Models¶
A Juju controller provides websocket endpoints for each of its models. In order to do anything useful with a model, the juju lib must connect to one of these endpoints. There are several ways to do this.
For api docs, see juju.model.Model.
Connecting to the Current Model¶
Connect to the currently active Juju model (the one returned by juju switch). This only works if you have the Juju CLI client installed.
from juju.model import Model
model = Model()
await model.connect_current()
Connecting to a Named Model¶
Connect to a model by name, using the same format as that returned from the juju switch command. The accepted format is ‘[controller:][user/]model’. This only works if you have the Juju CLI client installed.
# $ juju switch
# juju-2.0.1:admin/libjuju
from juju.model import Model
model = Model()
await model.connect_model('juju-2.0.1:admin/libjuju')
Connecting with Username/Password Authentication¶
The most flexible, but also most verbose, way to connect is using the API endpoint url and credentials directly. This method does NOT require the Juju CLI client to be installed.
from juju.model import Model
model = Model()
controller_endpoint = '10.0.4.171:17070'
model_uuid = 'e8399ac7-078c-4817-8e5e-32316d55b083'
username = 'admin'
password = 'f53f08cfc32a2e257fe5393271d89d62'
# Left out for brevity, but if you have a cert string you should pass it in.
# You can copy the cert from the output of The `juju show-controller`
# command.
cacert = None
await model.connect(
controller_endpoint,
model_uuid,
username,
password,
cacert,
)
Connecting with Macaroon Authentication¶
To connect to a shared model, or a model an a shared controller, you’ll need to use macaroon authentication. The simplest example is shown below, and uses already-discharged macaroons from the local filesystem. This will work if you have the Juju CLI installed.
Note
The library does not yet contain support for fetching and discharging macaroons. Until it does, if you want to use macaroon auth, you’ll need to supply already-discharged macaroons yourself.
from juju.client.connection import get_macaroons()
from juju.model import Model
model = Model()
controller_endpoint = '10.0.4.171:17070'
model_uuid = 'e8399ac7-078c-4817-8e5e-32316d55b083'
username = None
password = None
cacert = None
macaroons = get_macaroons()
await model.connect(
controller_endpoint,
model_uuid,
username,
password,
cacert,
macaroons,
)
Creating and Destroying a Model¶
Example of creating a new model and then destroying it. See
juju.controller.Controller.add_model() and
juju.controller.Controller.destroy_model() for more info.
from juju.controller import Controller
controller = Controller()
await controller.connect_current()
# Create our new model
model = await controller.add_model(
'mymodel', # name of your new model
)
# Do stuff with our model...
# Destroy the model
await model.disconnect()
await controller.destroy_model(model.info.uuid)
model = None
Adding Machines and Containers¶
To add a machine or container, connect to a model and then call its
add_machine() method. A
Machine instance is returned. The machine id
can be used to deploy a charm to a specific machine or container.
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
model. The easiest way to do this is by creating a
juju.model.ModelObserver subclass.
from juju.model import Model, ModelObserver
class MyModelObserver(ModelObserver):
async def on_change(self, delta, old, new, model):
# The raw change data (dict) from the websocket.
print(delta.data)
# The entity type (str) affected by this change.
# One of ('action', 'application', 'annotation', 'machine',
# 'unit', 'relation')
print(delta.entity)
# The type (str) of change.
# One of ('add', 'change', 'remove')
print(delta.type)
# The 'old' and 'new' parameters are juju.model.ModelEntity
# instances which represent an entity in the model both before
# this change was applied (old) and after (new).
# If an entity is being added to the model, the 'old' param
# will be None.
if delta.type == 'add':
assert(old is None)
# If an entity is being removed from the model, the 'new' param
# will be None.
if delta.type == 'remove':
assert(new is None)
# The 'old' and 'new' parameters, when not None, will be instances
# of a juju.model.ModelEntity subclass. The type of the subclass
# depends on the value of 'delta.entity', for example:
#
# delta.entity type
# ------------ ----
# 'action' -> juju.action.Action
# 'application' -> juju.application.Application
# 'annotation' -> juju.annotation.Annotation
# 'machine' -> juju.machine.Machine
# 'unit' -> juju.unit.Unit
# 'relation' -> juju.relation.Relation
# Finally, the 'model' parameter is a reference to the
# juju.model.Model instance to which this observer is attached.
print(id(model))
model = Model()
await model.connect_current()
model.add_observer(MyModelObserver())
Every change in the model will result in a call to the on_change() method of your observer(s).
To target your code more precisely, define method names that correspond to the entity and type of change that you wish to handle.
from juju.model import Model, ModelObserver
class MyModelObserver(ModelObserver):
async def on_application_change(self, delta, old, new, model):
# Both 'old' and 'new' params will be instances of
# juju.application.Application
pass
async def on_unit_remove(self, delta, old, new, model):
# Since a unit is being removed, the 'new' param will always
# be None in this handler. The 'old' param will be an instance
# of juju.unit.Unit - the state of the unit before it was removed.
pass
async def on_machine_add(self, delta, old, new, model):
# Since a machine is being added, the 'old' param will always be
# None in this handler. The 'new' param will be an instance of
# juju.machine.Machine.
pass
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 juju.model.ModelEntity object can be observed directly by
registering callbacks on the object itself.
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)