Post-modification call back in python

[yale.prince@leidos.com]

Hi all,

we are trying to create a services that configures an SVI via python/template and then in python change the state of the interface to shut or no shut depending on an admin_state field we have added to the yang model of the services.

issue we are having is that we cannot update the state of the interface IE shut or no shut via python as its says the vlan interface is not yet in the CDB

>>> device.config.nx__interface.Vlan["3001"].shutdown.exists()

True

>>> 

>>> t = m.start_write_trans()

>>> root = maagic.get_root(t)

>>> device = root.devices.device['N7K-VDC-1']

>>> 

>>> device.config.nx__interface.Vlan["3001"].shutdown.exists()

True

>>> 

>>> device.config.nx__interface.Vlan["3001"].shutdown.delete()

>>> device.config.nx__interface.Vlan["3001"].shutdown.exists()

False

>>> 

>>> t.apply()

>>> 

how can we work around this issue without making an additional call 

Thanks

Regards

Yale

[vleijon]

Can you elaborate on the issue - I am not quite sure if I follow what it is you'd like to work that doesn't?

Also, why are you trying to use a post-modification call-back in the first place instead of doing this from your service code?

[yale.prince@leidos.com]

the services creates the vlan interface via a template, we did then try to set the interfaces state (shut /no shut) via python but we get this error

  File "/opt/nso_custom_python/nso_utils/config_modify_functions.py", line 29, in set_admin_state
    device.config.nx__interface.Vlan[vlan_name].shutdown.delete()
  File "/opt/ncs/ncs-4.7.2.1/src/ncs/pyapi/ncs/maagic.py", line 1076, in __getitem__
    raise KeyError('%s not in %s' % (keystr, self._path))
KeyError: '{3001} not in /ncs:devices/device{N7K-VDC-1}/config/nx:interface/Vlan'

thus we thought we should look at post-mod

[vleijon]

Okay. So, how do you apply the template and where do you have the python code? Perhaps you have a code snippet or something like that? It seems like you ought to be able to do this as long as you are in the same transaction and just after the template application.

[yale.prince@leidos.com]

    @service.create
    def cb_create(self, tctx, root, service, proplist):
        
        # set all require variables here e.g. ...
        vars.add('device', 'foo')
        vars.add('vrf_name', 'bar')

        # apply the template 
        template = ncs.template.Template(service)
        template.apply(template_name, vars)

        # break into python
        m = maapi.Maapi()
        m.start_user_session('admin','foobar')
        t = m.start_write_trans()
        root = maagic.get_root(t)
        device = root.devices.device['N7K-VDC-1']
        device.config.nx__interface.Vlan["3001"].shutdown.create()
        t.apply()

[vleijon]

So the problem here is that you create a new transaction, which does not run inside of the service transaction. In general you almost never want to start a transaction from inside your create code.

Instead you want to re-use the handle you already have available to you. You have an argument named 'root' which is a maagic object that you can use to make your changes, use that directly instead of creating your own root object and things ought to work.