151 lines
4.4 KiB
Python
151 lines
4.4 KiB
Python
# Copyright 2011 Yesudeep Mangalapilly <yesudeep@gmail.com>
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# Copyright 2012 Google, Inc & contributors.
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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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"""
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:module: libs.watchdog.utils
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:synopsis: Utility classes and functions.
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:author: yesudeep@google.com (Yesudeep Mangalapilly)
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:author: contact@tiger-222.fr (Mickaël Schoentgen)
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Classes
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-------
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.. autoclass:: BaseThread
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:members:
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:show-inheritance:
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:inherited-members:
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"""
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from __future__ import annotations
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import sys
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import threading
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from typing import TYPE_CHECKING
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class UnsupportedLibc(Exception):
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pass
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class WatchdogShutdown(Exception):
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"""
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Semantic exception used to signal an external shutdown event.
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"""
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pass
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class BaseThread(threading.Thread):
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"""Convenience class for creating stoppable threads."""
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def __init__(self):
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threading.Thread.__init__(self)
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if hasattr(self, "daemon"):
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self.daemon = True
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else:
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self.setDaemon(True)
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self._stopped_event = threading.Event()
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@property
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def stopped_event(self):
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return self._stopped_event
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def should_keep_running(self):
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"""Determines whether the thread should continue running."""
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return not self._stopped_event.is_set()
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def on_thread_stop(self):
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"""Override this method instead of :meth:`stop()`.
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:meth:`stop()` calls this method.
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This method is called immediately after the thread is signaled to stop.
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"""
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pass
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def stop(self):
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"""Signals the thread to stop."""
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self._stopped_event.set()
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self.on_thread_stop()
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def on_thread_start(self):
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"""Override this method instead of :meth:`start()`. :meth:`start()`
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calls this method.
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This method is called right before this thread is started and this
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object’s run() method is invoked.
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"""
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pass
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def start(self):
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self.on_thread_start()
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threading.Thread.start(self)
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def load_module(module_name):
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"""Imports a module given its name and returns a handle to it."""
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try:
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__import__(module_name)
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except ImportError:
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raise ImportError(f"No module named {module_name}")
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return sys.modules[module_name]
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def load_class(dotted_path):
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"""Loads and returns a class definition provided a dotted path
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specification the last part of the dotted path is the class name
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and there is at least one module name preceding the class name.
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Notes:
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You will need to ensure that the module you are trying to load
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exists in the Python path.
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Examples:
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- module.name.ClassName # Provided module.name is in the Python path.
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- module.ClassName # Provided module is in the Python path.
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What won't work:
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- ClassName
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- modle.name.ClassName # Typo in module name.
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- module.name.ClasNam # Typo in classname.
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"""
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dotted_path_split = dotted_path.split(".")
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if len(dotted_path_split) <= 1:
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raise ValueError(
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f"Dotted module path {dotted_path} must contain a module name and a classname"
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)
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klass_name = dotted_path_split[-1]
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module_name = ".".join(dotted_path_split[:-1])
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module = load_module(module_name)
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if hasattr(module, klass_name):
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return getattr(module, klass_name)
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# Finally create and return an instance of the class
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# return klass(*args, **kwargs)
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else:
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raise AttributeError(
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f"Module {module_name} does not have class attribute {klass_name}"
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)
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if TYPE_CHECKING or sys.version_info >= (3, 8):
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# using `as` to explicitly re-export this since this is a compatibility layer
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from typing import Protocol as Protocol
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else:
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# Provide a dummy Protocol class when not available from stdlib. Should be used
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# only for hinting. This could be had from typing_protocol, but not worth adding
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# the _first_ dependency just for this.
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class Protocol:
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...
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