Hi Rob, This helps a lot. What you wrote will work.
The only difference is that if we would have the "joimt with" clause as we proposed, the server would be able to tailor the te-tunnel presentation to the client's requirements, e.g. substituting the connection pointers with connection bodies, while, according to your suggestion, the server will provide the te-tunnel body as is, and then augment it with the cobbection information, thus, leaving for the client to "shuffle " the received data. But I do agree, this would be a minor inconvinience for the client, the important thing is that the client will get all the data in one piece. Thanks a lot, Igor c From:Robert Wilton To:Igor Bryskin, Cc:Per Hedeland,[email protected],[email protected], Date:2017-10-10 06:41:04 Subject:Re: [netmod] [Netconf] Retrieving Information Pointed by leafref Hi Igor, On 09/10/2017 23:11, Igor Bryskin wrote: > 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) ? I think that it might be something like this (for tunnel name foo): /te/tunnels/tunnel[name='foo'] | /te/connections/connection[name=/te/tunnels/tunnel[name='foo']/connections/connection/name] E.g. in English, this should equate to something like: Return all information for tunnel foo AND ALSO Return all information for all connections where the connection name matches one of the connections listed in tunnel foo. > > Likewise, how the client can ask for full data of the te-tunnel and all > supporting te-tunnels and just pointers for supporting connections? If my xpath above is right, then this would be something roughly like this: /te/tunnels/tunnel[name='foo'] | /te/tunnels/tunnel[name=/te/tunnels/tunnel[name='foo']/supporting-tunnels/supporting-tunnel/name] I'm an XPath novice, so the expressions might be wrong. https://www.freeformatter.com/xpath-tester.html might be useful. E.g. if you can construct a simple XML instance tree of your data, you could validate whether the XPath expression works. I hope that this is of some help, Rob > > 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 > . >
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