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# 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.
import abc
import atexit
import itertools
import logging
import queue
import threading
# Several supported distros don't package sortedcontainers. For this reason
# python-ovs, which requires it for indexing support, has an in-tree copy of
# it. We already require sortedcontainers through python-ovs' dependency, so
# to avoid issues with distro packaging, we don't add sortedcontainers as a
# hard direct requirement of ovsdbapp, and use python-ovs' if it is missing.
try:
import sortedcontainers
except ImportError:
from ovs.compat import sortedcontainers
LOG = logging.getLogger(__name__)
STOP_EVENT = ("STOP", None, None, None)
class RowEvent(object, metaclass=abc.ABCMeta):
ROW_CREATE = "create"
ROW_UPDATE = "update"
ROW_DELETE = "delete"
ONETIME = False
event_name = 'RowEvent'
priority = 20
def __init__(self, events, table, conditions, old_conditions=None):
self.table = table
self.events = events
self.conditions = conditions
self.old_conditions = old_conditions
@property
def key(self):
return (self.__class__, self.table, tuple(self.events))
def __hash__(self):
return hash(self.key)
def __eq__(self, other):
try:
return (self.key == other.key and
self.conditions == other.conditions and
self.priority == other.priority)
except AttributeError:
return False
def __ne__(self, other):
return not self == other
def __repr__(self):
return ("%s(events=%r, table=%r, conditions=%r, old_conditions=%r), "
"priority=%d" %
(self.__class__.__name__, self.events,
self.table, self.conditions, self.old_conditions,
self.priority))
@abc.abstractmethod
def matches(self, event, row, old=None):
"""Test that `event` on `row` matches watched events
:param event: event type
:type event: ROW_CREATE, ROW_UPDATE, or ROW_DELETE
:param row:
:param old:
:returns: boolean, True if match else False
"""
@abc.abstractmethod
def run(self, event, row, old):
"""Method to run when the event matches"""
class WaitEvent(RowEvent):
event_name = 'WaitEvent'
ONETIME = True
priority = 10
def __init__(self, *args, **kwargs):
self.event = threading.Event()
self.timeout = kwargs.pop('timeout', None)
super().__init__(*args, **kwargs)
@abc.abstractmethod
def matches(self, event, row, old=None):
"""Test that `event on `row` matches watched events. See: RowEvent"""
def run(self, event, row, old):
self.event.set()
def wait(self):
return self.event.wait(self.timeout)
class RowEventHandler(object):
def __init__(self):
self._queues = sortedcontainers.SortedDict(lambda p: -p)
self._lock = threading.Lock()
self.notifications = queue.Queue()
self.notify_thread = threading.Thread(target=self.notify_loop)
self.notify_thread.daemon = True
atexit.register(self.shutdown)
self.start()
def start(self):
self.notify_thread.start()
def _get_queue(self, event):
return self._queues.setdefault(event.priority, set())
@property
def _watched_events(self):
return itertools.chain(*self._queues.values())
def _add(self, event):
self._get_queue(event).add(event)
def _discard(self, event):
self._get_queue(event).discard(event)
@staticmethod
def match(candidate, event, row, updates):
try:
return candidate.matches(event, row, updates)
except Exception:
LOG.exception("Event not matched due to this exception:\n")
return False
def matching_events(self, event, row, updates):
with self._lock:
return tuple(t for t in self._watched_events
if self.match(t, event, row, updates))
def watch_event(self, event):
with self._lock:
self._add(event)
def watch_events(self, events):
with self._lock:
for event in events:
self._add(event)
def unwatch_event(self, event):
with self._lock:
self._discard(event)
def unwatch_events(self, events):
with self._lock:
for event in events:
self._discard(event)
def shutdown(self):
self.notifications.put(STOP_EVENT)
def notify_loop(self):
while True:
try:
match, event, row, updates = self.notifications.get()
if (match, event, row, updates) == STOP_EVENT:
self.notifications.task_done()
break
match.run(event, row, updates)
if match.ONETIME:
self.unwatch_event(match)
self.notifications.task_done()
except Exception:
# If any unexpected exception happens we don't want the
# notify_loop to exit.
LOG.exception('Unexpected exception in notify_loop')
def notify(self, event, row, updates=None):
"""Method for calling backend to call for each DB update
:param event: Backend representation of event type, e.g.
create, update, delete
:param row: Backend representation of a Row object. If it is not
immutable, it should be converted or guaranteed not to
be changed in other threads.
:param updates: Backend representation of updates to a Row. e.g.
a Row object with just changed attributes, a
dictionary of changes, etc.
"""
matching = self.matching_events(
event, row, updates)
for match in matching:
self.notifications.put((match, event, row, updates))
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