888bf204e6
This sketches in generic code for handling YAML configuration. It includes a code-based validation that is used for generating helpful configuration error messages. Related to RM7484. TODO: * Add functional tests for configuration system
100 lines
3.0 KiB
Python
100 lines
3.0 KiB
Python
# Copyright 2014 Rackspace
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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");
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# you may not use this file except in compliance with the
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# License. You may obtain 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,
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# software distributed under the License is distributed on an "AS
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# IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
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# express or implied. See the License for the specific language
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# governing permissions and limitations under the License.
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import os
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import time
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import six
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def canonicalize_path(cwd, path):
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"""
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Canonicalizes a path relative to a given working directory.
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:param cwd: The working directory to interpret ``path`` relative
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to.
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:param path: The path to canonicalize. If relative, it will be
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interpreted relative to ``cwd``.
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:returns: The absolute path.
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"""
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if not os.path.isabs(path):
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path = os.path.join(cwd, path)
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return os.path.abspath(path)
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def backoff(max_tries):
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"""
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A generator to perform simplified exponential backoff. Yields up
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to the specified number of times, performing a ``time.sleep()``
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with an exponentially increasing sleep time (starting at 1 second)
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between each trial. Yields the (0-based) trial number.
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:param max_tries: The maximum number of tries to attempt.
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"""
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# How much time will we sleep next time?
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sleep = 1
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for i in range(max_tries):
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# Yield the trial number
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yield i
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# We've re-entered the loop; sleep, then increment the sleep
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# time
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time.sleep(sleep)
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sleep <<= 1
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def boolean(value, default=None):
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"""
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Convert a string value into a boolean. The values 'true', 't',
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'yes', 'y', and 'on', as well as non-zero integer values, are
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recognized as ``True``, while the values 'false', 'f', 'no', 'n',
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and 'off', as well as the integer value 0, are recognized as
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``False``. A ``ValueError`` is raised for other values unless the
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``default`` parameter is given, in which case it is returned.
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:param value: The string value to be converted to boolean.
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:param default: If not ``None``, specifies the desired default
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value if the ``value`` is not one of the
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recognized values.
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:returns: The boolean value derived from the string.
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"""
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# Cover non-string case
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if not isinstance(value, six.string_types):
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return bool(value)
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# Cover the integer case
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if value.isdigit():
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return bool(int(value))
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# Check for recognized values
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tmp = value.lower()
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if tmp in ('true', 't', 'yes', 'y', 'on'):
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return True
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elif tmp in ('false', 'f', 'no', 'n', 'off'):
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return False
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# Return the default value
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if default is not None:
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return default
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raise ValueError('invalid boolean literal %r' % value)
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