# coding: utf-8 # # Copyright 2011 Yesudeep Mangalapilly # Copyright 2012 Google, Inc & contributors. # # 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. """ :module: watchdog.observers.kqueue :synopsis: ``kqueue(2)`` based emitter implementation. :author: yesudeep@google.com (Yesudeep Mangalapilly) :author: contact@tiger-222.fr (Mickaël Schoentgen) :platforms: Mac OS X and BSD with kqueue(2). .. WARNING:: kqueue is a very heavyweight way to monitor file systems. Each kqueue-detected directory modification triggers a full directory scan. Traversing the entire directory tree and opening file descriptors for all files will create performance problems. We need to find a way to re-scan only those directories which report changes and do a diff between two sub-DirectorySnapshots perhaps. .. ADMONITION:: About OS X performance guidelines Quote from the `Mac OS X File System Performance Guidelines`_: "When you only want to track changes on a file or directory, be sure to open it using the ``O_EVTONLY`` flag. This flag prevents the file or directory from being marked as open or in use. This is important if you are tracking files on a removable volume and the user tries to unmount the volume. With this flag in place, the system knows it can dismiss the volume. If you had opened the files or directories without this flag, the volume would be marked as busy and would not be unmounted." ``O_EVTONLY`` is defined as ``0x8000`` in the OS X header files. More information here: http://www.mlsite.net/blog/?p=2312 Classes ------- .. autoclass:: KqueueEmitter :members: :show-inheritance: Collections and Utility Classes ------------------------------- .. autoclass:: KeventDescriptor :members: :show-inheritance: .. autoclass:: KeventDescriptorSet :members: :show-inheritance: .. _Mac OS X File System Performance Guidelines: http://developer.apple.com/library/ios/#documentation/Performance/Conceptual/FileSystem/Articles/TrackingChanges.html#//apple_ref/doc/uid/20001993-CJBJFIDD """ from ..utils import platform import threading import errno from stat import S_ISDIR import os import os.path import select from pathlib import Path from .api import ( BaseObserver, EventEmitter, DEFAULT_OBSERVER_TIMEOUT, DEFAULT_EMITTER_TIMEOUT ) from ..utils.dirsnapshot import DirectorySnapshot from ..events import ( DirMovedEvent, DirDeletedEvent, DirCreatedEvent, DirModifiedEvent, FileMovedEvent, FileDeletedEvent, FileCreatedEvent, FileModifiedEvent, EVENT_TYPE_MOVED, EVENT_TYPE_DELETED, EVENT_TYPE_CREATED, generate_sub_moved_events, ) # Maximum number of events to process. MAX_EVENTS = 4096 # O_EVTONLY value from the header files for OS X only. O_EVTONLY = 0x8000 # Pre-calculated values for the kevent filter, flags, and fflags attributes. if platform.is_darwin(): WATCHDOG_OS_OPEN_FLAGS = O_EVTONLY else: WATCHDOG_OS_OPEN_FLAGS = os.O_RDONLY | os.O_NONBLOCK WATCHDOG_KQ_FILTER = select.KQ_FILTER_VNODE WATCHDOG_KQ_EV_FLAGS = select.KQ_EV_ADD | select.KQ_EV_ENABLE | select.KQ_EV_CLEAR WATCHDOG_KQ_FFLAGS = ( select.KQ_NOTE_DELETE | select.KQ_NOTE_WRITE | select.KQ_NOTE_EXTEND | select.KQ_NOTE_ATTRIB | select.KQ_NOTE_LINK | select.KQ_NOTE_RENAME | select.KQ_NOTE_REVOKE ) def absolute_path(path): return Path(path).resolve() # Flag tests. def is_deleted(kev): """Determines whether the given kevent represents deletion.""" return kev.fflags & select.KQ_NOTE_DELETE def is_modified(kev): """Determines whether the given kevent represents modification.""" fflags = kev.fflags return (fflags & select.KQ_NOTE_EXTEND) or (fflags & select.KQ_NOTE_WRITE) def is_attrib_modified(kev): """Determines whether the given kevent represents attribute modification.""" return kev.fflags & select.KQ_NOTE_ATTRIB def is_renamed(kev): """Determines whether the given kevent represents movement.""" return kev.fflags & select.KQ_NOTE_RENAME class KeventDescriptorSet: """ Thread-safe kevent descriptor collection. """ def __init__(self): # Set of KeventDescriptor self._descriptors = set() # Descriptor for a given path. self._descriptor_for_path = dict() # Descriptor for a given fd. self._descriptor_for_fd = dict() # List of kevent objects. self._kevents = list() self._lock = threading.Lock() @property def kevents(self): """ List of kevents monitored. """ with self._lock: return self._kevents @property def paths(self): """ List of paths for which kevents have been created. """ with self._lock: return list(self._descriptor_for_path.keys()) def get_for_fd(self, fd): """ Given a file descriptor, returns the kevent