# Copyright 2019 Canonical Ltd.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Base objects for the Charm, events and metadata."""
from __future__ import annotations
import dataclasses
import enum
import logging
import pathlib
import warnings
from typing import (
TYPE_CHECKING,
Any,
ClassVar,
List,
Literal,
Mapping,
NoReturn,
Optional,
TextIO,
TypedDict,
TypeVar,
cast,
)
from . import model
from ._private import yaml
from .framework import (
EventBase,
EventSource,
Framework,
Handle,
LifecycleEvent,
Object,
ObjectEvents,
)
if TYPE_CHECKING:
from typing_extensions import Required
_Scopes = Literal['global', 'container']
_RelationMetaDict = TypedDict(
'_RelationMetaDict',
{'interface': Required[str], 'limit': int, 'optional': bool, 'scope': _Scopes},
total=False,
)
_MultipleRange = TypedDict('_MultipleRange', {'range': str})
_StorageMetaDict = TypedDict(
'_StorageMetaDict',
{
'type': Required[str],
'description': str,
'shared': bool,
'read-only': bool,
'minimum-size': str,
'location': str,
'multiple-range': str,
'multiple': _MultipleRange,
},
total=False,
)
_ResourceMetaDict = TypedDict(
'_ResourceMetaDict',
{'type': Required[str], 'filename': str, 'description': str},
total=False,
)
_MountDict = TypedDict('_MountDict', {'storage': Required[str], 'location': str}, total=False)
class _ContainerBaseDict(TypedDict):
name: str
channel: str
architectures: list[str]
logger = logging.getLogger(__name__)
[docs]
class HookEvent(EventBase):
"""Events raised by Juju to progress a charm's lifecycle.
Hooks are callback methods of a charm class (a subclass of
:class:`CharmBase`) that are invoked in response to events raised
by Juju. These callback methods are the means by which a charm
governs the lifecycle of its application.
The :class:`HookEvent` class is the base of a type hierarchy of events
related to the charm's lifecycle.
:class:`HookEvent` subtypes are grouped into the following categories
- Core lifecycle events
- Relation events
- Storage events
- Metric events
"""
[docs]
class ActionEvent(EventBase):
"""Events raised by Juju when an administrator invokes a Juju Action.
This class is the data type of events triggered when an administrator
invokes a Juju Action. Callbacks bound to these events may be used
for responding to the administrator's Juju Action request.
To read the parameters for the action, see the instance variable
:attr:`~ops.ActionEvent.params`.
To respond with the result of the action, call
:meth:`~ops.ActionEvent.set_results`. To add progress messages that are
visible as the action is progressing use :meth:`~ops.ActionEvent.log`.
"""
id: str = ''
"""The Juju ID of the action invocation."""
params: dict[str, Any]
"""The parameters passed to the action."""
def __init__(self, handle: Handle, id: str | None = None):
super().__init__(handle)
self.id = id # type: ignore (for backwards compatibility)
[docs]
def defer(self) -> NoReturn:
"""Action events are not deferrable like other events.
This is because an action runs synchronously and the administrator
is waiting for the result.
Raises:
RuntimeError: always.
"""
raise RuntimeError('cannot defer action events')
[docs]
def restore(self, snapshot: dict[str, Any]):
"""Used by the framework to record the action.
Not meant to be called directly by charm code.
"""
self.id = cast('str', snapshot['id'])
# Params are loaded at restore rather than __init__ because
# the model is not available in __init__.
self.params = self.framework.model._backend.action_get()
[docs]
def snapshot(self) -> dict[str, Any]:
"""Used by the framework to serialize the event to disk.
Not meant to be called by charm code.
"""
return {'id': self.id}
[docs]
def set_results(self, results: dict[str, Any]):
"""Report the result of the action.
Juju eventually only accepts a str:str mapping, so we will attempt
to flatten any more complex data structure like so::
>>> {'a': 'b'} # becomes: 'a'='b'
>>> {'a': {'b': 'c'}} # becomes: 'a.b'='c'
>>> {'a': {'b': 'c', 'd': 'e'}} # becomes: 'a.b'='c', 'a.d' = 'e'
>>> {'a.b': 'c', 'a.d': 'e'} # equivalent to previous
Note that duplicate keys are not allowed, so this is invalid::
>>> {'a': {'b': 'c'}, 'a.b': 'c'}
Note that the resulting keys must start and end with lowercase
alphanumeric, and can only contain lowercase alphanumeric, hyphens
and periods.
Because results are passed to Juju using the command line, the maximum
size is around 100KB. However, actions results are designed to be
small: a few key-value pairs shown in the Juju CLI. If larger content
is needed, store it in a file and use something like ``juju scp``.
If any exceptions occur whilst the action is being handled, juju will
gather any stdout/stderr data (and the return code) and inject them into the
results object. Thus, the results object might contain the following keys,
additionally to those specified by the charm code:
- Stdout
- Stderr
- Stdout-encoding
- Stderr-encoding
- ReturnCode
Args:
results: The result of the action as a Dict
Raises:
ModelError: if a reserved key is used.
ValueError: if ``results`` has a mix of dotted/non-dotted keys that expand out to
result in duplicate keys, for example: :code:`{'a': {'b': 1}, 'a.b': 2}`. Also
raised if a dict is passed with a key that fails to meet the format requirements.
OSError: if extremely large (>100KB) results are provided.
"""
self.framework.model._backend.action_set(results)
[docs]
def log(self, message: str):
"""Send a message that a user will see while the action is running.
Args:
message: The message for the user.
"""
self.framework.model._backend.action_log(message)
[docs]
def fail(self, message: str = ''):
"""Report that this action has failed.
Args:
message: Optional message to record why it has failed.
"""
self.framework.model._backend.action_fail(message)
[docs]
def load_params(
self,
cls: type[_T],
*args: Any,
errors: Literal['raise', 'fail'] = 'raise',
**kwargs: Any,
) -> _T:
"""Load the action parameters into an instance of an action class.
The raw Juju action parameters are passed to the action class's
``__init__`` method as keyword arguments, with dashes in names
converted to underscores.
For dataclasses and Pydantic ``BaseModel`` subclasses, only fields in
the Juju action parameters that have a matching field in the class are
passed as arguments.
For example::
class BackupParams(pydantic.BaseModel):
filename: str
def _on_do_backup(self, event: ops.ActionEvent):
params = event.load_params(BackupParams)
# params.filename contains the value passed by the Juju user.
Any additional positional or keyword arguments will be passed through to
the action class ``__init__``.
