Add the Hook Point API
Hook points allow installing a package that provide a decorator for some function / method. The intent is to use it for organization specific code. The sample config contains an example. See: https://review.openstack.org/171689/ Implements: blueprint hook-point-api Change-Id: If98d9450cfd6b1a2a3cb23d8bc51940c1b6ee37a
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designate/hookpoints.py
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designate/hookpoints.py
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# Copyright 2015 Rackspace Hosting.
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#
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# Author: Eric Larson <eric.larson@rackspace.com>
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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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import functools
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from oslo_config import cfg
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from oslo_log import log as logging
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from stevedore import hook
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LOG = logging.getLogger(__name__)
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class BaseHook(object):
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OPTS = [
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cfg.BoolOpt('disabled', default=False)
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]
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def __init__(self, group):
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self.group = group
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@property
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def disabled(self):
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return cfg.CONF[self.group].get('disabled', False)
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def wrapper(self, *args, **kw):
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return self.hook_target(*args, **kw)
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def __call__(self, f):
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# Save our hook target as an attribute for our wrapper method
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self.hook_target = f
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@functools.wraps(self.hook_target)
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def wrapper(*args, **kw):
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if self.disabled:
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return self.hook_target(*args, **kw)
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return self.hook(*args, **kw)
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return wrapper
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class hook_point(object):
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NAMESPACE = 'designate.hook_point'
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def __init__(self, name=None):
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self._name = name
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def update_config_opts(self, group, hooks):
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hooks_found = False
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for hook_impl in hooks:
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hooks_found = True
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# Add any options defined by the hook
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if hasattr(hook_impl.plugin, 'OPTS'):
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cfg.CONF.register_opts(hook_impl.plugin.OPTS, group=group)
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if not hooks_found:
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LOG.debug('No hooks found for %s', group)
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else:
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LOG.debug('Created hook: %s', group)
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def hook_manager(self, name):
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LOG.debug('Looking for hooks with: %s %s', self.NAMESPACE, name)
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return hook.HookManager(self.NAMESPACE, name)
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def find_name(self, func=None):
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"""Derive the hook target path from the function name, unless
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a name has been passed in with the constuctor.
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"""
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if self._name:
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return self._name
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if not func:
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return None
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# derive the name from the function
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self._name = '%s.%s' % (func.__module__, func.__name__)
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return self._name
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def init_hook(self, f):
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"""Set up our hook
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Try to inspect the function for a hook target path if one
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wasn't passed in and set up the necessary config options.
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"""
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self.name = self.find_name(f)
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self.group = 'hook_point:%s' % self.name
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self.hooks = self.hook_manager(self.name)
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self.update_config_opts(self.group, self.hooks)
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def enable_hook(self, ext, f):
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"""Enable the hook.
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This instantiates the hook object and decorates the original
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function.
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"""
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decorator = ext.plugin(self.group)
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f = decorator(f)
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f._hook_point = self # add ourselves for inspection
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return f
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def __call__(self, f):
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# Set up all our hook information based on the function or
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# hook point
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self.init_hook(f)
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for h in self.hooks:
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f = self.enable_hook(h, f)
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return f
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@ -229,6 +229,7 @@ class Service(service.RPCService, service.Service):
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'synchronization occurred.'))
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# Standard Create/Update/Delete Methods
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def create_domain(self, context, domain):
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"""
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:param context: Security context information.
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144
designate/tests/test_hookpoints.py
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designate/tests/test_hookpoints.py
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# Copyright 2015 Rackspace Hosting.
