[repo] Add a publish/subscribe mechanism for inter-instance communication using zmq
Each repo can have a publishing and any number of subscribing sockets
whose addresses are specified in the instance's configuration. An
application or cube can subscribe to some 'topics', and give a callback
that gets called when a message matching that topic is received.
As a proof of concept, this introduces a hook to clean up the caches
associated with the repository when an entity is deleted.
A subscription is added using Repository::zmq::add_subscription;
the callback receives a list representing the received multi-part
message as argument (the first element of the message is its topic).
# -*- coding: utf-8 -*-
# copyright 2012 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
#
# This file is part of CubicWeb.
#
# CubicWeb is free software: you can redistribute it and/or modify it under the
# terms of the GNU Lesser General Public License as published by the Free
# Software Foundation, either version 2.1 of the License, or (at your option)
# any later version.
#
# CubicWeb is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
# details.
#
# You should have received a copy of the GNU Lesser General Public License along
# with CubicWeb. If not, see <http://www.gnu.org/licenses/>.
from cubicweb.server import hook
class ZMQStopHook(hook.Hook):
__regid__ = 'zmqstop'
events = ('server_shutdown',)
def __call__(self):
self.repo.app_instances_bus.stop()
class ZMQStartHook(hook.Hook):
__regid__ = 'zmqstart'
events = ('server_startup',)
def __call__(self):
config = self.repo.config
address_pub = config.get('zmq-address-pub')
if not address_pub:
return
from cubicweb.server import cwzmq
self.repo.app_instances_bus = cwzmq.ZMQComm()
self.repo.app_instances_bus.add_publisher(address_pub)
def clear_cache_callback(msg):
self.debug('clear_caches: %s', ' '.join(msg))
self.repo.clear_caches(msg[1:])
self.repo.app_instances_bus.add_subscription('delete', clear_cache_callback)
for address in config.get('zmq-address-sub'):
self.repo.app_instances_bus.add_subscriber(address)
self.repo.app_instances_bus.start()