NSO yang leafref device-group

[AndyK1]

I'm attempting to create my first service template but have issues when referencing device-groups in my yang file.

user@ncs(config)# L2-BRIDGE TEST device-group LEAF-SWITCHES vlan 10 vni 10002

user@ncs(config-L2-BRIDGE-TEST)# commit dry-run outformat native

Aborted: L2-BRIDGE-template.xml:5 The node '/ncs:devices/device{LEAF-SWITCHES}' was not created. An explicit tag 'merge' or 'create' is needed.

The device-group LEAF-SWITCHES exists within NSO and contains some switches.

    leaf-list device-group {

      type leafref {

        path "/ncs:devices/ncs:device-group/ncs:name";

      }

    }

If I replace 'device-group' with 'device' I am able to run the service against individual nodes.  

Any pointers would be appreciated.

Thanks

[ramkraja]

Hi,
> Aborted: L2-BRIDGE-template.xml:5 The node '/ncs:devices/device{LEAF-SWITCHES}' was not created. An explicit tag 'merge' or 'create' is needed.

This error message means that you should explicitly use the tag "merge" or "create" in your service template, if you want to create a new device. I'm assuming you are not creating a new device, but trying to refer to an existing device in a device-group. Could you show your yang model and the service template?

Thanks,
Ram

[AndyK1]

Correct, I am not trying to create a new device as they are existing within the device-group.  My goal for this initial test is to deploy the service template to all the devices within the device-group.  

<config-template xmlns="http://tail-f.com/ns/config/1.0"
                 servicepoint="L2-BRIDGE">
  <devices xmlns="http://tail-f.com/ns/ncs">
  <device>
    <name>{/device-group}</name>
    <config>
      <vlan xmlns="http://tail-f.com/ned/cisco-nx">
        <vlan-list>
          <id>{/vlan}</id>
          <name>{/customer-name}</name>
          <vn-segment>{/vni}</vn-segment>
        </vlan-list>
      </vlan>
      <evpn xmlns="http://tail-f.com/ned/cisco-nx">
        <vni>
          <id>{/vni}</id>
          <l2/>
          <rd>auto</rd>
          <route-target>
            <method>import</method>
            <rt>auto</rt>
          </route-target>
          <route-target>
            <method>export</method>
            <rt>auto</rt>
          </route-target>
        </vni>
      </evpn>
      <interface xmlns="http://tail-f.com/ned/cisco-nx">
        <nve>
          <name>1</name>
          <member>
            <vni>
              <id>{/vni}</id>
              <suppress-arp/>
              <ingress-replication>
                <protocol>
                  <bgp/>
                </protocol>
              </ingress-replication>
            </vni>
          </member>
        </nve>
        <port-channel>
          <name>200</name>
          <switchport>
            <trunk>
              <allowed>
                <vlan>
                  <ids>{/vlan}</ids>
                </vlan>
              </allowed>
            </trunk>
          </switchport>
        </port-channel>
      </interface>
    </config>
  </device>
 </devices>
</config-template>

module L2-BRIDGE {
  namespace "http://com/example/L2BRIDGE";
  prefix L2-BRIDGE;

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

  list L2-BRIDGE {
    key customer-name;

    uses ncs:service-data;
    ncs:servicepoint "L2-BRIDGE";

    leaf customer-name {
      type string;
    }

    leaf-list device-group {
      type leafref {
        path "/ncs:devices/ncs:device-group/ncs:name";
      }
    }
    leaf vlan {
      mandatory true;
      type uint16;
    }
      
    leaf vni {
      mandatory true;
      type uint16;
    }
  }
}

Thanks!

[ramkraja]

Hello,
Ok, the problem is here:
-----------------------



{/device-group}

-----------------------

If you do "commit dry-run | debug template", you can see that the expression {/device-group} evaluates to the single device-group name, and that is given as the name of the device to the template above. What you need is to get the devices inside that device-group.
In this case, you can use 'deref' to dereference the leafref in your service model. So, you can use something like
-----------------------



{deref(/device-group)/../member}

-----------------------
(/devices/device-group/member is the flattened list of all members of a device-group. You need this, instead of devices/device-group/device-name, because device-groups can be nested).

However, the "device-group" in your service is itself a leaf-list - which means there can be multiple device-groups configured in your service model. Then the above deref won't be fully correct, since it only works for the first leaf-list entry. Now you need to iterate through the items in your service model's leaf-list, which you can do like this:
-----------------------




{deref(.)/../member}
...
...



-----------------------

Try something like this!

/Ram

[ramkraja · Accepted solution]

Hmm.. Stupid thing ate my xml tags..

Trying again:

-------------------------------

Hello,

Ok, the problem is here:

  <devices xmlns="http://tail-f.com/ns/ncs">
  <device>
    <name>{/device-group}</name> 

If you do "commit dry-run | debug template", you can see that the expression {/device-group} evaluates to the single device-group name, and that is given as the name of the device to the template above. What you need is to get the devices inside that device-group.

In this case, you can use 'deref' to dereference the leafref in your service model. So, you can use something like

  <devices xmlns="http://tail-f.com/ns/ncs">
  <device>
    <name>{deref(/device-group)/../member}</name>

(/devices/device-group/member is the flattened list of all members of a device-group. You need this, instead of devices/device-group/device-name, because device-groups can be nested).

However, the "device-group" in your service is itself a leaf-list - which means there can be multiple device-groups configured in your service model. Then the above deref won't be fully correct, since it only works for the first leaf-list entry. Now you need to iterate through the items in your service model's leaf-list, which you can do like this:

<devices xmlns="http://tail-f.com/ns/ncs">
  <?foreach {/device-group}?>
  <device>
    <name>{deref(.)/../member}</name>
    ...
    ...
  </device>
  <?end?>
</devices>

Try something like this!

/Ram

-------------------------------

[AndyK1]

Thanks Ram, that worked a charm!