74f953a1d7
We don't need to have the vi modelines in each source file, it can be set in a user's vimrc if required. Also a check is added to hacking to detect if they are re-added. Change-Id: I347307a5145b2760c69085b6ca850d6a9137ffc6 Closes-Bug: #1229324
115 lines
3.4 KiB
Python
115 lines
3.4 KiB
Python
# Copyright (c) 2012 OpenStack Foundation
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# All Rights Reserved.
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#
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# 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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"""Decorator and config option definitions for adding custom code (hooks)
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around callables.
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Any method may have the 'add_hook' decorator applied, which yields the
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ability to invoke Hook objects before or after the method. (i.e. pre and
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post)
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Hook objects are loaded by HookLoaders. Each named hook may invoke multiple
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Hooks.
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Example Hook object:
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class MyHook(object):
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def pre(self, *args, **kwargs):
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# do stuff before wrapped callable runs
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def post(self, rv, *args, **kwargs):
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# do stuff after wrapped callable runs
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Example Hook object with function parameters:
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class MyHookWithFunction(object):
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def pre(self, f, *args, **kwargs):
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# do stuff with wrapped function info
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def post(self, f, *args, **kwards):
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# do stuff with wrapped function info
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"""
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import functools
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import stevedore
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from nova.openstack.common.gettextutils import _
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from nova.openstack.common import log as logging
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LOG = logging.getLogger(__name__)
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NS = 'nova.hooks'
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_HOOKS = {} # hook name => hook manager
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class HookManager(stevedore.hook.HookManager):
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def __init__(self, name):
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# invoke_on_load creates an instance of the Hook class
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super(HookManager, self).__init__(NS, name, invoke_on_load=True)
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def run_pre(self, name, args, kwargs, f=None):
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for e in self.extensions:
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obj = e.obj
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pre = getattr(obj, 'pre', None)
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if pre:
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LOG.debug(_("Running %(name)s pre-hook: %(obj)s"),
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{'name': name, 'obj': obj})
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if f:
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pre(f, *args, **kwargs)
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else:
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pre(*args, **kwargs)
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def run_post(self, name, rv, args, kwargs, f=None):
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for e in reversed(self.extensions):
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obj = e.obj
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post = getattr(obj, 'post', None)
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if post:
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LOG.debug(_("Running %(name)s post-hook: %(obj)s"),
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{'name': name, 'obj': obj})
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if f:
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post(f, rv, *args, **kwargs)
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else:
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post(rv, *args, **kwargs)
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def add_hook(name, pass_function=False):
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"""Execute optional pre and post methods around the decorated
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function. This is useful for customization around callables.
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"""
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def outer(f):
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@functools.wraps(f)
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def inner(*args, **kwargs):
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manager = _HOOKS.setdefault(name, HookManager(name))
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function = None
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if pass_function:
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function = f
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manager.run_pre(name, args, kwargs, f=function)
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rv = f(*args, **kwargs)
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manager.run_post(name, rv, args, kwargs, f=function)
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return rv
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return inner
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return outer
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def reset():
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"""Clear loaded hooks."""
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_HOOKS.clear()
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