393 lines
14 KiB
Python
393 lines
14 KiB
Python
from __future__ import annotations
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import contextlib
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import queue
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import threading
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from collections import defaultdict
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from pathlib import Path
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from typing import TYPE_CHECKING
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from watchdog.utils import BaseThread
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from watchdog.utils.bricks import SkipRepeatsQueue
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if TYPE_CHECKING:
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from watchdog.events import FileSystemEvent, FileSystemEventHandler
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DEFAULT_EMITTER_TIMEOUT = 1.0 # in seconds
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DEFAULT_OBSERVER_TIMEOUT = 1.0 # in seconds
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class EventQueue(SkipRepeatsQueue):
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"""Thread-safe event queue based on a special queue that skips adding
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the same event (:class:`FileSystemEvent`) multiple times consecutively.
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Thus avoiding dispatching multiple event handling
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calls when multiple identical events are produced quicker than an observer
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can consume them.
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"""
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class ObservedWatch:
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"""An scheduled watch.
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:param path:
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Path string.
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:param recursive:
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``True`` if watch is recursive; ``False`` otherwise.
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:param event_filter:
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Optional collection of :class:`watchdog.events.FileSystemEvent` to watch
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"""
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def __init__(self, path: str | Path, *, recursive: bool, event_filter: list[type[FileSystemEvent]] | None = None):
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self._path = str(path) if isinstance(path, Path) else path
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self._is_recursive = recursive
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self._event_filter = frozenset(event_filter) if event_filter is not None else None
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@property
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def path(self) -> str:
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"""The path that this watch monitors."""
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return self._path
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@property
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def is_recursive(self) -> bool:
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"""Determines whether subdirectories are watched for the path."""
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return self._is_recursive
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@property
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def event_filter(self) -> frozenset[type[FileSystemEvent]] | None:
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"""Collection of event types watched for the path"""
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return self._event_filter
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@property
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def key(self) -> tuple[str, bool, frozenset[type[FileSystemEvent]] | None]:
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return self.path, self.is_recursive, self.event_filter
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def __eq__(self, watch: object) -> bool:
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if not isinstance(watch, ObservedWatch):
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return NotImplemented
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return self.key == watch.key
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def __ne__(self, watch: object) -> bool:
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if not isinstance(watch, ObservedWatch):
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return NotImplemented
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return self.key != watch.key
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def __hash__(self) -> int:
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return hash(self.key)
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def __repr__(self) -> str:
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if self.event_filter is not None:
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event_filter_str = "|".join(sorted(_cls.__name__ for _cls in self.event_filter))
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event_filter_str = f", event_filter={event_filter_str}"
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else:
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event_filter_str = ""
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return f"<{type(self).__name__}: path={self.path!r}, is_recursive={self.is_recursive}{event_filter_str}>"
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# Observer classes
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class EventEmitter(BaseThread):
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"""Producer thread base class subclassed by event emitters
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that generate events and populate a queue with them.
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:param event_queue:
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The event queue to populate with generated events.
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:type event_queue:
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:class:`watchdog.events.EventQueue`
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:param watch:
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The watch to observe and produce events for.
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:type watch:
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:class:`ObservedWatch`
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:param timeout:
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Timeout (in seconds) between successive attempts at reading events.
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:type timeout:
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``float``
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:param event_filter:
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Collection of event types to emit, or None for no filtering (default).
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:type event_filter:
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Iterable[:class:`watchdog.events.FileSystemEvent`] | None
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"""
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def __init__(
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self,
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event_queue: EventQueue,
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watch: ObservedWatch,
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*,
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timeout: float = DEFAULT_EMITTER_TIMEOUT,
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event_filter: list[type[FileSystemEvent]] | None = None,
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) -> None:
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super().__init__()
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self._event_queue = event_queue
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self._watch = watch
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self._timeout = timeout
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self._event_filter = frozenset(event_filter) if event_filter is not None else None
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@property
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def timeout(self) -> float:
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"""Blocking timeout for reading events."""
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return self._timeout
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@property
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def watch(self) -> ObservedWatch:
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"""The watch associated with this emitter."""