Args:
cls: A class that will accept the Juju parameters as keyword
arguments, and raise ``ValueError`` if validation fails.
errors: what to do if the parameters are invalid. If ``fail``, this
will set the action to failed with an appropriate message and
then immediately exit. If ``raise``, ``load_params`` will not
catch any exceptions, leaving the charm to handle errors.
args: positional arguments to pass through to the action class.
kwargs: keyword arguments to pass through to the action class.
Returns:
An instance of the action class that was provided in the ``cls``
argument with the provided parameter values.
Raises:
ValueError: if ``errors`` is set to ``raise`` and instantiating the
action class raises a ValueError.
"""
try:
fields = _juju_fields(cls)
except ValueError:
fields = None
params: dict[str, Any] = kwargs.copy()
for key, value in sorted(self.params.items()):
attr = key.replace('-', '_')
if fields is None:
params[attr] = value
else:
if attr not in fields:
continue
params[fields[attr]] = value
try:
return cls(*args, **params)
except ValueError as e:
if errors == 'raise':
raise
self.fail(f'Error in action parameters: {e}')
from ._main import _Abort
raise _Abort(0) from e
def __repr__(self):
return f'<{self.__class__.__name__} {self.id=} via {self.handle}>'
[docs]
class InstallEvent(HookEvent):
"""Event triggered when a charm is installed.
This event is triggered at the beginning of a charm's
lifecycle. Any associated callback method should be used to
perform one-time setup operations, such as installing prerequisite
software.
"""
[docs]
class StartEvent(HookEvent):
"""Event triggered immediately after first configuration change.
This event is triggered immediately after the first
:class:`~ops.ConfigChangedEvent`. Callback methods bound to the event should be
used to ensure that the charm's software is in a running state. Note that
the charm's software should be configured so as to persist in this state
through reboots without further intervention on Juju's part.
"""
[docs]
class StopEvent(HookEvent):
"""Event triggered when a charm is shut down.
This event is triggered when an application's removal is requested
by the client. The event fires immediately before the end of the
unit's destruction sequence. Callback methods bound to this event
should be used to ensure that the charm's software is not running,
and that it will not start again on reboot.
"""
[docs]
def defer(self) -> NoReturn:
"""Stop events are not deferrable like other events.
This is because the unit is in the process of tearing down, and there
will not be an opportunity for the deferred event to run.
Raises:
RuntimeError: always.
"""
raise RuntimeError('cannot defer stop events')
[docs]
class RemoveEvent(HookEvent):
"""Event triggered when a unit is about to be terminated.
This event fires prior to Juju removing the charm and terminating its unit.
"""
[docs]
def defer(self) -> NoReturn:
"""Remove events are not deferrable like other events.
This is because the unit is about to be torn down, and there
will not be an opportunity for the deferred event to run.
Raises:
RuntimeError: always.
"""
raise RuntimeError('cannot defer remove events')
[docs]
class ConfigChangedEvent(HookEvent):
"""Event triggered when a configuration change occurs.
This event will fire in several situations:
- When the admin reconfigures the charm using the Juju CLI, for example
``juju config mycharm foo=bar``. This event notifies the charm of
its new configuration. (The event itself, however, is not aware of *what*
specifically has changed in the config).
- Right after the unit starts up for the first time.
This event notifies the charm of its initial configuration.
Typically, this event will fire between an :class:`~ops.InstallEvent`
and a :class:~`ops.StartEvent` during the startup sequence
(when a unit is first deployed), but in general it will fire whenever
the unit is (re)started, for example after pod churn on Kubernetes, on unit
rescheduling, on unit upgrade or refresh, and so on.
- As a specific instance of the above point: when networking changes
(if the machine reboots and comes up with a different IP).
- When the app config changes, for example when `juju trust` is run.
Any callback method bound to this event cannot assume that the
software has already been started; it should not start stopped
software, but should (if appropriate) restart running software to
take configuration changes into account.
"""
[docs]
class UpdateStatusEvent(HookEvent):
"""Event triggered by a status update request from Juju.
This event is periodically triggered by Juju so that it can
provide constant feedback to the administrator about the status of
the application the charm is modeling. Any callback method bound
to this event should determine the "health" of the application and
set the status appropriately.
The interval between :class:`~ops.UpdateStatusEvent` events can
be configured model-wide, e.g. ``juju model-config
update-status-hook-interval=1m``.
"""
[docs]
class UpgradeCharmEvent(HookEvent):
"""Event triggered by request to upgrade the charm.
This event will be triggered when an administrator executes ``juju
upgrade-charm``. The event fires after Juju has unpacked the upgraded charm
code, and so this event will be handled by the callback method bound to the
event in the new codebase. The associated callback method is invoked
provided there is no existing error state. The callback method should be
used to reconcile current state written by an older version of the charm
into whatever form that is needed by the current charm version.
"""
[docs]
class PreSeriesUpgradeEvent(HookEvent):
"""Event triggered to prepare a unit for series upgrade.
This event triggers when an administrator executes ``juju upgrade-machine
<machine> prepare``. The event will fire for each unit that is running on the
specified machine. Any callback method bound to this event must prepare the
charm for an upgrade to the series. This may include things like exporting
database content to a version neutral format, or evacuating running
instances to other machines.
It can be assumed that only after all units on a machine have executed the
callback method associated with this event, the administrator will initiate
steps to actually upgrade the series. After the upgrade has been completed,
the :class:`~ops.PostSeriesUpgradeEvent` will fire.
.. jujuremoved:: 4.0
"""
def __init__(self, handle: Handle):
warnings.warn(
'pre-series-upgrade events will not be emitted from Juju 4.0 onwards',
DeprecationWarning,
stacklevel=3,
)
super().__init__(handle)
[docs]
class PostSeriesUpgradeEvent(HookEvent):
"""Event triggered after a series upgrade.
This event is triggered after the administrator has done a distribution
upgrade (or rolled back and kept the same series). It is called in response
to ``juju upgrade-machine <machine> complete``. Associated charm callback
methods are expected to do whatever steps are necessary to reconfigure their
applications for the new series. This may include things like populating the
upgraded version of a database. Note however charms are expected to check if
the series has actually changed or whether it was rolled back to the
original series.
.. jujuremoved:: 4.0
"""
def __init__(self, handle: Handle):
warnings.warn(
'post-series-upgrade events will not be emitted from Juju 4.0 onwards',
DeprecationWarning,
stacklevel=3,
)
super().__init__(handle)
[docs]
class LeaderElectedEvent(HookEvent):
"""Event triggered when a new leader has been elected.
