95 lines
3.2 KiB
Python
95 lines
3.2 KiB
Python
# 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 copy
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import distutils.version
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import logging
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import threading
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import six
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import stevedore
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LOG = logging.getLogger(__name__)
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def reraise_endpoint_load_failure(manager, endpoint, exc):
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LOG.error('Failed to load %s: %s', endpoint.name, exc)
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raise # Avoid unexpectedly skipped steps
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class Manager(object):
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default_config = None
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name = None
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def __init__(self):
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self.config = self.get_config(self.name)
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self.transformers = self.load_transformers(self.name, self.config)
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@classmethod
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def get_config(cls, name):
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# TODO(yorik-sar): merge actual config with defaults
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return cls.default_config
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@staticmethod
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def load_transformers(name, config):
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transformers = []
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for version, names in six.iteritems(config):
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extension_manager = stevedore.ExtensionManager(
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'nailgun.cluster_upgrade.transformations.{}.{}'.format(
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name, version),
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on_load_failure_callback=reraise_endpoint_load_failure,
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)
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try:
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sorted_extensions = [extension_manager[n].plugin
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for n in names]
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except KeyError as exc:
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LOG.error('%s transformer %s not found for version %s',
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name, exc, version)
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raise
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strict_version = distutils.version.StrictVersion(version)
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transformers.append((strict_version, sorted_extensions))
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transformers.sort()
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return transformers
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def apply(self, from_version, to_version, data):
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strict_from = distutils.version.StrictVersion(from_version)
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strict_to = distutils.version.StrictVersion(to_version)
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assert strict_from <= strict_to, \
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"from_version must not be greater than to_version"
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data = copy.deepcopy(data)
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for version, transformers in self.transformers:
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if version <= strict_from:
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continue
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if version > strict_to:
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break
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for transformer in transformers:
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LOG.debug("Applying %s transformer %s",
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self.name, transformer)
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data = transformer(data)
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return data
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class Lazy(object):
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def __init__(self, mgr_cls):
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self.mgr_cls = mgr_cls
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self.mgr = None
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self.lock = threading.Lock()
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def apply(self, *args, **kwargs):
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if self.mgr is None:
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with self.lock:
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if self.mgr is None:
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self.mgr = self.mgr_cls()
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self.apply = self.mgr.apply
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return self.mgr.apply(*args, **kwargs)
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