descriptor object for it. :param fd: OS file descriptor. :type fd: ``int`` :returns: A :class:`KeventDescriptor` object. """ with self._lock: return self._descriptor_for_fd[fd] def get(self, path): """ Obtains a :class:`KeventDescriptor` object for the specified path. :param path: Path for which the descriptor will be obtained. """ with self._lock: path = absolute_path(path) return self._get(path) def __contains__(self, path): """ Determines whether a :class:`KeventDescriptor has been registered for the specified path. :param path: Path for which the descriptor will be obtained. """ with self._lock: path = absolute_path(path) return self._has_path(path) def add(self, path, is_directory): """ Adds a :class:`KeventDescriptor` to the collection for the given path. :param path: The path for which a :class:`KeventDescriptor` object will be added. :param is_directory: ``True`` if the path refers to a directory; ``False`` otherwise. :type is_directory: ``bool`` """ with self._lock: path = absolute_path(path) if not self._has_path(path): self._add_descriptor(KeventDescriptor(path, is_directory)) def remove(self, path): """ Removes the :class:`KeventDescriptor` object for the given path if it already exists. :param path: Path for which the :class:`KeventDescriptor` object will be removed. """ with self._lock: path = absolute_path(path) if self._has_path(path): self._remove_descriptor(self._get(path)) def clear(self): """ Clears the collection and closes all open descriptors. """ with self._lock: for descriptor in self._descriptors: descriptor.close() self._descriptors.clear() self._descriptor_for_fd.clear() self._descriptor_for_path.clear() self._kevents = [] # Thread-unsafe methods. Locking is provided at a higher level. def _get(self, path): """Returns a kevent descriptor for a given path.""" return self._descriptor_for_path[path] def _has_path(self, path): """Determines whether a :class:`KeventDescriptor` for the specified path exists already in the collection.""" return path in self._descriptor_for_path def _add_descriptor(self, descriptor): """ Adds a descriptor to the collection. :param descriptor: An instance of :class:`KeventDescriptor` to be added. """ self._descriptors.add(descriptor) self._kevents.append(descriptor.kevent) self._descriptor_for_path[descriptor.path] = descriptor self._descriptor_for_fd[descriptor.fd] = descriptor def _remove_descriptor(self, descriptor): """ Removes a descriptor from the collection. :param descriptor: An instance of :class:`KeventDescriptor` to be removed. """ self._descriptors.remove(descriptor) del self._descriptor_for_fd[descriptor.fd] del self._descriptor_for_path[descriptor.path] self._kevents.remove(descriptor.kevent) descriptor.close() class KeventDescriptor: """ A kevent descriptor convenience data structure to keep together: * kevent * directory status * path * file descriptor :param path: Path string for which a kevent descriptor will be created. :param is_directory: ``True`` if the path refers to a directory; ``False`` otherwise. :type is_directory: ``bool`` """ def __init__(self, path, is_directory): self._path = absolute_path(path) self._is_directory = is_directory self._fd = os.open(path, WATCHDOG_OS_OPEN_FLAGS) self._kev = select.kevent(self._fd, filter=WATCHDOG_KQ_FILTER, flags=WATCHDOG_KQ_EV_FLAGS, fflags=WATCHDOG_KQ_FFLAGS) @property def fd(self): """OS file descriptor for the kevent descriptor.""" return self._fd @property def path(self): """The path associated with the kevent descriptor.""" return self._path @property def kevent(self): """The kevent object associated with the kevent descriptor.""" return self._kev @property def is_directory(self): """Determines whether the kevent descriptor refers to a directory. :returns: ``True`` or ``False`` """ return self._is_directory def close(self): """ Closes the file descriptor associated with a kevent descriptor. """ try: os.close(self.fd) except OSError: pass @property def key(self): return (self.path, self.is_directory) def __eq__(self, descriptor): return self.key == descriptor.key def __ne__(self, descriptor): return self.key != descriptor.key def __hash__(self): return hash(self.key) def __repr__(self): return "<%s: path=%s, is_directory=%s>"\ % (type(self).