Juju will trigger this event when a new leader unit is chosen for
a given application.
This event fires at least once after Juju selects a leader
unit. Callback methods bound to this event may take any action
required for the elected unit to assert leadership. Note that only
the elected leader unit will receive this event.
"""
[docs]
class LeaderSettingsChangedEvent(HookEvent):
"""Event triggered when leader changes any settings.
.. deprecated:: 2.4.0
This event has been deprecated in favor of using a Peer relation,
and having the leader set a value in the Application data bag for
that peer relation. (See :class:`~ops.RelationChangedEvent`.)
"""
[docs]
class CollectMetricsEvent(HookEvent):
"""Event triggered by Juju to collect metrics.
Juju fires this event every five minutes for the lifetime of the
unit. Callback methods bound to this event may use the :meth:`add_metrics`
method of this class to send measurements to Juju.
Note that associated callback methods are currently sandboxed in
how they can interact with Juju.
.. jujuremoved:: 4.0
"""
def __init__(self, handle: Handle):
warnings.warn(
'collect-metrics events will not be emitted from Juju 4.0 onwards - '
'consider using the Canonical Observability Stack',
DeprecationWarning,
stacklevel=3,
)
super().__init__(handle)
[docs]
def add_metrics(
self, metrics: Mapping[str, int | float], labels: Mapping[str, str] | None = None
):
"""Record metrics that have been gathered by the charm for this unit.
Args:
metrics: Key-value mapping of metrics that have been gathered.
labels: Key-value labels applied to the metrics.
Raises:
ModelError: if invalid keys or values are provided.
"""
self.framework.model._backend.add_metrics(metrics, labels)
[docs]
class RelationEvent(HookEvent):
"""A base class representing the various relation lifecycle events.
Relation lifecycle events are generated when application units
participate in relations. Units can only participate in relations
after they have been "started", and before they have been
"stopped". Within that time window, the unit may participate in
several different relations at a time, including multiple
relations with the same name.
"""
relation: model.Relation
"""The relation involved in this event."""
app: model.Application
"""The remote application that has triggered this event."""
unit: model.Unit | None
"""The remote unit that has triggered this event.
This will be ``None`` if the relation event was triggered as an
:class:`Application <model.Application>`-level event.
"""
def __init__(
self,
handle: Handle,
relation: model.Relation,
app: model.Application | None = None,
unit: model.Unit | None = None,
):
super().__init__(handle)
if unit is not None and unit.app != app:
raise RuntimeError(
f'cannot create RelationEvent with application {app} and unit {unit}'
)
self.relation = relation
if app is None:
logger.warning(
"'app' expected but not received, see https://bugs.launchpad.net/juju/+bug/1960934"
)
# Do an explicit assignment here so that we can contain the type: ignore.
self.app = None # type: ignore
else:
self.app = app
self.unit = unit
[docs]
def snapshot(self) -> dict[str, Any]:
"""Used by the framework to serialize the event to disk.
Not meant to be called by charm code.
"""
snapshot: dict[str, Any] = {
'relation_name': self.relation.name,
'relation_id': self.relation.id,
}
if self.app:
snapshot['app_name'] = self.app.name
if self.unit:
snapshot['unit_name'] = self.unit.name
return snapshot
[docs]
def restore(self, snapshot: dict[str, Any]):
"""Used by the framework to deserialize the event from disk.
Not meant to be called by charm code.
"""
relation = self.framework.model.get_relation(
snapshot['relation_name'], snapshot['relation_id']
)
if relation is None:
raise ValueError(
'Unable to restore {}: relation {} (id={}) not found.'.format(
self, snapshot['relation_name'], snapshot['relation_id']
)
)
self.relation = relation
app_name = snapshot.get('app_name')
if app_name:
self.app = self.framework.model.get_app(app_name)
else:
logger.warning("'app_name' expected in snapshot but not found.")
self.app = None # type: ignore
unit_name = snapshot.get('unit_name')
if unit_name:
self.unit = self.framework.model.get_unit(unit_name)
else:
self.unit = None
def __repr__(self):
app = None if self.app is None else self.app.name
unit = None if self.unit is None else self.unit.name
return f'<{self.__class__.__name__} {app=} {unit=} on {self.relation!r} via {self.handle}>'
[docs]
class RelationCreatedEvent(RelationEvent):
"""Event triggered when a new relation is created.
This is triggered when a new relation with another app is added in Juju. This
can occur before units for those applications have started. All existing
relations will trigger `RelationCreatedEvent` before :class:`~ops.StartEvent` is
emitted.
"""
unit: None # pyright: ignore[reportIncompatibleVariableOverride]
"""Always ``None``."""
[docs]
class RelationJoinedEvent(RelationEvent):
"""Event triggered when a new unit joins a relation.
This event is triggered whenever a new unit of an integrated
application joins the relation. The event fires only when that
remote unit is first observed by the unit. Callback methods bound
to this event may set any local unit data that can be
determined using no more than the name of the joining unit and the
remote ``private-address`` setting, which is always available when
the relation is created and is by convention not deleted.
"""
unit: model.Unit # pyright: ignore[reportIncompatibleVariableOverride]
"""The remote unit that has triggered this event."""
[docs]
class RelationChangedEvent(RelationEvent):
"""Event triggered when relation data changes.
This event is triggered whenever there is a change to the data bucket for an
integrated application or unit. Look at ``event.relation.data[event.unit/app]``
to see the new information, where ``event`` is the event object passed to
the callback method bound to this event.
This event always fires once, after :class:`~ops.RelationJoinedEvent`, and
will subsequently fire whenever that remote unit changes its data for
the relation. Callback methods bound to this event should be the only ones
that rely on remote relation data. They should not error if the data
is incomplete, since it can be guaranteed that when the remote unit or
application changes its data, the event will fire again.
The data that may be queried, or set, are determined by the relation's
interface.
"""
[docs]
class RelationDepartedEvent(RelationEvent):
"""Event triggered when a unit leaves a relation.
This is the inverse of the :class:`~ops.RelationJoinedEvent`, representing when a
unit is leaving the relation (the unit is being removed, the app is being
removed, the relation is being removed). For remaining units, this event is
emitted once for each departing unit. For departing units, this event is
emitted once for each remaining unit.
Callback methods bound to this event may be used to remove all
references to the departing remote unit, because there's no
guarantee that it's still part of the system; it's perfectly
probable (although not guaranteed) that the system running that
unit has already shut down.
