370 lines
11 KiB
Python
370 lines
11 KiB
Python
#!/usr/bin/env python
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# -*- coding: utf-8 -*-
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#
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# Copyright 2011 Yesudeep Mangalapilly <yesudeep@gmail.com>
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# Copyright 2012 Google, Inc.
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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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from __future__ import with_statement
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import threading
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from ..utils import BaseThread
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from ..utils.compat import queue
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from ..utils.bricks import SkipRepeatsQueue
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DEFAULT_EMITTER_TIMEOUT = 1 # in seconds.
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DEFAULT_OBSERVER_TIMEOUT = 1 # in seconds.
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# Collection classes
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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(object):
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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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"""
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def __init__(self, path, recursive):
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self._path = path
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self._is_recursive = recursive
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@property
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def path(self):
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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):
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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 key(self):
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return self.path, self.is_recursive
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def __eq__(self, watch):
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return self.key == watch.key
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def __ne__(self, watch):
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return self.key != watch.key
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def __hash__(self):
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return hash(self.key)
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def __repr__(self):
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return "<ObservedWatch: path=%s, is_recursive=%s>" % (
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self.path, self.is_recursive)
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# Observer classes
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class EventEmitter(BaseThread):
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"""
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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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"""
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def __init__(self, event_queue, watch, timeout=DEFAULT_EMITTER_TIMEOUT):
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BaseThread.__init__(self)
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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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@property
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def timeout(self):
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"""
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Blocking timeout for reading events.
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"""
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return self._timeout
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@property
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def watch(self):
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"""
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The watch associated with this emitter.
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"""
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return self._watch
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def queue_event(self, event):
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"""
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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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self._event_queue.put((event, self.watch))
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def queue_events(self, timeout):
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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):
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try:
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while self.should_keep_running():
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self.queue_events(self.timeout)
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finally:
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pass
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class EventDispatcher(BaseThread):
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"""
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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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Event queue blocking timeout (in seconds).
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:type timeout:
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``float``
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"""
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def __init__(self, timeout=DEFAULT_OBSERVER_TIMEOUT):
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BaseThread.__init__(self)
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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):
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"""Event queue block timeout."""
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return self._timeout
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@property
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def event_queue(self):
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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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return self._event_queue
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def dispatch_events(self, event_queue, timeout):
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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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:param timeout:
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Interval period (in seconds) to wait before timing out on the
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event queue.
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:type timeout:
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``float``
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:raises:
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:class:`queue.Empty`
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"""
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def run(self):
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while self.should_keep_running():
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try:
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self.dispatch_events(self.event_queue, self.timeout)
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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, timeout=DEFAULT_OBSERVER_TIMEOUT):
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EventDispatcher.__init__(self, 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()
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self._handlers = dict()
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self._emitters = set()
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self._emitter_for_watch = dict()
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def _add_emitter(self, emitter):
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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):
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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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try:
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emitter.join()
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except RuntimeError:
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pass
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def _clear_emitters(self):
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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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try:
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emitter.join()
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except RuntimeError:
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pass
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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, watch):
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if watch not in self._handlers:
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self._handlers[watch] = set()
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self._handlers[watch].add(event_handler)
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def _remove_handlers_for_watch(self, watch):
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del self._handlers[watch]
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@property
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def emitters(self):
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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):
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for emitter in self._emitters:
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emitter.start()
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super(BaseObserver, self).start()
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def schedule(self, event_handler, path, recursive=False):
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"""
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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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: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)
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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 self._emitter_for_watch.get(watch) is None:
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emitter = self._emitter_class(event_queue=self.event_queue,
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watch=watch,
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timeout=self.timeout)
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self._add_emitter(emitter)
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if self.is_alive():
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emitter.start()
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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, watch):
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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, watch):
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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):
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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):
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"""Unschedules all watches and detaches all associated event
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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):
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self.unschedule_all()
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def dispatch_events(self, event_queue, timeout):
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event, watch = event_queue.get(block=True, timeout=timeout)
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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 list(self._handlers.get(watch, [])):
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if handler in self._handlers.get(watch, []):
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handler.dispatch(event)
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event_queue.task_done()
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