79 lines
2.6 KiB
Python
79 lines
2.6 KiB
Python
# -*- coding: utf-8 -*- #
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# Copyright 2017 Google LLC. 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 License.
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# 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, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Common utilities for using the persistent cache."""
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from __future__ import absolute_import
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from __future__ import division
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from __future__ import unicode_literals
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import functools
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from googlecloudsdk.core import resources
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from googlecloudsdk.core.cache import exceptions as cache_exceptions
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def CacheResource(table_prefix, timeout_sec=604800):
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"""Decorator to cache the result of a function.
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The decorated function must return a resource.
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The returned function will take three arguments:
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cache: a Cache object.
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key: str, the key for the function call in the cache.
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args: tuple (optional), the arguments to pass to the original function. If
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not specified, key will be used.
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>>> @CacheResource('sums')
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... def Add(value1, value2):
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... print 'adding...'
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... value = value1 + value2
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... return resources.REGISTRY.Parse(str(value), collection='...')
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>>> with cache_util.GetCache('resource://') as cache:
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... print Add(cache, '1+4', (1, 4))
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... print Add(cache, '1+4', (1, 4))
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adding...
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http://example.googleapis.com/v1/foos/5
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http://example.googleapis.com/v1/foos/5
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Args:
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table_prefix: str, a prefix for the names of the tables in the cache to use
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for these results
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timeout_sec: int, the time (in seconds) for which a table is valid
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Returns:
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function, a function that decorates with the appropriate behavior.
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"""
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def Wrapper(func):
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"""Wraps a function and caches its result."""
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@functools.wraps(func)
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def GetFromCache(cache, key, args=None):
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table_name = '{}:{}'.format(table_prefix, key)
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table = cache.Table(table_name, columns=1, timeout=timeout_sec)
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try:
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result = table.Select()
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except cache_exceptions.CacheTableExpired:
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args = args if args is not None else (key,)
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ref = func(*args)
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table.AddRows([(ref.SelfLink(),)])
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table.Validate()
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return ref
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else:
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url = result[0][0]
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return resources.REGISTRY.ParseURL(url)
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return GetFromCache
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return Wrapper
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