Once all callback methods bound to this event have been run for such a
relation, the unit agent will fire the :class:`~ops.RelationBrokenEvent`.
"""
unit: model.Unit # pyright: ignore[reportIncompatibleVariableOverride]
"""The remote unit that has triggered this event."""
def __init__(
self,
handle: Handle,
relation: model.Relation,
app: model.Application | None = None,
unit: model.Unit | None = None,
departing_unit_name: str | None = None,
):
super().__init__(handle, relation, app=app, unit=unit)
self._departing_unit_name = departing_unit_name
[docs]
def snapshot(self) -> dict[str, Any]:
"""Used by the framework to serialize the event to disk.
Not meant to be called by charm code.
"""
snapshot = super().snapshot()
if self._departing_unit_name:
snapshot['departing_unit'] = self._departing_unit_name
return snapshot
@property
def departing_unit(self) -> model.Unit | None:
"""The :class:`ops.Unit` that is departing, if any.
Use this method to determine (for example) whether this unit is the
departing one.
"""
# doing this on init would fail because `framework` gets patched in
# post-init
if not self._departing_unit_name:
return None
return self.framework.model.get_unit(self._departing_unit_name)
[docs]
def restore(self, snapshot: dict[str, Any]):
"""Used by the framework to deserialize the event from disk.
Not meant to be called by charm code.
"""
super().restore(snapshot)
self._departing_unit_name = snapshot.get('departing_unit')
[docs]
class RelationBrokenEvent(RelationEvent):
"""Event triggered when a relation is removed.
If a relation is being removed (``juju remove-relation`` or ``juju
remove-application``), once all the units have been removed, this event will
fire to signal that the relationship has been fully terminated.
The event indicates that the current relation is no longer valid, and that
the charm's software must be configured as though the relation had never
existed. It will only be called after every callback method bound to
:class:`~ops.RelationDepartedEvent` has been run. If a callback method
bound to this event is being executed, it is guaranteed that no remote units
are currently known locally.
"""
unit: None # pyright: ignore[reportIncompatibleVariableOverride]
"""Always ``None``."""
[docs]
class StorageEvent(HookEvent):
"""Base class representing events to do with storage.
Juju can provide a variety of storage types to a charms. The
charms can define several different types of storage that are
allocated from Juju. Changes in state of storage trigger sub-types
of :class:`StorageEvent`.
"""
storage: model.Storage
"""Storage instance this event refers to."""
def __init__(self, handle: Handle, storage: model.Storage):
super().__init__(handle)
self.storage = storage
[docs]
def snapshot(self) -> dict[str, Any]:
"""Used by the framework to serialize the event to disk.
Not meant to be called by charm code.
"""
snapshot: dict[str, Any] = {}
if isinstance(self.storage, model.Storage):
snapshot['storage_name'] = self.storage.name
snapshot['storage_index'] = self.storage.index
snapshot['storage_location'] = str(self.storage.location)
return snapshot
[docs]
def restore(self, snapshot: dict[str, Any]):
"""Used by the framework to deserialize the event from disk.
Not meant to be called by charm code.
"""
storage_name = snapshot.get('storage_name')
storage_index = snapshot.get('storage_index')
storage_location = snapshot.get('storage_location')
if storage_name and storage_index is not None:
storages = self.framework.model.storages[storage_name]
self.storage = next((s for s in storages if s.index == storage_index), None) # type: ignore
if self.storage is None:
raise RuntimeError(
f'failed loading storage (name={storage_name!r}, '
f'index={storage_index!r}) from snapshot'
)
if storage_location is None:
raise RuntimeError(
'failed loading storage location from snapshot.'
f'(name={storage_name!r}, index={storage_index!r}, storage_location=None)'
)
self.storage.location = storage_location
def __repr__(self):
return f'<{self.__class__.__name__} on {self.storage!r} via {self.handle}>'
[docs]
class StorageAttachedEvent(StorageEvent):
"""Event triggered when new storage becomes available.
This event is triggered when new storage is available for the
charm to use.
Callback methods bound to this event allow the charm to run code
when storage has been added. Such methods will be run before the
:class:`~ops.InstallEvent` fires, so that the installation routine may
use the storage. The name prefix of this hook will depend on the
storage key defined in the ``metadata.yaml`` file.
"""
[docs]
class StorageDetachingEvent(StorageEvent):
"""Event triggered prior to removal of storage.
This event is triggered when storage a charm has been using is
going away.
Callback methods bound to this event allow the charm to run code
before storage is removed. Such methods will be run before storage
is detached, and always before the :class:`~ops.StopEvent` fires, thereby
allowing the charm to gracefully release resources before they are
removed and before the unit terminates. The name prefix of the
hook will depend on the storage key defined in the ``metadata.yaml``
file.
"""
[docs]
class WorkloadEvent(HookEvent):
"""Base class representing events to do with the workload.
Workload events are generated for all containers that the charm
expects in metadata.
"""
workload: model.Container
"""The workload involved in this event.
Workload currently only can be a :class:`Container <model.Container>`, but
in future may be other types that represent the specific workload type,
for example a machine.
"""
def __init__(self, handle: Handle, workload: model.Container):
super().__init__(handle)
self.workload = workload
[docs]
def snapshot(self) -> dict[str, Any]:
"""Used by the framework to serialize the event to disk.
Not meant to be called by charm code.
"""
snapshot: dict[str, Any] = {}
if isinstance(self.workload, model.Container):
snapshot['container_name'] = self.workload.name
return snapshot
[docs]
def restore(self, snapshot: dict[str, Any]):
"""Used by the framework to deserialize the event from disk.
Not meant to be called by charm code.
"""
container_name = snapshot.get('container_name')
if container_name:
self.workload = self.framework.model.unit.get_container(container_name)
else:
self.workload = None # type: ignore
def __repr__(self):
return f'<{self.__class__.__name__} on {self.workload!r} via {self.handle}>'
[docs]
class PebbleReadyEvent(WorkloadEvent):
"""Event triggered when Pebble is ready for a workload.
This event is triggered when the Pebble process for a workload/container
starts up, allowing the charm to configure how services should be launched.
Callback methods bound to this event allow the charm to run code after
a workload has started its Pebble instance and is ready to receive instructions
regarding what services should be started. The name prefix of the hook
will depend on the container key defined in the ``metadata.yaml`` file.
