Yang leafref question

[rjbotham]

Hi All,

I wanted to as a basic question re yang leaf refs as i'm just starting with NSO

I have a very simple model, however ,the part i'm struggling to understand is this section below defining  the device leaf

The module imports tailf-ncs and so naturally I went looking in that module for /devices/device/name

However when I open tailf-ncs.yang it also imports many other models and I ended up 'down a rabbit hole'

I'm trying to learn so that I understand all parts of the model so would appreciate some assistance and a 'steer' if i'm mis- understanding this and where is should look to follow and understand the leaf ref

Thanks

Rich

leaf device {
      type leafref {
        path "/ncs:devices/ncs:device/ncs:name";
      }
    }

Model

module access {
  namespace "http://com/example/access";
  prefix access;

  import ietf-inet-types {
    prefix inet;
  }
  import tailf-ncs {
    prefix ncs;
  }

  list access {
    key customer-name;

    uses ncs:service-data;
    ncs:servicepoint "access";

    leaf customer-name {
      type string;
    }


    /*
    1 - We import tailf-ncs.yang and give that a prefix of ncs
    Home@Richs-MacBook-Pro:~/Documents/Programming/nso5.7/src/ncs/yang$ grep -Ril 'list devices' ./
  .//tailf-ncs-plan.yang
  .//tailf-ncs-webui.yang
  .//tailf-ncs-services.yang
  .//tailf-ncs-devices.yang
    
    */
    leaf device {
      type leafref {
        path "/ncs:devices/ncs:device/ncs:name";
      }
    }
    
    leaf vlan {
     mandatory true;
     type uint16;
    }
   
    leaf access-interface {
     mandatory true;
     type string; 
    }

    leaf trunk-interface {
     mandatory true;
     type string; 
    }
  }
}

[tcragg1 · Accepted solution]

A leafref is a pointer to another part of the model. The leafref selects the set of leaf instances at the path listed at the "path" substatement. In this case, a leafref pointing to "/ncs:devices/ncs:device/ncs:name" will return the set of all devices configured within NSO. If you configure an instance of your service in NCS CLI and attempt an auto-complete after "device", you will see that the available options for the device leaf are the set of devices configured within NSO.

[rjbotham]

Hello tcragg1,

Many thanks for the explanation

So does this actually refer to the entries in the CDB files, and I presume, that for any given service, a complete list devices would be available and not just the devices associated with that service ? 

import tailf-ncs {
    prefix ncs;
  }

[tcragg1]

---

@rjbotham wrote:

Hello tcragg1,

Many thanks for the explanation

So does this actually refer to the entries in the CDB files, and I presume, that for any given service, a complete list devices would be available and not just the devices associated with that service ? 

---

That's correct. If you use the same leafref in multiple services, they will each have access to the full list of devices configured in NSO.