Juergen Schoenwaelder <j.schoenwael...@jacobs-university.de> wrote: > On Sat, Oct 27, 2018 at 06:50:58AM -0700, Andy Bierman wrote: > > > > This is what we have today only if modules are updated in legal ways. > > The 3.1 requirement says this backward compatibility is maintained even > > if the module is updated in violation of the module update rules. > > > > It is stating a requirement. How solutions meet the requirement is for > the solutions to figure out. > > > How would 3.1 be met if the WG decided to just add a new 'datastore' > > key leaf to the /modules-state/module list? > > Depends on the solution I guess. > > > IMO the current "deprecate and start over" is actually the easiest > > and most robust solution path, and it requires no changes to YANG or > > the protocols. > > Yep. But there are people who think that other solutions can do > better. The challenge is to find out whether they actually do better > or for whom they do better (and if someone has to pay a price for it). > For having this discussions, it is good to write down requirements. > > > > 3.2 The solution MUST provide a mechanism to allow servers to > > > simultaneously support clients using different revisions of > > > modules. A client's choice of particular revision of one or > > > more modules may restrict the particular revision of other > > > modules that may be used in the same request or session. > > > > > > Today, the version number is effectively an (implicit) part of the > > > module name (plus the revision date for backwards compatible changes). > > > Hence, my understanding is that today's model does satisfy 3.2 as > > > well. > > > > This is not what we have at all. RFC 7950 says a server can only implement > > one revision of a module. > > > > A new version today essentially means a new module name and I do not > see a conflict with what I wrote.
Then I think this requirement needs clarification. It says "different revision of modules", which can be interpreted as different revisions of *the same* module. Also the second part of the paragraph seems to indicate multiple revisions of the same module in the server. I do not agree with this requirement. /martin > > > > If we want to increase 'agility' in an attempt to make it easier to > > > deliver early designs and to fix them on the go, the costs will go up > > > somewhere. The extreme cases are: > > > > > > 1) The server can make changes to YANG modules in arbitrary ways and > > > the clients have to adapt, i.e., clients have to pay the bill. > > > > > > 2) The server has to provide strict backwards compatibility in order > > > to not break clients, i.e., servers have to pay the bill. > > > > > > > > This is not correct. Implementing multiple incompatible revisions of a > > module > > (e.g, "module" list keyed 2 different ways) is a huge bill to pay for the > > server developer. > > Depends on the details and the developer will decide based on the > impact on the clients and whether a transition period is possible. You > seem to read that the requirement says one has to implement backwards > compatibility. This is not what the text says. The text says it must > be possible. > > > > Unless we go for option 1) above, I believe 3.1 and 3.2 are valid and > > > important requirements. > > > > I do not agree with the premise that non-compatible data model updates are > > required. > > 3.1 can be achieved without such changes. 3.2 violates RFC 7950, requiring > > a new(much more complicated) version of YANG > > I think you misread the requirements text. > > /js > > -- > Juergen Schoenwaelder Jacobs University Bremen gGmbH > Phone: +49 421 200 3587 Campus Ring 1 | 28759 Bremen | Germany > Fax: +49 421 200 3103 <https://www.jacobs-university.de/> > > _______________________________________________ > netmod mailing list > netmod@ietf.org > https://www.ietf.org/mailman/listinfo/netmod > _______________________________________________ netmod mailing list netmod@ietf.org https://www.ietf.org/mailman/listinfo/netmod
