model = None
+Adding Machines and Containers
+------------------------------
+To add a machine or container, connect to a model and then call its
+:meth:`~juju.model.Model.add_machine` method. A
+:class:`~juju.machine.Machine` instance is returned. The machine id
+can be used to deploy a charm to a specific machine or container.
+
+.. code:: python
+
+ from juju.model import Model
+
+ MB = 1
+ GB = 1024
+
+
+ model = Model()
+ await model.connect_current()
+
+ # add a new default machine
+ machine1 = await model.add_machine()
+
+ # add a machine with constraints, disks, and series specified
+ machine2 = await model.add_machine(
+ constraints={
+ 'mem': 256 * MB,
+ },
+ disks=[{
+ 'pool': 'rootfs',
+ 'size': 10 * GB,
+ 'count': 1,
+ }],
+ series='xenial',
+ )
+
+ # add a lxd container to machine2
+ machine3 = await model.add_machine(
+ 'lxd:{}'.format(machine2.id))
+
+ # deploy charm to the lxd container
+ application = await model.deploy(
+ 'ubuntu-10',
+ application_name='ubuntu',
+ series='xenial',
+ channel='stable',
+ to=machine3.id
+ )
+
+ # remove application
+ await application.remove()
+
+ # destroy machines - note that machine3 must be destroyed before machine2
+ # since it's a container on machine2
+ await machine3.destroy(force=True)
+ await machine2.destroy(force=True)
+ await machine1.destroy(force=True)
+
+
Reacting to Changes in a Model
------------------------------
To watch for and respond to changes in a model, register an observer with the
async def on_change(self, delta, old, new, model):
# The catch-all handler - will be called whenever a more
# specific handler method is not defined.
+
+
+Any :class:`juju.model.ModelEntity` object can be observed directly by
+registering callbacks on the object itself.
+
+.. code:: python
+
+ import logging
+
+ async def on_app_change(delta, old, new, model):
+ logging.debug('App changed: %r', new)
+
+ async def on_app_remove(delta, old, new, model):
+ logging.debug('App removed: %r', old)
+
+ ubuntu_app = await model.deploy(
+ 'ubuntu',
+ application_name='ubuntu',
+ series='trusty',
+ channel='stable',
+ )
+ ubuntu_app.on_change(on_app_change)
+ ubuntu_app.on_remove(on_app_remove)