+from .client import watcher
+from .delta import get_entity_delta
+
+
+class ModelEntity(object):
+ """An object in the Model tree"""
+
+ def __init__(self, data, model):
+ """Initialize a new entity
+
+ :param data: dict of data from a watcher delta
+ :param model: The model instance in whose object tree this
+ entity resides
+
+ """
+ self.data = data
+ self.model = model
+
+ def __getattr__(self, name):
+ return self.data[name]
+
+
class Model(object):
+ def __init__(self, connection):
+ """Instantiate a new connected Model.
+
+ :param connection: `juju.client.connection.Connection` instance
+
+ """
+ self.connection = connection
+ self.observers = set()
+ self.state = dict()
+
+ def add_observer(self, callable_):
+ """Register an "on-model-change" callback
+
+ Once a watch is started (Model.watch() is called), ``callable_``
+ will be called each time the model changes. callable_ should
+ accept the following positional arguments:
+
+ delta - An instance of :class:`juju.delta.EntityDelta`
+ containing the raw delta data recv'd from the Juju
+ websocket.
+
+ old_obj - If the delta modifies an existing object in the model,
+ old_obj will be a copy of that object, as it was before the
+ delta was applied. Will be None if the delta creates a new
+ entity in the model.
+
+ new_obj - A copy of the new or updated object, after the delta
+ is applied. Will be None if the delta removes an entity
+ from the model.
+
+ model - The :class:`Model` itself.
+
+ """
+ self.observers.add(callable_)
+
+ async def watch(self):
+ """Start an asynchronous watch against this model.
+
+ See :meth:`add_observer` to register an onchange callback.
+
+ """
+ allwatcher = watcher.AllWatcher()
+ allwatcher.connect(self.connection)
+ while True:
+ results = await allwatcher.Next()
+ for delta in results.deltas:
+ delta = get_entity_delta(delta)
+ old_obj, new_obj = self._apply_delta(delta)
+ self._notify_observers(delta, old_obj, new_obj)
+
+ def _apply_delta(self, delta):
+ """Apply delta to our model state and return the a copy of the
+ affected object as it was before and after the update, e.g.:
+
+ old_obj, new_obj = self._apply_delta(delta)
+
+ old_obj may be None if the delta is for the creation of a new object,
+ e.g. a new application or unit is deployed.
+
+ new_obj may be if no object was created or updated, or if an object
+ was deleted as a result of the delta being applied.
+
+ """
+ old_obj, new_obj = None, None
+
+ if (delta.entity in self.state and
+ delta.get_id() in self.state[delta.entity]):
+ old_obj = self.state[delta.entity][delta.get_id()]
+ if delta.type == 'remove':
+ del self.state[delta.entity][delta.get_id()]
+ return old_obj, new_obj
+
+ new_obj = self.state.setdefault(delta.entity, {})[delta.get_id()] = (
+ self._create_model_entity(delta))
+
+ return old_obj, new_obj
+
+ def _create_model_entity(self, delta):
+ """Return an object instance representing the entity created or
+ updated by ``delta``
+
+ """
+ entity_class = delta.get_entity_class()
+ return entity_class(delta.data, self)
+
+ def _notify_observers(self, delta, old_obj, new_obj):
+ """Call observing callbacks, notifying them of a change in model state
+
+ :param delta: The raw change from the watcher
+ (:class:`juju.client.overrides.Delta`)
+ :param old_obj: The object in the model that this delta updates.
+ May be None.
+ :param new_obj: The object in the model that is created or updated
+ by applying this delta.
+
+ """
+ for o in self.observers:
+ o(delta, old_obj, new_obj, self)
+
def add_machine(
self, spec=None, constraints=None, disks=None, series=None,
count=1):
projects / osm / N2VC.git / blobdiff