NSO data-kicker monitor within interface

[mikeg22]

I can successfully configure a data-kicker to monitor any changes within an interface:

admin@ncs(config)# kickers data-kicker mykicker monitor /devices/device[name='c0']/config/interface
admin@ncs(config-data-kicker-mykicker)# commit
Commit complete.

but trying to limit the kicker scope further within the interface fails:

admin@ncs(config)# kickers data-kicker mykicker monitor /devices/device[name='c0']/config/interface/switchport
admin@ncs(config-data-kicker-mykicker)# commit
Aborted: 'kickers data-kicker mykicker monitor': invalid path.

I tried examining the YANG to get some clues, but was surprised to discover "switchport" and "vlan" leafs don't exist:

mike@Mikes-MacBook-Pro yang % pwd
/Users/mike/ncs/install-5.7.11/src/ncs/yang

mike@Mikes-MacBook-Pro yang % grep -r --include="*.yang" "switchport" *
mike@Mikes-MacBook-Pro yang %
mike@Mikes-MacBook-Pro yang % grep -r --include="*.yang" "vlan" *
tailf-cli-extensions.yang: vlan 1,3,10-20,30,32,300-310
mike@Mikes-MacBook-Pro yang %

How can I create a data-kicker monitor for all interface switchport access vlans on a device?

[Marcel Zehnder]

Hi

Looks like your xpath is invalid because the interface type is missing, try this:
kickers data-kicker mykicker monitor /devices/device[name='c0']/config/interface/*/switchport

Or if you know the type (for example GigabitEthernet):
kickers data-kicker mykicker monitor /devices/device[name='c0']/config/interface/GigabitEthernet/switchport

HTH

[mikeg22]

Hello Marcel,

Thank you for the suggestions. The first one seems like an intuitive solution, but gives the same result:

admin@ncs(config)# kickers data-kicker mykicker monitor /devices/device[name='c0']/config/interface/*/switchport
admin@ncs(config-data-kicker-mykicker)# commit
Aborted: 'kickers data-kicker mykicker monitor': internal error

The second one worked for me:

admin@ncs(config-data-kicker-mykicker)# kickers data-kicker mykicker monitor /devices/device[name='c0']/config/interface/GigabitEthernet/switchport/access/vlan
admin@ncs(config-data-kicker-mykicker)# commit
Commit complete.

I'm thrilled to have your solution and would also like to better understand why my initial monitor (and your wildcard version) do not work. It seems like NSO has some "special" way of processing interfaces.

Best regards,
Mike

[Marcel Zehnder]

Actually I don't have to much experience with kickers and need to dig in myself. I hope one of the NSO cracks in the forum can explain this.

[Marcel Zehnder]

I'm thrilled to have your solution and would also like to better understand why my initial monitor (and your wildcard version) do not work. It seems like NSO has some "special" way of processing interfaces.

Your example did not work just because it's an invalid xpath - you must specify this intermediate node in some way - I don't know why my first example is not working - from my point of view it should, cause it's a valid path. However, can you try this one as well:

kickers data-kicker mykicker monitor /devices/device[name='c0']/config/interface//switchport

[snovello]

Hi,
The monitor leaf in a kicker is not a generic xpath. So /*/ or // will not work. It is an identityref, so you just give a the nodes to traverse and conditions like [key_name=’key_value’]. See https://datatracker.ietf.org/doc/html/rfc7950#section-9.10

[Marcel Zehnder]

Thanks for the clarification.

[ramkraja · Accepted solution]

The YANG type is in fact an instance-identifier, and not an identityref.

But the actual type used in our model is the "node-instance-identifier". From tailf-kickers.yang

      leaf monitor {
        type tailf:node-instance-identifier;
        mandatory true;
        ...
      }

And "node-instance-identifier" is essentially the same as the yang builtin "instance-identifier", except that predicates for keys are optional. That is why this expression above works:

/devices/device[name='c0']/config/interface/GigabitEthernet/switchport/access/vlan

Here, the key for the list GigabitEthernet is not specified - which means it will monitor all instances of the list.

Other than keys, there is no way to skip some nodes in the path or use wildcards for path nodes etc.

[tohagber]

As per stated in the tailf-kicker.yang module, the "monitor" leaf takes a value that is "like a yang instance-identifier but list nodes may be specified without keys, omitting the key predicate will be interpreted as a key wild-card.

leaf monitor {
  type tailf:node-instance-identifier;
  mandatory true;
  tailf:validate data-kicker {
    tailf:internal;
    tailf:dependency ".";
    tailf:dependency "../variable";
  }
  description
   "If a node that matches the value of this leaf is changed,
   the 'trigger-expr' expression is evaluated, and the
   'trigger-type' is used to determine if the kicker triggers
   or not.

   The value of this leaf is like an instance-identifier, but
   a list may be specified without any keys. This is treated like
   a wildcard that matches all entries in the list.";
}

As far as i can read from ABNF grammar a yang instance-identifier is not allowed to use the "//" operator. So you need a fully specified path. Which is what you tried in the second one that worked.

[mikeg22]

Many thanks to Marcel for demonstrating a way to get to the vlan node and you all for clarifying the differences between a kicker monitor and an Xpath. I now have a better understanding of the constraints involved.

Best regards,

Mike