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
