Customizing the ZenPack Installation Process

There are some circumstances where we need to perform certain tasks in our ZenPack the moment it is installed. We can achieve this using Python by placing this logic inside the ZenPack's top directory's __init__.py file. When creating a fresh ZenPack using zenpacklib, this __init__.py file will contain the following contents:

from . import zenpacklib

CFG = zenpacklib.load_yaml()

To add custom functionality that gets executed when the ZenPack is installed, we need to extend the install method of the ZenPack class. Below the original code, we can proceed to do so:

class ZenPack(schema.ZenPack):
    def install(self, app):
        # Our custom logic here

        super(ZenPack, self).install(app)

No other imports are necessary. Notice the last line of the install method, this is where the ZenPack gets installed.

For the purpuse of giving an example, Let's say that our ZenPack creates two new zProperties, one property to store an API key, and the other one to store a URL. Moreover let's say that we obtain these values from somewhere and we want to assign them automatically to the properties upon the installation of the ZenPack.

These two new properties are defined in zenpack.yaml:

name: ZenPacks.aalvarez.MyZenPack

zProperties:
  zMyApiUrl:
    category: MyApi
    type: string

  zMyApiKey:
    category: MyApi
    type: string

Then we add the logic to the __init__.py file:

class ZenPack(schema.ZenPack):
    def install(self, app):
        self._set_api_config()
        super(ZenPack, self).install(app)

    def _set_api_config(self):
        # Let's assume the values are stored in a text file
        with open('api_conf') as f:
          api_url = f.readline()
          api_key = f.readline()

          try:
              self.dmd.Devices.setZenProperty('zMyApiUrl', api_url)
              self.dmd.Devices.setZenProperty('zMyApiKey', api_key)
          except Exception as e:
              pass

          f.close()

When the ZenPack is installed, the above code will be executed and the zProperties will be assigned the values obtained from the text file. This is just one of the many possible tasks that you might need to perform upon installation.

Another good example is the appending of additional modeler plugins to certain device class. This I will try to cover in a future post.