96 lines
3.0 KiB
Python
96 lines
3.0 KiB
Python
# vim: tabstop=4 shiftwidth=4 softtabstop=4
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# Copyright 2010 United States Government as represented by the
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# Administrator of the National Aeronautics and Space Administration.
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# Copyright 2011 Justin Santa Barbara
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# Copyright (c) 2012 NTT DOCOMO, INC.
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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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"""Utilities and helper functions."""
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import os
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from oslo.config import cfg
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from tuskar.common import exception
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from tuskar.openstack.common import log as logging
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CONF = cfg.CONF
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LOG = logging.getLogger(__name__)
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class LazyPluggable(object):
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"""A pluggable backend loaded lazily based on some value."""
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def __init__(self, pivot, config_group=None, **backends):
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self.__backends = backends
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self.__pivot = pivot
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self.__backend = None
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self.__config_group = config_group
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def __get_backend(self):
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if not self.__backend:
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if self.__config_group is None:
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backend_name = CONF[self.__pivot]
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else:
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backend_name = CONF[self.__config_group][self.__pivot]
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if backend_name not in self.__backends:
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msg = _('Invalid backend: %s') % backend_name
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raise exception.TuskarException(msg)
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backend = self.__backends[backend_name]
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if isinstance(backend, tuple):
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name = backend[0]
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fromlist = backend[1]
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else:
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name = backend
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fromlist = backend
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self.__backend = __import__(name, None, None, fromlist)
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return self.__backend
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def __getattr__(self, key):
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backend = self.__get_backend()
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return getattr(backend, key)
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def is_int_like(val):
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"""Check if a value looks like an int."""
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try:
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return str(int(val)) == str(val)
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except Exception:
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return False
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def read_cached_file(filename, cache_info, reload_func=None):
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"""Read from a file if it has been modified.
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:param cache_info: dictionary to hold opaque cache.
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:param reload_func: optional function to be called with data when
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file is reloaded due to a modification.
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:returns: data from file
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"""
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mtime = os.path.getmtime(filename)
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if not cache_info or mtime != cache_info.get('mtime'):
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LOG.debug(_("Reloading cached file %s") % filename)
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with open(filename) as fap:
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cache_info['data'] = fap.read()
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cache_info['mtime'] = mtime
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if reload_func:
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reload_func(cache_info['data'])
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return cache_info['data']
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