"""
[docs]
class PebbleNoticeEvent(WorkloadEvent):
"""Base class for Pebble notice events (each notice type is a subclass)."""
notice: model.LazyNotice
"""Provide access to the event notice's details."""
def __init__(
self,
handle: Handle,
workload: model.Container,
notice_id: str,
notice_type: str,
notice_key: str,
):
super().__init__(handle, workload)
self.notice = model.LazyNotice(workload, notice_id, notice_type, notice_key)
[docs]
def snapshot(self) -> dict[str, Any]:
"""Used by the framework to serialize the event to disk.
Not meant to be called by charm code.
"""
d = super().snapshot()
d['notice_id'] = self.notice.id
d['notice_type'] = (
self.notice.type if isinstance(self.notice.type, str) else self.notice.type.value
)
d['notice_key'] = self.notice.key
return d
[docs]
def restore(self, snapshot: dict[str, Any]):
"""Used by the framework to deserialize the event from disk.
Not meant to be called by charm code.
"""
super().restore(snapshot)
notice_id = snapshot.pop('notice_id')
notice_type = snapshot.pop('notice_type')
notice_key = snapshot.pop('notice_key')
self.notice = model.LazyNotice(self.workload, notice_id, notice_type, notice_key)
[docs]
class PebbleCustomNoticeEvent(PebbleNoticeEvent):
"""Event triggered when a Pebble notice of type "custom" is created or repeats.
.. jujuadded:: 3.4
"""
[docs]
class PebbleCheckEvent(WorkloadEvent):
"""Base class for Pebble check events."""
info: model.LazyCheckInfo
"""Provide access to the check's current state."""
def __init__(
self,
handle: Handle,
workload: model.Container,
check_name: str,
):
super().__init__(handle, workload)
self.info = model.LazyCheckInfo(workload, check_name)
[docs]
def snapshot(self) -> dict[str, Any]:
"""Used by the framework to serialize the event to disk.
Not meant to be called by charm code.
"""
d = super().snapshot()
d['check_name'] = self.info.name
return d
[docs]
def restore(self, snapshot: dict[str, Any]):
"""Used by the framework to deserialize the event from disk.
Not meant to be called by charm code.
"""
check_name = snapshot.pop('check_name')
super().restore(snapshot)
self.info = model.LazyCheckInfo(self.workload, check_name)
[docs]
class PebbleCheckFailedEvent(PebbleCheckEvent):
"""Event triggered when a Pebble check exceeds the configured failure threshold.
Note that the check may have started passing by the time this event is
emitted (which will mean that a :class:`~ops.PebbleCheckRecoveredEvent` will be
emitted next). If the handler is executing code that should only be done
if the check is currently failing, check the current status with
``event.info.status == ops.pebble.CheckStatus.DOWN``.
.. jujuadded:: 3.6
"""
[docs]
class PebbleCheckRecoveredEvent(PebbleCheckEvent):
"""Event triggered when a Pebble check recovers.
This event is only triggered when the check has previously reached a failure
state (not simply failed, but failed at least as many times as the
configured threshold).
.. jujuadded:: 3.6
"""
[docs]
class SecretEvent(HookEvent):
"""Base class for all secret events."""
def __init__(self, handle: Handle, id: str, label: str | None):
super().__init__(handle)
self._id = id
self._label = label
@property
def secret(self) -> model.Secret:
"""The secret instance this event refers to.
Note that the secret content is not retrieved from the secret storage
until :meth:`Secret.get_content()` is called.
"""
backend = self.framework.model._backend
return model.Secret(
backend=backend,
id=self._id,
label=self._label,
_secret_set_cache=self.framework.model._cache._secret_set_cache,
)
[docs]
def snapshot(self) -> dict[str, Any]:
"""Used by the framework to serialize the event to disk.
Not meant to be called by charm code.
"""
return {'id': self._id, 'label': self._label}
[docs]
def restore(self, snapshot: dict[str, Any]):
"""Used by the framework to deserialize the event from disk.
Not meant to be called by charm code.
"""
self._id = cast('str', snapshot['id'])
self._label = cast('Optional[str]', snapshot['label'])
[docs]
class SecretChangedEvent(SecretEvent):
"""Event triggered on the secret observer charm when the secret owner changes its contents.
When the owner of a secret changes the secret's contents, Juju will create
a new secret revision, and all applications or units that are tracking this
secret will be notified via this event that a new revision is available.
Typically, the charm will fetch the new content by calling
:meth:`event.secret.get_content() <ops.Secret.get_content>` with ``refresh=True``
to tell Juju to start tracking the new revision.
.. jujuadded:: 3.0
Charm secrets added in Juju 3.0, user secrets added in Juju 3.3
"""
[docs]
class SecretRotateEvent(SecretEvent):
"""Event triggered on the secret owner charm when the secret's rotation policy elapses.
This event is fired on the secret owner to inform it that the secret must
be rotated. The event will keep firing until the owner creates a new
revision by calling :meth:`event.secret.set_content() <ops.Secret.set_content>`.
.. jujuadded:: 3.0
"""
[docs]
def defer(self) -> NoReturn:
"""Secret rotation events are not deferrable (Juju handles re-invocation).
Raises:
RuntimeError: always.
"""
raise RuntimeError(
'Cannot defer secret rotation events. Juju will keep firing this '
'event until you create a new revision.'
)
[docs]
class SecretRemoveEvent(SecretEvent):
"""Event triggered on the secret owner charm when a secret revision can be removed.
When the owner of a secret creates a new revision, and after all
observers have updated to that new revision, this event will be fired to
inform the secret owner that the old revision can be removed.
After any required cleanup, the charm should call
:meth:`event.remove_revision() <ops.SecretRemoveEvent.remove_revision>` to
remove the now-unused revision. If the charm does not, then the event will
be emitted again, when further revisions are ready for removal.
.. jujuadded:: 3.0
"""
def __init__(self, handle: Handle, id: str, label: str | None, revision: int):
super().__init__(handle, id, label)
self._revision = revision
@property
def revision(self) -> int:
"""The secret revision this event refers to."""
return self._revision
[docs]
def remove_revision(self):
"""Remove the revision this event refers to.
Call this method after any required cleanup to inform Juju that the
secret revision can be removed.
"""
self.secret.remove_revision(self._revision)
[docs]
def snapshot(self) -> dict[str, Any]:
"""Used by the framework to serialize the event to disk.
Not meant to be called by charm code.
"""
data = super().snapshot()
data['revision'] = self._revision
return data
[docs]
def restore(self, snapshot: dict[str, Any]):
"""Used by the framework to deserialize the event from disk.
Not meant to be called by charm code.
