On Thu, Feb 16, 2017 at 1:19 PM, Martin Bjorklund <[email protected]> wrote:
> "Xufeng Liu" <[email protected]> wrote: > > > > > > > -----Original Message----- > > > From: i2rs [mailto:[email protected]] On Behalf Of Martin > Bjorklund > > > Sent: Tuesday, February 14, 2017 11:41 AM > > > To: [email protected] > > > Cc: [email protected] > > > Subject: Re: [i2rs] modeling options for draft-ietf-i2rs-yang-network- > topo > > > > > > Kent Watsen <[email protected]> wrote: > > > > > > > > > > > > [moving yang-doctors to BCC] > > > > > > > > > > > > >> OPTION 1: separate /foo and /foo-state trees > > > > >> -------------------------------------------- > > > > >> > > > > >> This option was/is described here: > > > > >> https://www.ietf.org/mail-archive/web/i2rs/current/msg04316.html. > > > > >> > > > > >> PROS: > > > > >> a) does NOT break legacy clients (how we got here) > > > > >> b) consistent with convention used in many IETF modules > > > > >> c) able to show if/how opstate may differ from configured values > > > > >> > > > > >> CONS: > > > > >> a) questionably valid YANG leafref usage > > > > > > > > > > What does this mean? > > > > > > > > I'm referring to how the description statement explains that the > > > > server may look to operational state in order to resolve the leafref, > > > > which is to result in behavior similar to pre-configuration in RFC > > > > 7223. > > > > > > Ok, I didn't pay close attention to the proposal in the quoted email. > > > > > > I would design this a bit differently. The config true leaf > "dependency" > > should > > > have a leafref to the config false node name, with require-instance > false. > > The > > > description should explain that the configuration item will be used by > the > > server > > > if all dependencies exist. When the configuration item is used, it > shows > > up in the > > > config false list. > > > > > > This way, the leafref usage is valid and straight forward. > > > > > > > >> b) complex server implementation (to handle require-instance > > > > >> false) > > > > > > > > > >Can you elaborate on this one? > > > > > > > > This is primarily a reflection of the CON listed above, in that it > > > > seems that a server would need to have special handling for when > > > > dependencies transition from being present to not-present and vice > > > > versa, much like the code to handle when a physical card is plugged > in > > > > or removed. > > > > > > Yes, but I think this is inherent to the problem at hand. Even with > the > > config true > > > solution defined in the current draft, it is not clear how things that > > were created > > > by the server would be deleted (if there were references to them). > > > > > > > Note: I should've listed this as a CON for OPTION 2 as well. > > > > > > > > > > > > > > > > >> c) eventually the module would need to migrate to the long-term > > > > >> solution, which would result in needing to also rewrite all > > > > >> modules that have augmented it (e.g., ietf-te-topology). > > > > >> d) leafref path expressions really only work for configuration > > data, > > > > >> though a clever server could have a special ability to peak > at > > > > >> the opstate values when doing validations. Of course, with > > > > >> require-instance is false, the value of leafref based > validation > > > > >> checking is negated anyway, even for config true nodes, so > this > > > > >> may not matter much. > > > > >> > > > > >> > > > > >> > > > > >> OPTION 2: explicit client-option to also return tagged opstate > data > > > > >> ------------------------------------------------------------ > ------- > > > > >> > > > > >> This option takes a couple forms. The first is module-specific > and > > > > >> the second is generic. In both cases, the idea is modeled after > > > > >> the with-defaults solution (RFC6243), wherein the client passes a > > > > >> special flag into <get-config> causing the server to also return > > > > >> opstate data, having a special metadata flag set, intermingled > with > > > > >> the configuration data. > > > > >> > > > > >> > > > > >> 2A: Module-specific version > > > > >> > > > > >> module foo { > > > > >> import ietf-netconf { prefix nc; } > > > > >> import ietf-yang-metadata { prefix md; } > > > > >> md:annotation server-provided { > > > > >> type boolean; > > > > >> } > > > > >> container nodes { > > > > >> config true; > > > > >> list node { > > > > >> key "name"; > > > > >> leaf name { type string; } > > > > >> leaf dependency { > > > > >> type leafref { > > > > >> path "../node/name" > > > > >> require-instance false; > > > > >> } > > > > >> } > > > > >> } > > > > >> } > > > > >> augment /nc:get-config/nc:input { > > > > >> leaf with-server-provided { > > > > >> type boolean; > > > > >> } > > > > >> } > > > > >> } > > > > > > > > > > I don't think this solution is substantially different from the > > > > > solution in draft-ietf-i2rs-yang-network-topo-10. You have just > > > > > moved a config false leaf to a meta-data annotation. This solution > > > > > suffers from the same problems as the solution in > > > > > draft-ietf-i2rs-yang-network-topo-10. > > > > > > > > There are two primary differences: > > > > > > > > 1) It doesn't break legacy clients > > > > > > The solution in the draft doesn't break legacy clients either - > there's a > > config > > > false leaf among the config true. No problem. > > > > > > > , because it requires the client to > > > > explicitly pass a 'with-server-provided' flag in the <get-config> > > > > request in order to get back the extended response. Likewise, it > > > > doesn't break backup/restore workflows, as the server can discard > > > > any 'server-provided' nodes passed in an <edit-config> operation. > > > > > > Huh? This goes against the defined behavior of 6241 + 7950. This is > the > > main > > > problem with the solution in the current draft. > > > > > > If a client sends a <get-config> for data in running, the server cannot > > send back > > > data that is not in running. > > > > > > > Lastly, it doesn't break <lock>/<unlock>, as there is no > comingling > > > > of opstate data in the 'running' datastore. > > > > > > > > 2) It doesn't say anything about how the opstate data is stored on > the > > > > server. The opstate data is not modeled at all. This approach > > > > only defines a presentation-layer format for how opstate data can > > > > be returned via an RPC. The server is free to persist the opstate > > > > data anyway it wants, perhaps in an internal datastore called > > > > 'operational-state' or in an uber-datastore with the opstate data > > > > flagged with a datastore='oper-state' attribute. Regardless, it's > > > > an implementation detail, and the conceptual datastore model is > > > > preserved. > > > > > > You are essentially defining a new operation, but do it by modifying > the > > > semantics of an existing one. I don't think this is a good idea; it is > > better to > > > define a new rpc. > > > > [Xufeng] Is using a new rpc is acceptable? If so, this could be a viable > > option. > > The draft-ietf-netmod-revised-datastores proposes a new rpc (maybe > <get-data>) to return data from the new operational-state datastore. > This is IMO better than adding opstate nodes to the reply to a > <get-config> request. > > +1 There are billions of combinations of letters than can be used as YANG identifiers. The letters "get-config" are already used. Pick a different combination. > > /martin > Andy > > _______________________________________________ > i2rs mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/i2rs >
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