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return self._watch
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def queue_event(self, event: FileSystemEvent) -> None:
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"""Queues a single event.
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:param event:
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Event to be queued.
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:type event:
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An instance of :class:`watchdog.events.FileSystemEvent`
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or a subclass.
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"""
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if self._event_filter is None or any(isinstance(event, cls) for cls in self._event_filter):
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self._event_queue.put((event, self.watch))
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def queue_events(self, timeout: float) -> None:
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"""Override this method to populate the event queue with events
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per interval period.
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:param timeout:
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Timeout (in seconds) between successive attempts at
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reading events.
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:type timeout:
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``float``
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"""
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def run(self) -> None:
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while self.should_keep_running():
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self.queue_events(self.timeout)
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class EventDispatcher(BaseThread):
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"""Consumer thread base class subclassed by event observer threads
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that dispatch events from an event queue to appropriate event handlers.
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:param timeout:
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Timeout value (in seconds) passed to emitters
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constructions in the child class BaseObserver.
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:type timeout:
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``float``
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"""
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stop_event = object()
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"""Event inserted into the queue to signal a requested stop."""
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def __init__(self, *, timeout: float = DEFAULT_OBSERVER_TIMEOUT) -> None:
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super().__init__()
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self._event_queue = EventQueue()
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self._timeout = timeout
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@property
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def timeout(self) -> float:
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"""Timeout value to construct emitters with."""
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return self._timeout
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def stop(self) -> None:
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BaseThread.stop(self)
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with contextlib.suppress(queue.Full):
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self.event_queue.put_nowait(EventDispatcher.stop_event)
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@property
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def event_queue(self) -> EventQueue:
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"""The event queue which is populated with file system events
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by emitters and from which events are dispatched by a dispatcher
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thread.
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"""
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return self._event_queue
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def dispatch_events(self, event_queue: EventQueue) -> None:
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"""Override this method to consume events from an event queue, blocking
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on the queue for the specified timeout before raising :class:`queue.Empty`.
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:param event_queue:
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Event queue to populate with one set of events.
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:type event_queue:
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:class:`EventQueue`
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:raises:
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:class:`queue.Empty`
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"""
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def run(self) -> None:
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while self.should_keep_running():
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try:
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self.dispatch_events(self.event_queue)
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except queue.Empty:
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continue
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class BaseObserver(EventDispatcher):
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"""Base observer."""
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def __init__(self, emitter_class: type[EventEmitter], *, timeout: float = DEFAULT_OBSERVER_TIMEOUT) -> None:
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super().__init__(timeout=timeout)
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self._emitter_class = emitter_class
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self._lock = threading.RLock()
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self._watches: set[ObservedWatch] = set()
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self._handlers: defaultdict[ObservedWatch, set[FileSystemEventHandler]] = defaultdict(set)
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self._emitters: set[EventEmitter] = set()
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self._emitter_for_watch: dict[ObservedWatch, EventEmitter] = {}
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def _add_emitter(self, emitter: EventEmitter) -> None:
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self._emitter_for_watch[emitter.watch] = emitter
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self._emitters.add(emitter)
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def _remove_emitter(self, emitter: EventEmitter) -> None:
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del self._emitter_for_watch[emitter.watch]
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self._emitters.remove(emitter)
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emitter.stop()
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with contextlib.suppress(RuntimeError):
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emitter.join()
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def _clear_emitters(self) -> None:
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for emitter in self._emitters:
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emitter.stop()
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for emitter in self._emitters:
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with contextlib.suppress(RuntimeError):
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emitter.join()
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self._emitters.clear()
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self._emitter_for_watch.clear()
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def _add_handler_for_watch(self, event_handler: FileSystemEventHandler, watch: ObservedWatch) -> None:
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self._handlers[watch].add(event_handler)
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def _remove_handlers_for_watch(self, watch: ObservedWatch) -> None:
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del self._handlers[watch]
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@property
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def emitters(self) -> set[EventEmitter]:
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"""Returns event emitter created by this observer."""