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#
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# Author: Eric Larson <eric.larson@rackspace.com>
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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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from mock import Mock
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from mock import patch
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from oslo_config import cfg
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from stevedore.hook import HookManager
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from stevedore.extension import Extension
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from designate.hookpoints import hook_point
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from designate.hookpoints import BaseHook
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from designate.tests import TestCase
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class AddHook(BaseHook):
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OPTS = [
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cfg.Opt('bar'),
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]
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@property
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def bar(self):
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return cfg.CONF[self.group].bar
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def hook(self, *args, **kw):
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return self.hook_target(*args, **kw) + 1
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def get_hook_manager(*hooks):
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hooks = hooks or [AddHook]
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group = 'hook_point:foo'
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ext = [
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Extension('designate_hook', 'foo', hook, hook(group))
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for hook in hooks
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]
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return HookManager.make_test_instance(ext, 'designate_hook')
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def inc(num):
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return num + 1
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class TestHookpoints(TestCase):
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def setUp(self):
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TestCase.setUp(self)
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group = 'hook_point:foo'
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self.CONF.register_group(cfg.OptGroup(group))
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self.CONF.register_opts(BaseHook.OPTS, group=group)
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def test_no_hookpoint_is_noop(self):
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def doit(self, name):
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return 'done: %s' % name
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self.assertEqual(doit, hook_point('foo')(doit))
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def test_hook_is_decorator(self):
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hp = hook_point('foo')
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hp.hook_manager = Mock(return_value=get_hook_manager())
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assert hp(inc)(1) == 3
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def test_apply_N_hooks(self):
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hp = hook_point('foo')
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hp.hook_manager = Mock(return_value=get_hook_manager(AddHook, AddHook))
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assert hp(inc)(1) == 4
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def test_hook_init(self):
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hp = hook_point('foo')
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# Make sure we set up our object when the hook point is
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# applied to a function / method.
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hp.find_name = Mock(return_value='foo.bar.baz')
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hp.hook_manager = Mock(return_value=get_hook_manager())
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hp.find_config = Mock(return_value={'enabled': True})
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hp.update_config_opts = Mock()
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hp(inc)
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self.assertEqual(hp.name, 'foo.bar.baz')
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self.assertEqual(hp.group, 'hook_point:foo.bar.baz')
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hp.update_config_opts.assert_called_with(hp.group, hp.hooks)
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class TestHookpointsConfigOpts(TestCase):
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"""Make sure hooks add the necessary config opts.
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"""
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def test_hook_adds_config_opts(self):
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hp = hook_point('foo')
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hp.hook_manager = Mock(return_value=get_hook_manager())
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hp(inc)
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assert hp.group in self.CONF.keys()
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class TestHookpointsEnabling(TestCase):
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def setUp(self):
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TestCase.setUp(self)
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# NOTE: The options need to be added here via the test classes
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# CONF in order to fall through
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group = 'hook_point:foo'
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self.CONF.register_group(cfg.OptGroup(group))
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self.CONF.register_opts(BaseHook.OPTS, group=group)
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@patch.object(hook_point, 'hook_manager',
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Mock(return_value=get_hook_manager()))
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def test_hook_disabled(self):
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hp = hook_point('foo')
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result_func = hp(inc)
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# We should now have a config option we can set to disabled
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self.config(disabled=True, group='hook_point:foo')
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# The result is 2 so no extra add hook was applied
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self.assertEqual(result_func(1), 2)
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@patch.object(hook_point, 'hook_manager',
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Mock(return_value=get_hook_manager()))
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def test_hook_enabled_when_config_key_exists(self):
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hp = hook_point('foo')
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hp(inc)
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# Add our config
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self.config(bar='from config', group='hook_point:foo')
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# reapply our hook
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result_func = hp(inc)
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# The result is 3 so the extra add hook was applied
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self.assertEqual(result_func(1), 3)
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# Path for Oslo Concurrency to store lock files, defaults to the value
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# of the state_path setting.
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#lock_path = $state_path
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########################
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## Hook Points
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########################
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# Hook Points are enabled when added to the config and there has been
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# a package that provides the corresponding named designate.hook_point
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# entry point.
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# [hook_point:name_of_hook_point]
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# some_param_for_hook = 42
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# Hooks can be disabled in the config
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# enabled = False
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# Hook can also be applied to the import path when the hook has not
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# been given an explicit name. The name is created from the hook
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# target function / method:
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#
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# name = '%s.%s' % (func.__module__, func.__name__)
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# [hook_point:designate.api.v2.controllers.zones.get_one]
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