"""
super().restore(snapshot)
self._revision = cast('int', snapshot['revision'])
[docs]
class SecretExpiredEvent(SecretEvent):
"""Event triggered on the secret owner charm when a secret's expiration time elapses.
This event is fired on the secret owner to inform it that the secret revision
must be removed. The event will keep firing until the owner removes the
revision by calling :meth:`event.remove_revision()
<ops.SecretExpiredEvent.remove_revision>`.
.. jujuadded:: 3.0
"""
def __init__(self, handle: Handle, id: str, label: str | None, revision: int):
super().__init__(handle, id, label)
self._revision = revision
@property
def revision(self) -> int:
"""The secret revision this event refers to."""
return self._revision
[docs]
def remove_revision(self):
"""Remove the revision this event refers to.
Call this method after any required cleanup to inform Juju that the
secret revision can be removed.
"""
self.secret.remove_revision(self._revision)
[docs]
def snapshot(self) -> dict[str, Any]:
"""Used by the framework to serialize the event to disk.
Not meant to be called by charm code.
"""
data = super().snapshot()
data['revision'] = self._revision
return data
[docs]
def restore(self, snapshot: dict[str, Any]):
"""Used by the framework to deserialize the event from disk.
Not meant to be called by charm code.
"""
super().restore(snapshot)
self._revision = cast('int', snapshot['revision'])
[docs]
def defer(self) -> NoReturn:
"""Secret expiration events are not deferrable (Juju handles re-invocation).
Raises:
RuntimeError: always.
"""
raise RuntimeError(
'Cannot defer secret expiration events. Juju will keep firing '
'this event until you create a new revision.'
)
[docs]
class CollectStatusEvent(LifecycleEvent):
"""Event triggered at the end of every hook to collect statuses for evaluation.
If the charm wants to provide application or unit status in a consistent
way after the end of every hook, it should observe the
:attr:`collect_app_status <CharmEvents.collect_app_status>` or
:attr:`collect_unit_status <CharmEvents.collect_unit_status>` event,
respectively.
The framework will trigger these events after the hook code runs
successfully (``collect_app_status`` will only be triggered on the leader
unit). This happens on every Juju event, whether it was
:meth:`observed <ops.Framework.observe>` or not.
If any statuses were added by the event handler using
:meth:`add_status`, the framework will choose the highest-priority status
and set that as the status (application status for ``collect_app_status``,
or unit status for ``collect_unit_status``).
The order of priorities is as follows, from highest to lowest:
* blocked
* maintenance
* waiting
* active
It is an error to call :meth:`add_status` with an instance of
:class:`ErrorStatus` or :class:`UnknownStatus`.
If there are multiple statuses with the same priority, the first one added
wins (and if an event is observed multiple times, the handlers are called
in the order they were observed).
A collect-status event can be observed multiple times, and
:meth:`add_status` can be called multiple times to add multiple statuses
for evaluation. This is useful when a charm has multiple components that
each have a status. Each code path in a collect-status handler should
call ``add_status`` at least once.
Below is an example "web app" charm component that observes
``collect_unit_status`` to provide the status of the component, which
requires a "port" config option set before it can proceed::
class MyCharm(ops.CharmBase):
def __init__(self, framework: ops.Framework):
super().__init__(framework)
self.webapp = Webapp(self)
# initialize other components
class WebApp(ops.Object):
def __init__(self, charm: ops.CharmBase):
super().__init__(charm, 'webapp')
self.framework.observe(charm.on.collect_unit_status, self._on_collect_status)
def _on_collect_status(self, event: ops.CollectStatusEvent):
if 'port' not in self.model.config:
event.add_status(ops.BlockedStatus('please set "port" config'))
return
event.add_status(ops.ActiveStatus())
""" # noqa: D405, D214, D411, D416 Final return confuses docstyle.
[docs]
def add_status(self, status: model.StatusBase):
"""Add a status for evaluation.
See :class:`CollectStatusEvent` for a description of how to use this.
"""
if not isinstance(status, model.StatusBase):
raise TypeError(f'status should be a StatusBase, not {type(status).__name__}')
if status.name not in model._SETTABLE_STATUS_NAMES:
raise model.InvalidStatusError(
f'status.name must be in {model._SETTABLE_STATUS_NAMES}, not {status.name!r}'
)
model_ = self.framework.model
if self.handle.kind == 'collect_app_status':
if not isinstance(status, model.ActiveStatus):
logger.debug('Adding app status %s', status, stacklevel=2)
model_.app._collected_statuses.append(status)
else:
if not isinstance(status, model.ActiveStatus):
logger.debug('Adding unit status %s', status, stacklevel=2)
model_.unit._collected_statuses.append(status)
[docs]
class CharmEvents(ObjectEvents):
"""Events generated by Juju pertaining to application lifecycle.
By default, the events listed as attributes of this class will be
provided via the :attr:`CharmBase.on` attribute. For example::
framework.observe(self.on.config_changed, self._on_config_changed)
In addition to the events listed as attributes of this class,
dynamically-named events will also be defined based on the charm's
metadata (``metadata.yaml``) for relations, storage, actions, and
containers. These named events may be accessed as
``self.on[<name>].<event>`` or using a prefix like
``self.on.<name>_<event>``, for example::
framework.observe(self.on["db"].relation_created, self._on_db_relation_created)
framework.observe(self.on.workload_pebble_ready, self._on_workload_pebble_ready)
"""
# NOTE: The one-line docstrings below are copied from the first line of
# each event class's docstring. Please keep in sync.
install = EventSource(InstallEvent)
"""Triggered when a charm is installed (see :class:`~ops.InstallEvent`)."""
start = EventSource(StartEvent)
"""Triggered immediately after first configuration change (see :class:`~ops.StartEvent`)."""
stop = EventSource(StopEvent)
"""Triggered when a charm is shut down (see :class:`~ops.StopEvent`)."""
remove = EventSource(RemoveEvent)
"""Triggered when a unit is about to be terminated (see :class:`~ops.RemoveEvent`)."""
update_status = EventSource(UpdateStatusEvent)
"""Triggered periodically by a status update request from Juju (see
:class:`~ops.UpdateStatusEvent`).
"""
config_changed = EventSource(ConfigChangedEvent)
"""Triggered when a configuration change occurs (see :class:`~ops.ConfigChangedEvent`)."""
upgrade_charm = EventSource(UpgradeCharmEvent)
"""Triggered by request to upgrade the charm (see :class:`~ops.UpgradeCharmEvent`)."""
pre_series_upgrade = EventSource(PreSeriesUpgradeEvent)
"""Triggered to prepare a unit for series upgrade (see :class:`~ops.PreSeriesUpgradeEvent`).
