Hi,
We have a question with respect to YANG models using features. Assume that a
part of the model is defined under a feature and that this feature-dependent
part defines a leaf as mandatory.
module servers {
namespace "http://www.example.com/servers";;
prefix servers;
import ietf-inet-types {
prefix inet;
}
revision 2018-03-01 {
description
"Initial version.";
}
feature test-feature {
description "testing feature";
}
container servers {
list server {
key name;
max-elements 64;
leaf name {
type string;
}
leaf ip {
type inet:ip-address;
mandatory true;
}
leaf port {
type inet:port-number;
mandatory true;
}
leaf only-if-feature {
if-feature test-feature;
type string;
mandatory true;
}
}
}
}
Now assume that we have a device that implements the model step-wise by first
not supporting this feature and in a sub-sequent release by supporting this
feature (and uses a persistent running datastore). The question arising now is
how to deal with this mandatory leaf? Normally this can only be configured by
a client, meaning that without any "help", the NC server will not be able to
startup with the data contained in the device's persistent datastore unless a
value is set for the mandatory leaf that now becomes available as a result of
supporting the feature.
When modeling as follows it seems the NC server can start with the model
supporting the feature that was not supported before:
module servers {
namespace "http://www.example.com/servers";;
prefix servers;
import ietf-inet-types {
prefix inet;
}
revision 2018-03-01 {
description
"Initial version.";
}
feature test-feature {
description "testing feature";
}
container servers {
list server {
key name;
max-elements 64;
leaf name {
type string;
}
leaf ip {
type inet:ip-address;
mandatory true;
}
leaf port {
type inet:port-number;
mandatory true;
}
container only-if-feature {
presence "see if this helps";
if-feature test-feature;
leaf only-if-feature {
type string;
mandatory true;
}
}
}
}
}
Are recommendations or guidelines in place to deal with this?
Regards, Bart
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