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| -rw-r--r-- | changes/next-changelog.rst | 1 | ||||
| -rw-r--r-- | src/leap/common/service_hooks.py | 75 |
2 files changed, 76 insertions, 0 deletions
diff --git a/changes/next-changelog.rst b/changes/next-changelog.rst index a1af28c..ba897df 100644 --- a/changes/next-changelog.rst +++ b/changes/next-changelog.rst @@ -10,6 +10,7 @@ I've added a new category `Misc` so we can track doc/style/packaging stuff. Features ~~~~~~~~ +- Add HookableService, allowing inter-service notification for hooks. - `#1234 <https://leap.se/code/issues/1234>`_: Description of the new feature corresponding with issue #1234. - New feature without related issue number. diff --git a/src/leap/common/service_hooks.py b/src/leap/common/service_hooks.py new file mode 100644 index 0000000..96e95cc --- /dev/null +++ b/src/leap/common/service_hooks.py @@ -0,0 +1,75 @@ +# -*- coding: utf-8 -*- +# service_hooks.py +# Copyright (C) 2016 LEAP +# +# This program is free software: you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation, either version 3 of the License, or +# (at your option) any later version. +# +# This program 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 General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see <http://www.gnu.org/licenses/>. +""" +Hooks for service composition. +""" +from collections import defaultdict + +from twisted.application.service import IService, Service +from twisted.python import log + +from zope.interface import implementer + + +@implementer(IService) +class HookableService(Service): + + """ + This service allows for other services in a Twisted Service tree to be + notified whenever a certain kind of hook is triggered. + + During the service composition, one is expected to register + a hook name with the name of the service that wants to react to the + triggering of the hook. All the services, both hooked and listeners, should + be registered against the same parent service. + + Upon the hook being triggered, the method "hook_<name>" will be called with + the passed data in the listener service. + """ + + def register_hook(self, name, listener): + if not hasattr(self, 'event_listeners'): + self.event_listeners = defaultdict(list) + log.msg("Registering hook %s->%s" % (name, listener)) + self.event_listeners[name].append(listener) + + def trigger_hook(self, name, **data): + + def react_to_hook(listener, name, **kw): + try: + getattr(listener, 'hook_' + name)(**kw) + except AttributeError: + raise RuntimeError( + "Tried to notify a hook, but the listener service class %s" + "has not defined the proper method" % listener.__class__) + + if not hasattr(self, 'event_listeners'): + self.event_listeners = defaultdict(list) + listeners = self._get_listener_services(name) + + for listener in listeners: + react_to_hook(listener, name, **data) + + def _get_sibling_service(self, name): + return self.parent.getServiceNamed(name) + + def _get_listener_services(self, hook): + if hook in self.event_listeners: + service_names = self.event_listeners[hook] + services = [ + self._get_sibling_service(name) for name in service_names] + return services |