def watch(self, key, **kwargs):
"""Watch a key.
:param key: key to watch
:returns: tuple of ``events_iterator`` and ``cancel``.
Use ``events_iterator`` to get the events of key changes
and ``cancel`` to cancel the watch request
"""
event_queue = queue.Queue()
def callback(event):
event_queue.put(event)
w = watch.Watcher(self, key, callback, **kwargs)
canceled = threading.Event()
def cancel():
canceled.set()
event_queue.put(None)
w.stop()
def iterator():
while not canceled.is_set():
event = event_queue.get()
if event is None:
canceled.set()
if not canceled.is_set():
yield event
return iterator(), cancel
def watch_once(self, key, timeout=None, **kwargs):
"""Watch a key and stops after the first event.
:param key: key to watch
:param timeout: (optional) timeout in seconds.
:returns: event
"""
event_queue = queue.Queue()
def callback(event):
event_queue.put(event)
w = watch.Watcher(self, key, callback, **kwargs)
try:
return event_queue.get(timeout=timeout)
except queue.Empty:
raise exceptions.WatchTimedOut()
finally:
w.stop()