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return self._emitters
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def start(self) -> None:
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for emitter in self._emitters.copy():
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try:
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emitter.start()
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except Exception:
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self._remove_emitter(emitter)
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raise
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super().start()
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def schedule(
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self,
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event_handler: FileSystemEventHandler,
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path: str,
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*,
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recursive: bool = False,
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event_filter: list[type[FileSystemEvent]] | None = None,
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) -> ObservedWatch:
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"""Schedules watching a path and calls appropriate methods specified
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in the given event handler in response to file system events.
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:param event_handler:
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An event handler instance that has appropriate event handling
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methods which will be called by the observer in response to
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file system events.
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:type event_handler:
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:class:`watchdog.events.FileSystemEventHandler` or a subclass
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:param path:
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Directory path that will be monitored.
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:type path:
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``str``
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:param recursive:
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``True`` if events will be emitted for sub-directories
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traversed recursively; ``False`` otherwise.
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:type recursive:
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``bool``
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:param event_filter:
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Collection of event types to emit, or None for no filtering (default).
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:type event_filter:
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Iterable[:class:`watchdog.events.FileSystemEvent`] | None
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:return:
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An :class:`ObservedWatch` object instance representing
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a watch.
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"""
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with self._lock:
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watch = ObservedWatch(path, recursive=recursive, event_filter=event_filter)
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self._add_handler_for_watch(event_handler, watch)
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# If we don't have an emitter for this watch already, create it.
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if watch not in self._emitter_for_watch:
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emitter = self._emitter_class(self.event_queue, watch, timeout=self.timeout, event_filter=event_filter)
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if self.is_alive():
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emitter.start()
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self._add_emitter(emitter)
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self._watches.add(watch)
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return watch
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def add_handler_for_watch(self, event_handler: FileSystemEventHandler, watch: ObservedWatch) -> None:
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"""Adds a handler for the given watch.
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:param event_handler:
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An event handler instance that has appropriate event handling
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methods which will be called by the observer in response to
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file system events.
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:type event_handler:
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:class:`watchdog.events.FileSystemEventHandler` or a subclass
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:param watch:
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The watch to add a handler for.
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:type watch:
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An instance of :class:`ObservedWatch` or a subclass of
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:class:`ObservedWatch`
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"""
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with self._lock:
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self._add_handler_for_watch(event_handler, watch)
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def remove_handler_for_watch(self, event_handler: FileSystemEventHandler, watch: ObservedWatch) -> None:
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"""Removes a handler for the given watch.
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:param event_handler:
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An event handler instance that has appropriate event handling
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methods which will be called by the observer in response to
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file system events.
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:type event_handler:
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:class:`watchdog.events.FileSystemEventHandler` or a subclass
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:param watch:
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The watch to remove a handler for.
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:type watch:
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An instance of :class:`ObservedWatch` or a subclass of
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:class:`ObservedWatch`
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"""
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with self._lock:
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self._handlers[watch].remove(event_handler)
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def unschedule(self, watch: ObservedWatch) -> None:
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"""Unschedules a watch.
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:param watch:
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The watch to unschedule.
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:type watch:
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An instance of :class:`ObservedWatch` or a subclass of
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:class:`ObservedWatch`
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"""
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with self._lock:
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emitter = self._emitter_for_watch[watch]
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del self._handlers[watch]
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self._remove_emitter(emitter)
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self._watches.remove(watch)
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def unschedule_all(self) -> None:
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"""Unschedules all watches and detaches all associated event handlers."""
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with self._lock:
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self._handlers.clear()
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self._clear_emitters()
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self._watches.clear()
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def on_thread_stop(self) -> None:
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self.unschedule_all()
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def dispatch_events(self, event_queue: EventQueue) -> None:
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entry = event_queue.get(block=True)
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if entry is EventDispatcher.stop_event:
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return
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event, watch = entry
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with self._lock:
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# To allow unschedule/stop and safe removal of event handlers
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# within event handlers itself, check if the handler is still
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# registered after every dispatch.
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for handler in self._handlers[watch].copy():
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if handler in self._handlers[watch]:
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handler.dispatch(event)
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event_queue.task_done()
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