[dev] Northbound API - Presentation this Friday

[Renato Westphal]

On Fri, May 18, 2018 at 5:06 AM, Olivier Dugeon
<olivier.dugeon at orange.com> wrote:
> Hello Renato,
>
> Very nice support. As mention before, unfortunately I could not attend the
> meeting today, so here it is my remarks and questions:
>
> First I fully support your proposal. I'm very happy to see Yang / Netconf /
> Restconf support coming for FRR and I'm very impatient to test it
> Regarding the amount of work, I'm ready to help (at least for my patches)

Hi Olivier,

Thanks, any help will be welcomed :)

> Regarding sysrepo or ConfD, I have no particular opinion
> Regarding transactional CLI, I think this feature must become the default
> one with 'commit' command that check the syntax. In addition, when you
> preform some CLI configuration, it is sometimes preferable to have all the
> modification apply at once instead of applying step by step, just to avoid
> bad effect between the different modifications

I agree the transactional CLI should be enabled by default, but only
after we convert all configuration commands to the new northbound
model. The problem here is that commands not converted to the new
northbound model change the running configuration directly. My concern
is that things can get confusing if some commands change the candidate
configuration and others change the running configuration. Once we
convert everything we won't have this problem anymore. When the
transaction-based mode is not used, all configuration commands are
followed by an implicit "commit" (i.e. one transaction per change).

> Concerning the show command, I think that you could collect information
> through a simple HTTP GET with Restconf. It is working like that in
> OpenDayLight for example

Fetching the whole configuration using a simple HTTP GET should be
possible when using the ConfD northbound plugin. However I can't test
this because RESTCONF support isn't available in ConfD Basic (the free
version).

In the future this might also be possible using the Sysrepo northbound
plugin if support for RESTCONF is integrated in Netopeer2.

> Last question: do you know if there is some 'yang tools' available with
> lbyang in order to help us building new CLI / features .i.e. generating
> automatically structure skeleton ? I'm referring to the OpenDayLight project
> where you start first by writing a yang model which then produce Java Class
> automatically through the yang tools provided by OpenDayLight. For example,
> in FRR, such tools could automatically generate 'C' structure in *.h file
> for parser and serializer of protocol, CLI ...

Good question. libyang seems to be very minimalistic by design and
they don't provide tools like that. But the good news is that we can
use libyang to create our own tools very easily. For example, I wrote
a tool called 'gen_northbound_callbacks' which takes a YANG module as
input and generates skeleton callbacks [1] for this module. This saves
a lot of time because the programmer only needs to worry about
implementing real code, all the boilerplate will be there already. The
possibility to auto-generate code is one of the advantages of using
YANG and data modeling languages in general.

Thanks for your feedback!

[1] https://github.com/opensourcerouting/frr/blob/cb0560ade9/ripd/rip_northbound.c

-- 
Renato Westphal