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# 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.
from __future__ import annotations
import logging
import os
import signal
import typing
if typing.TYPE_CHECKING:
from cotyledon import types
LOG = logging.getLogger(__name__)
class Service:
"""Base class for a service
This class will be executed in a new child process/worker
:py:class:`ServiceWorker` of a :py:class:`ServiceManager`. It registers
signals to manager the reloading and the ending of the process.
Methods :py:meth:`run`, :py:meth:`terminate` and :py:meth:`reload` are
optional.
"""
name: typing.ClassVar[str | None] = None
"""Service name used in the process title and the log messages in
additional of the worker_id."""
graceful_shutdown_timeout: typing.ClassVar[int | None] = None
"""Timeout after which a gracefully shutdown service will exit. zero means
endless wait. None means same as ServiceManager that launch the service"""
def __init_subclass__(cls, **kwargs: typing.Any) -> None: # noqa: ANN401
super().__init_subclass__(**kwargs)
if cls.name is None:
cls.name = cls.__name__
def __init__(self, worker_id: types.WorkerId) -> None:
"""Create a new Service
:param worker_id: the identifier of this service instance
:type worker_id: int
The identifier of the worker can be used for workload repartition
because it's consistent and always the same.
For example, if the number of workers for this service is 3,
one will got 0, the second got 1 and the last got 2.
if worker_id 1 died, the new spawned process will got 1 again.
"""
super().__init__()
self.worker_id = worker_id
def terminate(self) -> None:
"""Gracefully shutdown the service
This method will be executed when the Service has to shutdown cleanly.
If not implemented the process will just end with status 0.
To customize the exit code, the :py:class:`SystemExit` exception can be
used.
Any exceptions raised by this method will be logged and the worker will
exit with status 1.
"""
def reload(self) -> None: # noqa: PLR6301
"""Reloading of the service
This method will be executed when the Service receives a SIGHUP.
If not implemented the process will just end with status 0 and
:py:class:`ServiceRunner` will start a new fresh process for this
service with the same worker_id.
Any exceptions raised by this method will be logged and the worker will
exit with status 1.
"""
os.kill(os.getpid(), signal.SIGTERM)
def run(self) -> None:
"""Method representing the service activity
If not implemented the process will just wait to receive an ending
signal.
This method is ran into the thread and can block or return as needed
Any exceptions raised by this method will be logged and the worker will
exit with status 1.
"""
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