On Fri, Aug 21, 2015 at 6:01 AM, Martin Bjorklund <[email protected]> wrote:
> Robert Wilton <[email protected]> wrote: > > Hi Martin, > > > > On 20/08/2015 09:15, Martin Bjorklund wrote: > > > Andy Bierman <[email protected]> wrote: > > >> On Wed, Aug 19, 2015 at 4:25 AM, Martin Bjorklund <[email protected]> > > >> wrote: > > >> > > >>> Robert Wilton <[email protected]> wrote: > > >>>> > > >>>> On 18/08/2015 18:22, Andy Bierman wrote: > > >>>>> This is how languages like SMIv2 and YANG work. > > >>>>> A conceptual object is given a permanent "home" within the tree of > > >>>>> object identifiers. > > >>>>> Moving data is very expensive, since any clients working with the > old > > >>>>> data > > >>>>> will break as soon as the data is moved. > > >>>>> > > >>>>> I am not convinced the IETF can or should come up with a set of > > >>>>> containers > > >>>>> that covers every possible topic that can be modeled in YANG. > > >>>> I mostly agree, but having some more structure/advice as to where to > > >>>> place YANG modules may be helpful. I'm thinking more along the > lines > > >>>> of broad categories rather than precise locations. > > >>> +1 > > >>> > > >>>>> If someone wants to builds a YANG controller node that is > managing > > >>>>> the configuration for a network of devices then wouldn't they > want > > >>>>> a particular device's interface configuration to be located > > >>>>> somewhere like > /network/device/<device-name>/interfaces/interface? > > >>>>> Ideally, they would be able to use the same YANG definitions > that > > >>>>> are defined for /interfaces/ but root them relative to > > >>>>> /network/device/<device-name>/. > > >>>>> > > >>>>> > > >>>>> > > >>>>> Yes -- some of us (like Martin) have pointed this out many times. > > >>>>> The "device" container on an NE does not help at all wrt/ > > >>>>> aggregation on a controller. "/device" or "/" work the same for > this > > >>>>> purpose. > > >>> Actually, I would argue that / works better. On the controller, you > > >>> probably have a list of devices you control (this is how our NCS > > >>> works, and how ODL works (I have been told)): > > >>> > > >>> container devices { > > >>> list device { > > >>> key name; > > >>> // meta-info about the device goes here, things like > > >>> // ip-address, port, auth info... > > >>> container data { > > >>> // all models supported by the devices are "mounted" here > > >>> } > > >>> } > > >>> } > > >>> > > >>> So on the controller, the path to interface "eth0" on device "foo" > > >>> would be: > > >>> > > >>> /devices/device[name='foo']/data/interfaces/interface[name='eth0'] > > >>> > > >>> if we also have a top-level "/device" container we'd have: > > >>> > > >>> > /devices/device[name='foo']/data/device/interfaces/interface[name='eth0'] > > >>> > > >>>> What would the real resource location for > > >>>> "/network/device/<device-name>/interfaces/interface" be? > > >>> I don't think there is such a thing as a "real" location. The path > is > > >>> scoped in the system you work with; in the controller it might be as > I > > >>> illustrated above, in the device it starts with /interfaces, but in a > > >>> controller-of-controllers it might be: > > >>> > > >>> /domains/domain[name='bar']/devices/device[name='foo']/data > > >>> /interfaces/interface[name='eth0'] > > >>> > > >>> Currently we have a proprietary way of "relocating" YANG modules, and > > >>> ODL has its "mount", and I think Andy has some other mechanism. > Maybe > > >>> the time has come to standardize how mount works, and maybe then also > > >>> standardize the list of devices in a controller model. > > >>> > > >>> > > >> +1 > > >> > > >> We just need to standardize a "docroot within a docroot". > > >> This is not relocation of subtrees within the datastore, this is just > > >> mounting > > >> a datastore somewhere within a parent datastore. > > >> > > >> In YANG validation terms, you simply adjust the docroot to the nested > > >> mount > > >> point, > > >> and the replicated datastore can be used as if it were stand-alone. > > >> This would allow any sort of encapsulation of datastores and not add > > >> any > > >> data model complexity to devices which do not have virtual servers > > >> (most of them). > > > Compared to the mount draft, I would like to decouple the schema > > > information from the instance population mechanism. I.e., I'd like a > > > mechanism that simply defines the schema, not necessarily how the data > > > is populated (in the mount draft data was fetched from a remote > > > server, but IMO that is just one of several use cases). > > Yes, I agree that these could/should be decoupled. Although I note > > that the mount draft does also allow for local mounts, although this > > does not seem to be intended to be the mainline case. > > > > > > > > I can think of two ways to do this. > > > > > > 1) Your "ycx:root" statement. This is open-ended, so we could do: > > > > > > list logical-element { > > > key name; > > > leaf name { ... } > > > yang-root true; > > > } > > > > > > From a schema perspective, any top-level node from any data model > > > could be used within the logical-element list. > > > > > > 2) Cherry-picking: > > > > > > list logical-element { > > > key name; > > > leaf name { ... } > > > mount if:interfaces; > > > mount sys:system; > > > ... > > > } > > I think that that it makes the overall schema more useful if it > > explicitly states what schema is used for the mounted nodes, although > > possibly a wildcard mount could still be allowed. > > > > I wasn't quite sure how it would work if you wanted to mount a schema > > that has augmentations. Would you have to list all supported > > augmentations in the mount point as well? Otherwise you wouldn't know > > what the full schema is. > > My idea is that you mount the top-level node, and that means that > everything below it is "copied" into the new location. I.e., > augmentations to the subtree are also copied. So you would not mount > any augmentations (that's why the syntax is mount <top-level-node>). > > > I am only interested in (1) ncx:root approach because this actually works. Cherry-picking does not work well because (a) subtrees are allowed to have constraints on data outside that subtree (b) YANG XPath cannot be safely relocated up or down (i.e., move /interfaces to /device/interfaces or move /foo/bar/baz to /foo2/baz /martin > Andy > > > > > > Thanks, > > Rob > > > > > > > > > > Or maybe combine them into one "mount" statement: > > > > > > mount *; // allow any top-level node > > > mount sys:system; // allow this specific top-level node > > > > > > > > > > > > /martin > > > > > > . > > > > > >
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