5de514f1f8
Introduces a new threading backend for oslo.service that provides a complete alternative to the eventlet-based backend. This backend includes: • A ThreadGroup and Thread implementation using the Python threading module. • A reimplementation of all looping call utilities ( FixedIntervalLoopingCall, DynamicLoopingCall, etc.) using threading.Event and futurist.ThreadPoolExecutor. • A service management layer based on cotyledon, including Service,ServiceWrapper, Launcher, and ProcessLauncher. • A new ThreadingBackend class that exposes all components needed for integration into oslo.service. This change provides a robust and eventlet-free alternative backend while maintaining API compatibility. Change-Id: Ia7518401ccdcc28afbffd4ffe5c3b772f3617001
156 lines
4.6 KiB
Python
156 lines
4.6 KiB
Python
# Copyright (C) 2024 Red Hat, Inc.
|
|
#
|
|
# 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 enum
|
|
import importlib
|
|
import logging
|
|
from typing import Any
|
|
from typing import Callable
|
|
from typing import TYPE_CHECKING
|
|
|
|
from . import exceptions
|
|
|
|
if TYPE_CHECKING:
|
|
from .base import BaseBackend
|
|
|
|
LOG = logging.getLogger(__name__)
|
|
|
|
|
|
class BackendType(enum.Enum):
|
|
EVENTLET = "eventlet"
|
|
THREADING = "threading"
|
|
|
|
|
|
DEFAULT_BACKEND_TYPE = BackendType.EVENTLET
|
|
|
|
_cached_backend_type: BackendType | None = None
|
|
_cached_backend: BaseBackend | None = None
|
|
_cached_components: dict[str, Any] | None = None
|
|
|
|
# optional override hook
|
|
_backend_hook: Callable[[], BackendType] | None = None
|
|
|
|
|
|
def register_backend_default_hook(hook: Callable[[], BackendType]) -> None:
|
|
"""Register a hook that decides the default backend type.
|
|
|
|
This is used when no init_backend() call has been made, and
|
|
get_backend() is called. The hook will be invoked to determine
|
|
the backend type to use *only if* no backend has been selected yet.
|
|
|
|
Example:
|
|
|
|
def my_hook():
|
|
return BackendType.THREADING
|
|
|
|
register_backend_default_hook(my_hook)
|
|
|
|
:param hook: A callable that returns a BackendType
|
|
"""
|
|
global _backend_hook
|
|
_backend_hook = hook
|
|
|
|
|
|
def _reset_backend() -> None:
|
|
"""Used by test functions to reset the selected backend."""
|
|
|
|
global _cached_backend, _cached_components
|
|
global _cached_backend_type, _backend_hook
|
|
|
|
_cached_backend_type = _cached_backend = _cached_components = None
|
|
_backend_hook = None
|
|
|
|
|
|
def init_backend(type_: BackendType) -> None:
|
|
"""Establish which backend will be used when get_backend() is called."""
|
|
|
|
global _cached_backend, _cached_components, _cached_backend_type
|
|
|
|
if _cached_backend_type is not None:
|
|
if _cached_backend_type != type_:
|
|
raise exceptions.BackendAlreadySelected(
|
|
f"Backend already set to {_cached_backend_type.value!r},"
|
|
f" cannot reinitialize with {type_.value!r}"
|
|
)
|
|
|
|
return # already initialized with same value; no-op
|
|
|
|
backend_name = type_.value
|
|
LOG.info(f"Loading backend: {backend_name}")
|
|
|
|
try:
|
|
module_name = f"oslo_service.backend.{backend_name}"
|
|
module = importlib.import_module(module_name)
|
|
backend_class = getattr(module, f"{backend_name.capitalize()}Backend")
|
|
|
|
new_backend: BaseBackend
|
|
_cached_backend = new_backend = backend_class()
|
|
|
|
except ModuleNotFoundError:
|
|
LOG.error(f"Backend module {module_name} not found.")
|
|
raise ValueError(f"Unknown backend: {backend_name!r}")
|
|
except AttributeError:
|
|
LOG.error(f"Backend class not found in module {module_name}.")
|
|
raise ImportError(f"Backend class not found in module {module_name}")
|
|
|
|
_cached_backend_type = type_
|
|
_cached_components = new_backend.get_service_components()
|
|
LOG.info(f"Backend {type_.value!r} successfully loaded and cached.")
|
|
|
|
|
|
def get_backend() -> BaseBackend:
|
|
"""Load backend dynamically based on the default constant or hook."""
|
|
|
|
global _cached_backend
|
|
if _cached_backend is None:
|
|
type_ = DEFAULT_BACKEND_TYPE
|
|
|
|
if _backend_hook is not None:
|
|
try:
|
|
type_ = _backend_hook()
|
|
LOG.info(f"Backend hook selected: {type_.value}")
|
|
except Exception:
|
|
LOG.exception(
|
|
"Backend hook raised an exception."
|
|
" Falling back to default.")
|
|
|
|
init_backend(type_)
|
|
|
|
assert _cached_backend is not None # nosec B101 : this is for typing
|
|
|
|
return _cached_backend
|
|
|
|
|
|
def get_backend_type() -> BackendType | None:
|
|
"""Return the type of the current backend, or None if not set."""
|
|
return _cached_backend_type
|
|
|
|
|
|
def get_component(name: str) -> Any:
|
|
"""Retrieve a specific component from the backend."""
|
|
global _cached_components
|
|
|
|
if _cached_components is None:
|
|
get_backend()
|
|
|
|
assert _cached_components is not None # nosec B101 : this is for typing
|
|
|
|
if name not in _cached_components:
|
|
raise KeyError(f"Component {name!r} not found in backend.")
|
|
|
|
return _cached_components[name]
|