.. jujuremoved:: 4.0
"""
post_series_upgrade = EventSource(PostSeriesUpgradeEvent)
"""Triggered after a series upgrade (see :class:`~ops.PostSeriesUpgradeEvent`).
.. jujuremoved:: 4.0
"""
leader_elected = EventSource(LeaderElectedEvent)
"""Triggered when a new leader has been elected (see :class:`~ops.LeaderElectedEvent`)."""
leader_settings_changed = EventSource(LeaderSettingsChangedEvent)
"""Triggered when leader changes any settings (see
:class:`~ops.LeaderSettingsChangedEvent`).
.. deprecated:: 2.4.0
"""
collect_metrics = EventSource(CollectMetricsEvent)
"""Triggered by Juju to collect metrics (see :class:`~ops.CollectMetricsEvent`).
.. jujuremoved:: 4.0
"""
secret_changed = EventSource(SecretChangedEvent)
"""Triggered by Juju on the observer when the secret owner changes its contents (see
:class:`~ops.SecretChangedEvent`).
.. jujuadded:: 3.0
Charm secrets added in Juju 3.0, user secrets added in Juju 3.3
"""
secret_expired = EventSource(SecretExpiredEvent)
"""Triggered by Juju on the owner when a secret's expiration time elapses (see
:class:`~ops.SecretExpiredEvent`).
.. jujuadded:: 3.0
"""
secret_rotate = EventSource(SecretRotateEvent)
"""Triggered by Juju on the owner when the secret's rotation policy elapses (see
:class:`~ops.SecretRotateEvent`).
.. jujuadded:: 3.0
"""
secret_remove = EventSource(SecretRemoveEvent)
"""Triggered by Juju on the owner when a secret revision can be removed (see
:class:`~ops.SecretRemoveEvent`).
.. jujuadded:: 3.0
"""
collect_app_status = EventSource(CollectStatusEvent)
"""Triggered on the leader at the end of every hook to collect app statuses for evaluation
(see :class:`~ops.CollectStatusEvent`).
"""
collect_unit_status = EventSource(CollectStatusEvent)
"""Triggered at the end of every hook to collect unit statuses for evaluation
(see :class:`~ops.CollectStatusEvent`).
"""
_T = TypeVar('_T')
[docs]
class CharmBase(Object):
"""Base class that represents the charm overall.
:code:`CharmBase` is used to create a charm. This is done by inheriting
from :code:`CharmBase` and customising the subclass as required. So to
create a charm called ``MyCharm``, define a charm class and set up the
required event handlers (“hooks”) in its constructor::
import logging
import ops
class MyCharm(ops.CharmBase):
def __init__(self, framework: ops.Framework):
super().__init__(framework)
framework.observe(self.on.config_changed, self._on_config_changed)
framework.observe(self.on.stop, self._on_stop)
# ...
if __name__ == "__main__":
ops.main(MyCharm)
As shown in the example above, a charm class is instantiated by
:code:`ops.main` rather than charm authors directly instantiating a
charm.
Args:
framework: The framework responsible for managing the Model and events for this
charm.
"""
on: CharmEvents = CharmEvents() # type: ignore
"""This property is used to create an event handler using :meth:`Framework.observe`,
and can be one of the events listed at :class:`CharmEvents`.
"""
if TYPE_CHECKING:
# to help the type checker and IDEs:
[docs]
@property
def on(self) -> CharmEvents: ... # noqa
def __init__(self, framework: Framework):
super().__init__(framework, None)
for relation_name in self.framework.meta.relations:
relation_name = relation_name.replace('-', '_')
self.on.define_event(f'{relation_name}_relation_created', RelationCreatedEvent)
self.on.define_event(f'{relation_name}_relation_joined', RelationJoinedEvent)
self.on.define_event(f'{relation_name}_relation_changed', RelationChangedEvent)
self.on.define_event(f'{relation_name}_relation_departed', RelationDepartedEvent)
self.on.define_event(f'{relation_name}_relation_broken', RelationBrokenEvent)
for storage_name in self.framework.meta.storages:
storage_name = storage_name.replace('-', '_')
self.on.define_event(f'{storage_name}_storage_attached', StorageAttachedEvent)
self.on.define_event(f'{storage_name}_storage_detaching', StorageDetachingEvent)
for action_name in self.framework.meta.actions:
action_name = action_name.replace('-', '_')
self.on.define_event(f'{action_name}_action', ActionEvent)
for container_name in self.framework.meta.containers:
container_name = container_name.replace('-', '_')
self.on.define_event(f'{container_name}_pebble_ready', PebbleReadyEvent)
self.on.define_event(f'{container_name}_pebble_custom_notice', PebbleCustomNoticeEvent)
self.on.define_event(f'{container_name}_pebble_check_failed', PebbleCheckFailedEvent)
self.on.define_event(
f'{container_name}_pebble_check_recovered', PebbleCheckRecoveredEvent
)
@property
def app(self) -> model.Application:
"""Application that this unit is part of."""
return self.framework.model.app
@property
def unit(self) -> model.Unit:
"""Unit that this execution is responsible for."""
return self.framework.model.unit
@property
def meta(self) -> CharmMeta:
"""Metadata of this charm."""
return self.framework.meta
@property
def charm_dir(self) -> pathlib.Path:
"""Root directory of the charm as it is running."""
return self.framework.charm_dir
@property
def config(self) -> model.ConfigData:
"""A mapping containing the charm's config and current values."""
return self.model.config
[docs]
def load_config(
self,
cls: type[_T],
*args: Any,
errors: Literal['raise', 'blocked'] = 'raise',
**kwargs: Any,
) -> _T:
"""Load the config into an instance of a config class.
The raw Juju config is passed to the config class's ``__init__``, as
keyword arguments, with the following changes:
* ``secret`` type options have a :class:`model.Secret` value rather
than the secret ID. Note that the secret object is not validated by
Juju at this time, so may raise :class:`SecretNotFoundError` when it
is used later (if the secret does not exist or the unit does not have
permission to access it).
* dashes in names are converted to underscores.
For dataclasses and Pydantic ``BaseModel`` subclasses, only fields in
the Juju config that have a matching field in the class are passed as
arguments. Pydantic fields that have an ``alias``, or dataclasses that
have a ``metadata{'alias'=}``, will have the alias applied when loading.
