152 lines
4.5 KiB
Python
152 lines
4.5 KiB
Python
# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# 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, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import abc
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import atexit
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import logging
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import threading
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import six
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from six.moves import queue as Queue
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LOG = logging.getLogger(__name__)
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STOP_EVENT = ("STOP", None, None, None)
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@six.add_metaclass(abc.ABCMeta)
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class RowEvent(object):
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ROW_CREATE = "create"
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ROW_UPDATE = "update"
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ROW_DELETE = "delete"
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ONETIME = False
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event_name = 'RowEvent'
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def __init__(self, events, table, conditions, old_conditions=None):
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self.table = table
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self.events = events
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self.conditions = conditions
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self.old_conditions = old_conditions
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@property
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def key(self):
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return (self.__class__, self.table, tuple(self.events))
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def __hash__(self):
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return hash(self.key)
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def __eq__(self, other):
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try:
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return (self.key == other.key and
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self.conditions == other.conditions)
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except AttributeError:
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return False
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def __ne__(self, other):
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return not self == other
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@abc.abstractmethod
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def matches(self, event, row, old=None):
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"""Test that `event` on `row` matches watched events
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:param event: event type
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:type event: ROW_CREATE, ROW_UPDATE, or ROW_DELETE
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:param row:
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:param old:
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:returns: boolean, True if match else False
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"""
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@abc.abstractmethod
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def run(self, event, row, old):
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"""Method to run when the event matches"""
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class WaitEvent(RowEvent):
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event_name = 'WaitEvent'
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ONETIME = True
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def __init__(self, *args, **kwargs):
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self.event = threading.Event()
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self.timeout = kwargs.pop('timeout', None)
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super(WaitEvent, self).__init__(*args, **kwargs)
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@abc.abstractmethod
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def matches(self, event, row, old=None):
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"""Test that `event on `row` matches watched events. See: RowEvent"""
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def run(self, event, row, old):
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self.event.set()
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def wait(self):
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return self.event.wait(self.timeout)
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class RowEventHandler(object):
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def __init__(self):
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self.__watched_events = set()
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self.__lock = threading.Lock()
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self.notifications = Queue.Queue()
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self.notify_thread = threading.Thread(target=self.notify_loop)
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self.notify_thread.daemon = True
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atexit.register(self.shutdown)
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self.start()
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def start(self):
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self.notify_thread.start()
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def matching_events(self, event, row, updates):
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with self.__lock:
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return tuple(t for t in self.__watched_events
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if t.matches(event, row, updates))
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def watch_event(self, event):
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with self.__lock:
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self.__watched_events.add(event)
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def watch_events(self, events):
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with self.__lock:
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for event in events:
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self.__watched_events.add(event)
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def unwatch_event(self, event):
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with self.__lock:
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self.__watched_events.discard(event)
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def unwatch_events(self, events):
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with self.__lock:
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for event in events:
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self.__watched_events.discard(event)
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def shutdown(self):
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self.notifications.put(STOP_EVENT)
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def notify_loop(self):
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while True:
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try:
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match, event, row, updates = self.notifications.get()
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if (match, event, row, updates) == STOP_EVENT:
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self.notifications.task_done()
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break
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match.run(event, row, updates)
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if match.ONETIME:
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self.unwatch_event(match)
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self.notifications.task_done()
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except Exception:
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# If any unexpected exception happens we don't want the
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# notify_loop to exit.
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LOG.exception('Unexpected exception in notify_loop')
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def notify(self, event, row, updates=None):
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matching = self.matching_events(
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event, row, updates)
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for match in matching:
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self.notifications.put((match, event, row, updates))
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