2023-02-24 09:52:34 +00:00
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# Copyright 2023 Canonical Ltd.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Helpers for controlling whether jobs should run.
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In general it is better for a command to be a noop if run when it is not
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needed but in some cases the commands are expensive or disruptive in which
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case these helpers can limit how frequently they are run.
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"""
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import logging
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import time
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2024-08-07 17:25:48 +02:00
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import typing
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2023-02-24 09:52:34 +00:00
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from functools import (
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wraps,
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)
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import ops.framework
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2024-08-07 17:25:48 +02:00
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if typing.TYPE_CHECKING:
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2023-02-25 14:53:10 +00:00
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import ops_sunbeam.charm
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2023-02-24 09:52:34 +00:00
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logger = logging.getLogger(__name__)
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def run_once_per_unit(label):
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"""Run once per instantiation of a unit.
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This is designed for commands which only need to be run once on each
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instantiation of a unit.
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Note: This decorator can only be used within a charm derived from
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ops_sunbeam.charm.OSBaseOperatorCharm.
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Example usage:
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class MyCharm(ops_sunbeam.charm.OSBaseOperatorCharm):
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...
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@run_once_per_unit('a2enmod')
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def enable_apache_module(self):
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check_call(['a2enmod', 'wsgi'])
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"""
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def wrap(f):
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@wraps(f)
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def wrapped_f(
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charm: "ops_sunbeam.charm.OSBaseOperatorCharm", *args, **kwargs
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):
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"""Run once decorator.
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:param charm: Instance of charm
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"""
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storage = LocalJobStorage(charm._state)
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if label in storage:
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logging.warning(
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f"Not running {label}, it has run previously for this unit"
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)
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else:
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logging.warning(
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f"Running {label}, it has not run on this unit before"
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)
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f(charm, *args, **kwargs)
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storage.add(label)
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return wrapped_f
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return wrap
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class LocalJobStorage:
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"""Class to store job info of jobs run on the local unit."""
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def __init__(self, storage: ops.framework.BoundStoredState):
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"""Setup job history storage."""
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self.storage = storage
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try:
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self.storage.run_once
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except AttributeError:
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self.storage.run_once = {}
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def get_labels(self):
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"""Return all job entries."""
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return self.storage.run_once
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def __contains__(self, key):
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"""Check if label is in list or run jobs."""
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return key in self.get_labels().keys()
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def add(self, key):
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"""Add the label of job that has run."""
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self.storage.run_once[key] = str(time.time())
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