4 # Copyright (C) 2009 Google Inc.
6 # This program is free software; you can redistribute it and/or modify
7 # it under the terms of the GNU General Public License as published by
8 # the Free Software Foundation; either version 2 of the License, or
9 # (at your option) any later version.
11 # This program is distributed in the hope that it will be useful, but
12 # WITHOUT ANY WARRANTY; without even the implied warranty of
13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 # General Public License for more details.
16 # You should have received a copy of the GNU General Public License
17 # along with this program; if not, write to the Free Software
18 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
22 """Asynchronous pyinotify implementation"""
29 # pylint: disable-msg=E0611
30 from pyinotify import pyinotify
34 from ganeti import errors
36 # We contributed the AsyncNotifier class back to python-pyinotify, and it's
37 # part of their codebase since version 0.8.7. This code can be removed once
38 # we'll be ready to depend on python-pyinotify >= 0.8.7
39 class AsyncNotifier(asyncore.file_dispatcher):
40 """An asyncore dispatcher for inotify events.
43 # pylint: disable-msg=W0622,W0212
44 def __init__(self, watch_manager, default_proc_fun=None, map=None):
45 """Initializes this class.
47 This is a a special asyncore file_dispatcher that actually wraps a
48 pyinotify Notifier, making it asyncronous.
51 if default_proc_fun is None:
52 default_proc_fun = pyinotify.ProcessEvent()
54 self.notifier = pyinotify.Notifier(watch_manager, default_proc_fun)
56 # here we need to steal the file descriptor from the notifier, so we can
57 # use it in the global asyncore select, and avoid calling the
58 # check_events() function of the notifier (which doesn't allow us to select
59 # together with other file descriptors)
60 self.fd = self.notifier._fd
61 asyncore.file_dispatcher.__init__(self, self.fd, map)
63 def handle_read(self):
64 self.notifier.read_events()
65 self.notifier.process_events()
68 class SingleFileEventHandler(pyinotify.ProcessEvent):
69 """Handle modify events for a single file.
73 def __init__(self, watch_manager, callback, filename):
74 """Constructor for SingleFileEventHandler
76 @type watch_manager: pyinotify.WatchManager
77 @param watch_manager: inotify watch manager
78 @type callback: function accepting a boolean
79 @param callback: function to call when an inotify event happens
80 @type filename: string
81 @param filename: config file to watch
84 # pylint: disable-msg=W0231
85 # no need to call the parent's constructor
86 self.watch_manager = watch_manager
87 self.callback = callback
88 self.mask = pyinotify.EventsCodes.ALL_FLAGS["IN_IGNORED"] | \
89 pyinotify.EventsCodes.ALL_FLAGS["IN_MODIFY"]
91 self.watch_handle = None
94 """Watch the given file
97 if self.watch_handle is None:
98 result = self.watch_manager.add_watch(self.file, self.mask)
99 if not self.file in result or result[self.file] <= 0:
100 raise errors.InotifyError("Could not add inotify watcher")
102 self.watch_handle = result[self.file]
105 """Stop watching the given file
108 if self.watch_handle is not None:
109 result = self.watch_manager.rm_watch(self.watch_handle)
110 if result[self.watch_handle]:
111 self.watch_handle = None
113 # pylint: disable-msg=C0103
114 # this overrides a method in pyinotify.ProcessEvent
115 def process_IN_IGNORED(self, event):
116 # Due to the fact that we monitor just for the cluster config file (rather
117 # than for the whole data dir) when the file is replaced with another one
118 # (which is what happens normally in ganeti) we're going to receive an
119 # IN_IGNORED event from inotify, because of the file removal (which is
120 # contextual with the replacement). In such a case we need to create
121 # another watcher for the "new" file.
122 logging.debug("Received 'ignored' inotify event for %s", event.path)
123 self.watch_handle = None
126 # Since the kernel believes the file we were interested in is gone, it's
127 # not going to notify us of any other events, until we set up, here, the
128 # new watch. This is not a race condition, though, since we're anyway
129 # going to realod the file after setting up the new watch.
131 except: # pylint: disable-msg=W0702
132 # we need to catch any exception here, log it, but proceed, because even
133 # if we failed handling a single request, we still want our daemon to
135 logging.error("Unexpected exception", exc_info=True)
137 # pylint: disable-msg=C0103
138 # this overrides a method in pyinotify.ProcessEvent
139 def process_IN_MODIFY(self, event):
140 # This gets called when the config file is modified. Note that this doesn't
141 # usually happen in Ganeti, as the config file is normally replaced by a
142 # new one, at filesystem level, rather than actually modified (see
144 logging.debug("Received 'modify' inotify event for %s", event.path)
148 except: # pylint: disable-msg=W0702
149 # we need to catch any exception here, log it, but proceed, because even
150 # if we failed handling a single request, we still want our daemon to
152 logging.error("Unexpected exception", exc_info=True)
154 def process_default(self, event):
155 logging.error("Received unhandled inotify event: %s", event)