__name__, self.path, self.is_directory) class KqueueEmitter(EventEmitter): """ kqueue(2)-based event emitter. .. ADMONITION:: About ``kqueue(2)`` behavior and this implementation ``kqueue(2)`` monitors file system events only for open descriptors, which means, this emitter does a lot of book-keeping behind the scenes to keep track of open descriptors for every entry in the monitored directory tree. This also means the number of maximum open file descriptors on your system must be increased **manually**. Usually, issuing a call to ``ulimit`` should suffice:: ulimit -n 1024 Ensure that you pick a number that is larger than the number of files you expect to be monitored. ``kqueue(2)`` does not provide enough information about the following things: * The destination path of a file or directory that is renamed. * Creation of a file or directory within a directory; in this case, ``kqueue(2)`` only indicates a modified event on the parent directory. Therefore, this emitter takes a snapshot of the directory tree when ``kqueue(2)`` detects a change on the file system to be able to determine the above information. :param event_queue: The event queue to fill with events. :param watch: A watch object representing the directory to monitor. :type watch: :class:`watchdog.observers.api.ObservedWatch` :param timeout: Read events blocking timeout (in seconds). :type timeout: ``float`` :param stat: stat function. See ``os.stat`` for details. """ def __init__(self, event_queue, watch, timeout=DEFAULT_EMITTER_TIMEOUT, stat=os.stat): EventEmitter.__init__(self, event_queue, watch, timeout) self._kq = select.kqueue() self._lock = threading.RLock() # A collection of KeventDescriptor. self._descriptors = KeventDescriptorSet() def custom_stat(path, self=self): stat_info = stat(path) self._register_kevent(path, S_ISDIR(stat_info.st_mode)) return stat_info self._snapshot = DirectorySnapshot(watch.path, recursive=watch.is_recursive, stat=custom_stat) def _register_kevent(self, path, is_directory): """ Registers a kevent descriptor for the given path. :param path: Path for which a kevent descriptor will be created. :param is_directory: ``True`` if the path refers to a directory; ``False`` otherwise. :type is_directory: ``bool`` """ try: self._descriptors.add(path, is_directory) except OSError as e: if e.errno == errno.ENOENT: # Probably dealing with a temporary file that was created # and then quickly deleted before we could open # a descriptor for it. Therefore, simply queue a sequence # of created and deleted events for the path. # path = absolute_path(path) # if is_directory: # self.queue_event(DirCreatedEvent(path)) # self.queue_event(DirDeletedEvent(path)) # else: # self.queue_event(FileCreatedEvent(path)) # self.queue_event(FileDeletedEvent(path)) # TODO: We could simply ignore these files. # Locked files cause the python process to die with # a bus error when we handle temporary files. # eg. .git/index.lock when running tig operations. # I don't fully understand this at the moment. pass elif e.errno == errno.EOPNOTSUPP: # Probably dealing with the socket or special file # mounted through a file system that does not support # access to it (e.g. NFS). On BSD systems look at # EOPNOTSUPP in man 2 open. pass else: # All other errors are propagated. raise def _unregister_kevent(self, path): """ Convenience function to close the kevent descriptor for a specified kqueue-monitored path. :param path: Path for which the kevent descriptor will be closed. """ self._descriptors.remove(path) def queue_event(self, event): """ Handles queueing a single event object. :param event: An instance of :class:`watchdog.events.FileSystemEvent` or a subclass. """ # Handles all the book keeping for queued events. # We do not need to fire moved/deleted events for all subitems in # a directory tree here, because this function is called by kqueue # for all those events anyway. EventEmitter.queue_event(self, event) if event.event_type == EVENT_TYPE_CREATED: self._register_kevent(event.src_path, event.is_directory) elif event.event_type == EVENT_TYPE_MOVED: self._unregister_kevent(event.src_path) self._register_kevent(event.dest_path, event.is_directory) elif event.event_type == EVENT_TYPE_DELETED: self._unregister_kevent(event.src_path) def _gen_kqueue_events(self, kev, ref_snapshot, new_snapshot): """ Generate events from the kevent list returned from the call to :meth:`select.kqueue.control`. .. NOTE:: kqueue only tells us about deletions, file modifications, attribute modifications. The other events, namely, file creation, directory modification, file rename, directory rename, directory creation, etc. are determined by comparing directory snapshots. """ descriptor = self._descriptors.get_for_fd(kev.ident) src_path = descriptor.path if is_renamed(kev): # Kqueue does