>> instruct the server on whether in response to the get request the >>>> server needs to provide the entire body of a datastore node pointed >>>> to by a leafref or just a pointer to said node, so that the node's >>>> body could be retrieved by a subsequent separate request. This is >>>> requested by implementors who want to optimise rhe number of >>>> interactions between a client and its server. >>>> >>>> Cheers, >>>> Igor >>>> >>>> *From:*Per Hedeland >>>> >>>> *To:*Xufeng Liu, >>>> >>>> *Cc:*[email protected],'NetMod WG', >>>> >>>> *Date:*2017-10-08 14:01:27 >>>> >>>> *Subject:*Re: [Netconf] [netmod] Retrieving Information Pointed by >>>> *leafref >>>> >>>> >>>> >>>> On 2017-10-06 23:11, Xufeng Liu wrote: >>>>> During the design team discussion for TE and MPLS YANG modeling, we >>>>> have received a request from implementers: How to minimize the number >>>>> of NETCONF/RESTCONF RPCs to improve operation efficiency? >>>>> Especially for the case when the operator or client software needs to >>>>> retrieve the object contents pointed by a leafref. >>>>> >>>>> For example, given the following simplified TE tunnel model, >>>>> >>>>> +--rw te >>>>> >>>>> +--rw explicit-paths >>>>> >>>>> | +--rw explicit-path* [name] >>>>> >>>>> | +--rw name string >>>>> >>>>> | +--rw explicit-route-object* [index] >>>>> >>>>> | +--rw index uint32 >>>>> >>>>> | +--rw explicit-route-usage? identityref >>>>> >>>>> +--rw tunnels >>>>> >>>>> | +--rw tunnel* [name] >>>>> >>>>> | | +--rw name string >>>>> >>>>> | | +--rw paths >>>>> >>>>> | | | +--rw path* [name] >>>>> >>>>> | | | +--rw explicit-path? -> >>>>> | | | ../../../../../explicit-paths/explicit-path/name >>>>> >>>>> when the client tries to retrieve a tunnels information based on the >>>>> tunnel name, the get operation returns a list of leafrefs pointing >>>>> to the paths of the tunnel. >>>> >>>> Sorry, I'm afraid I don't follow. Can you explain exactly what your >>>> "get" request is (protocol and payload), and where the "list of >>>> leafref's" (whatever that may be) occurs in the reply? >>>> >>>> */[Xufeng] The get operation is the NETCONF/RESTCON <get> protocol >>>> *operation, or the <get-data> operation described in >>>> *https://tools.ietf.org/html/draft-dsdt-nmda-netconf-01 and the GET >>>> *operations >>>> on {+restconf}/ds/<datastore> described in >>>> https://tools.ietf.org/html/draft-ietf-netconf-nmda-restconf-00./* >>>> >>>> */ /* >>>> >>>> */We have a list of leafref values because in this example model, each >>>> *tunnel contains a list of paths, each of them contains a leafref. The >>>> * get returns a value for each instance of such a leafref, >>>> which (as a string value) will be used as a constraint (foreign key) >>>> to retrieve the instance of an explicit-path in the model above./* >>>> >>>> >>>> >>>> JFYI, in case there is some fundamental misunderstanding here: a leaf >>>> of >>>> type leafref has a single value - *one* of those that satisfy the >>>> leafref >>>> constraint, in case there are multiple "candidates". >>>> >>>> --Per >>>> >>>>> The client needs to issue at >>>>> least one more get operation to retrieve the path information about >>>>> the given tunnel. The request is to combine these two operations into >>>>> one. >>>>> >>>>> In the RDBMS SQL world, join can be used when SQL select is >>>>> performed, but NETCONF/YANG currently does not have this capability. >>>>> >>>>> Wed like to ask whether such a request is considered reasonable. >>>>> >>>>> If the request is reasonable, the next question is how to >>>>> proceed. This seems to be a protocol issue rather than YANG modeling >>>>> issue. Is it acceptable to add a new operation to achieve such a >>>>> <get-data> operation with expanded leafrefs? >>>>> >>>>> Comments and suggestions are appreciated. >>>>> >>>>> Thanks, >>>>> >>>>> - Xufeng >>>>> >>>>> >>>>> >>>>> _______________________________________________ >>>>> netmod mailing list >>>>> [email protected] <mailto:[email protected]> >>>>> https://www.ietf.org/mailman/listinfo/netmod >>>>> >>>> >>>> _______________________________________________ >>>> Netconf mailing list >>>> [email protected] <mailto:[email protected]> >>>> https://www.ietf.org/mailman/listinfo/netconf >>>> >>> >>> _______________________________________________ >>> Netconf mailing list >>> [email protected] >>> https://www.ietf.org/mailman/listinfo/netconf >>> > _______________________________________________ netmod mailing list [email protected] https://www.ietf.org/mailman/listinfo/netmod