For example::
class Config(pydantic.BaseModel):
# This field is called 'class' in the Juju config options.
workload_class: str = pydantic.Field(alias='class')
def _on_config_changed(self, event: ops.ConfigChangedEvent):
data = self.load_config(Config, errors='blocked')
# `data.workload_class` has the value of the Juju option `class`
Any additional positional or keyword arguments to this method will be
passed through to the config class ``__init__``.
Args:
cls: A class that will accept the Juju options as keyword arguments,
and raise ``ValueError`` if validation fails.
errors: what to do if the config is invalid. If ``blocked``, this
will set the unit status to blocked with an appropriate message
and then exit successfully (this informs Juju that
the event was handled and it will not be retried).
If ``raise``, ``load_config``
will not catch any exceptions, leaving the charm to handle
errors.
args: positional arguments to pass through to the config class.
kwargs: keyword arguments to pass through to the config class.
Returns:
An instance of the config class that was passed in the ``cls`` argument
with the current config values.
Raises:
ValueError: if the configuration is invalid and ``errors`` is set to
``raise``.
"""
from ._main import _Abort
config: dict[str, bool | int | float | str | model.Secret] = kwargs.copy()
try:
fields = set(_juju_fields(cls))
except ValueError:
fields = None
for key, value in self.config.items():
attr = key.replace('-', '_')
if fields is not None and attr not in fields:
continue
option_type = self.meta.config.get(key)
# Convert secret IDs to secret objects. We create the object rather
# that using model.get_secret so that it's entirely lazy, in the
# same way that SecretEvent.secret is.
if option_type and option_type.type == 'secret':
assert isinstance(value, str) # Juju will have made sure of this.
value = model.Secret(
backend=self.model._backend,
id=value,
_secret_set_cache=self.model._cache._secret_set_cache,
)
config[attr] = value
try:
return cls(*args, **config)
except ValueError as e:
if errors == 'raise':
raise
# We exit with a zero code because we don't want Juju to retry
# (the config needs to be fixed by the Juju user), and we don't
# want the status we just set to be overridden by an error
# status.
self.unit.status = model.BlockedStatus(f'Invalid config: {e}')
raise _Abort(0) from e
def _evaluate_status(charm: CharmBase): # pyright: ignore[reportUnusedFunction]
"""Trigger collect-status events and evaluate and set the highest-priority status.
See :class:`CollectStatusEvent` for details.
"""
if charm.framework.model._backend.is_leader():
charm.on.collect_app_status.emit()
app = charm.app
if app._collected_statuses:
app.status = model.StatusBase._get_highest_priority(app._collected_statuses)
charm.on.collect_unit_status.emit()
unit = charm.unit
if unit._collected_statuses:
unit.status = model.StatusBase._get_highest_priority(unit._collected_statuses)
def _juju_fields(cls: type[object]) -> dict[str, str]:
"""Iterates over all the field names to include when loading into a class.
Any Juju names that are not in the returned dictionary should not be passed
to the class. Names that are in the dictionary are mapped to the argument
name; in most cases this is the same string, but for aliases will differ.
Returns:
A dictionary where the key is the Juju name and the value is the name of
the attribute in the Python class.
Raises:
ValueError: if unable to determine which fields to include
"""
# Dataclasses:
juju_to_arg: dict[str, str] = {}
if dataclasses.is_dataclass(cls):
for field in dataclasses.fields(cls):
alias = field.metadata.get('alias', field.name)
# If this a Pydantic dataclass, then it handles the alias.
# Using pydantic.dataclasses.is_pydantic_dataclass() would be
# best here, but we don't want to import pydantic in ops, so
# we look more explicitly.
if getattr(cls, '__is_pydantic_dataclass__', False):
juju_to_arg[alias] = alias
else:
juju_to_arg[alias] = field.name
return juju_to_arg
# Pydantic models:
class_fields: dict[str, str] = {}
if hasattr(cls, 'model_fields'):
for name, field in cls.model_fields.items(): # type: ignore
# Pydantic takes care of the alias.
class_fields[field.alias or name] = field.alias or name # type: ignore
return class_fields
# It's not clear, so give up.
raise ValueError('Unable to find class fields')
[docs]
class RelationRole(enum.Enum):
"""An annotation for a charm's role in a relation.
For each relation a charm's role may be
- A Peer
- A service consumer in the relation ('requires')
- A service provider in the relation ('provides')
"""
peer = 'peer'
requires = 'requires'
provides = 'provides'
[docs]
def is_peer(self) -> bool:
"""Report whether this role is 'peer'.
``role.is_peer()`` is a shortcut for ``role == ops.RelationRole.peer``.
"""
return self is RelationRole.peer
[docs]
class JujuAssumesCondition(enum.Enum):
"""Distinguishes between :class:`JujuAssumes` that must match all or any features."""
ALL = 'all-of'
"""All features are required to satisfy the requirement."""
ANY = 'any-of'
"""Any of the features satisfies the requirement."""
[docs]
@dataclasses.dataclass(frozen=True)
class JujuAssumes:
"""Juju model features that are required by the charm.
See the `Charmcraft docs <https://canonical-charmcraft.readthedocs-hosted.com/en/stable/reference/files/charmcraft-yaml-file/#assumes>`_
for a list of available features.
"""
features: list[str | JujuAssumes]
condition: JujuAssumesCondition = JujuAssumesCondition.ALL
[docs]
@classmethod
def from_list(
cls,
raw: list[Any],
condition: JujuAssumesCondition = JujuAssumesCondition.ALL,
) -> JujuAssumes:
"""Create new JujuAssumes object from list parsed from YAML."""
features: list[str | JujuAssumes] = []
for feature in raw:
if isinstance(feature, str):
features.append(feature)
else:
for nested_condition, nested_features in feature.items():
features.append(
JujuAssumes.from_list(
nested_features, JujuAssumesCondition(nested_condition)
)
)
return cls(features=features, condition=condition)
[docs]
@dataclasses.dataclass(frozen=True)
class ContainerBase:
"""Metadata to resolve a container image."""
os_name: str
"""Name of the OS.
For example: ``ubuntu``
"""
channel: str
"""Channel of the OS in format ``track[/risk][/branch]`` as used by Snaps.
For example: ``20.04/stable`` or ``18.04/stable/fips``
"""
architectures: list[str]
"""List of architectures that this charm can run on."""
[docs]
@classmethod
def from_dict(cls, d: _ContainerBaseDict) -> ContainerBase:
"""Create new ContainerBase object from dict parsed from YAML."""
return cls(
os_name=d['name'],
channel=d['channel'],
architectures=d['architectures'],
)