not specify the destination names for renames # to, so we have to process these using the a snapshot # of the directory. for event in self._gen_renamed_events(src_path, descriptor.is_directory, ref_snapshot, new_snapshot): yield event elif is_attrib_modified(kev): if descriptor.is_directory: yield DirModifiedEvent(src_path) else: yield FileModifiedEvent(src_path) elif is_modified(kev): if descriptor.is_directory: if self.watch.is_recursive or self.watch.path == src_path: # When a directory is modified, it may be due to # sub-file/directory renames or new file/directory # creation. We determine all this by comparing # snapshots later. yield DirModifiedEvent(src_path) else: yield FileModifiedEvent(src_path) elif is_deleted(kev): if descriptor.is_directory: yield DirDeletedEvent(src_path) else: yield FileDeletedEvent(src_path) def _parent_dir_modified(self, src_path): """ Helper to generate a DirModifiedEvent on the parent of src_path. """ return DirModifiedEvent(os.path.dirname(src_path)) def _gen_renamed_events(self, src_path, is_directory, ref_snapshot, new_snapshot): """ Compares information from two directory snapshots (one taken before the rename operation and another taken right after) to determine the destination path of the file system object renamed, and yields the appropriate events to be queued. """ try: f_inode = ref_snapshot.inode(src_path) except KeyError: # Probably caught a temporary file/directory that was renamed # and deleted. Fires a sequence of created and deleted events # for the path. if is_directory: yield DirCreatedEvent(src_path) yield DirDeletedEvent(src_path) else: yield FileCreatedEvent(src_path) yield FileDeletedEvent(src_path) # We don't process any further and bail out assuming # the event represents deletion/creation instead of movement. return dest_path = new_snapshot.path(f_inode) if dest_path is not None: dest_path = absolute_path(dest_path) if is_directory: event = DirMovedEvent(src_path, dest_path) yield event else: yield FileMovedEvent(src_path, dest_path) yield self._parent_dir_modified(src_path) yield self._parent_dir_modified(dest_path) if is_directory: # TODO: Do we need to fire moved events for the items # inside the directory tree? Does kqueue does this # all by itself? Check this and then enable this code # only if it doesn't already. # A: It doesn't. So I've enabled this block. if self.watch.is_recursive: for sub_event in generate_sub_moved_events(src_path, dest_path): yield sub_event else: # If the new snapshot does not have an inode for the # old path, we haven't found the new name. Therefore, # we mark it as deleted and remove unregister the path. if is_directory: yield DirDeletedEvent(src_path) else: yield FileDeletedEvent(src_path) yield self._parent_dir_modified(src_path) def _read_events(self, timeout=None): """ Reads events from a call to the blocking :meth:`select.kqueue.control()` method. :param timeout: Blocking timeout for reading events. :type timeout: ``float`` (seconds) """ return self._kq.control(self._descriptors.kevents, MAX_EVENTS, timeout) def queue_events(self, timeout): """ Queues events by reading them from a call to the blocking :meth:`select.kqueue.control()` method. :param timeout: Blocking timeout for reading events. :type timeout: ``float`` (seconds) """ with self._lock: try: event_list = self._read_events(timeout) # TODO: investigate why order appears to be reversed event_list.reverse() # Take a fresh snapshot of the directory and update the # saved snapshot. new_snapshot = DirectorySnapshot(self.watch.path, self.watch.is_recursive) ref_snapshot = self._snapshot self._snapshot = new_snapshot diff_events = new_snapshot - ref_snapshot # Process events for directory_created in diff_events.dirs_created: self.queue_event(DirCreatedEvent(directory_created)) for file_created in diff_events.files_created: self.queue_event(FileCreatedEvent(file_created)) for file_modified in diff_events.files_modified: self.queue_event(FileModifiedEvent(file_modified)) for kev in event_list: for event in self._gen_kqueue_events(kev, ref_snapshot, new_snapshot): self.queue_event(event) except OSError as e: if e.errno != errno.EBADF: raise def on_thread_stop(self): # Clean up. with self._lock: self._descriptors.clear() self._kq.close() class KqueueObserver(BaseObserver): """ Observer thread that schedules watching directories and dispatches calls to event handlers. """ def __init__(self, timeout=DEFAULT_OBSERVER_TIMEOUT): BaseObserver.__init__(self, emitter_class=KqueueEmitter, timeout=timeout)