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annotate src/memory/cache.py @ 2162:c9a67eb5bf72

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jp (base): improved module import: module import now display a warning were suitable on import issue
author Goffi <goffi@goffi.org>
date Tue, 21 Feb 2017 21:01:40 +0100
parents 766dbbec56f2
children 1b3fbb76984b
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rev   line source
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1 #!/usr/bin/env python2
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2 # -*- coding: utf-8 -*-
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3
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4 # SAT: a jabber client
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5 # Copyright (C) 2009-2016 Jérôme Poisson (goffi@goffi.org)
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6
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7 # This program is free software: you can redistribute it and/or modify
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8 # it under the terms of the GNU Affero General Public License as published by
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9 # the Free Software Foundation, either version 3 of the License, or
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10 # (at your option) any later version.
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11
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12 # This program is distributed in the hope that it will be useful,
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13 # but WITHOUT ANY WARRANTY; without even the implied warranty of
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14 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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15 # GNU Affero General Public License for more details.
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16
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17 # You should have received a copy of the GNU Affero General Public License
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18 # along with this program. If not, see <http://www.gnu.org/licenses/>.
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19
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20 from sat.core.log import getLogger
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21 log = getLogger(__name__)
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22 from sat.core import exceptions
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23 from sat.core.constants import Const as C
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24 import cPickle as pickle
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25 import mimetypes
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26 import os.path
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27 import time
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28
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29
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30 class Cache(object):
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31 """generic file caching"""
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32
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33 def __init__(self, host, profile=None):
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34 host = host
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35 self.profile = profile
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36 self.cache_dir = os.path.join(
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37 host.memory.getConfig('', 'local_dir'),
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38 C.CACHE_DIR,
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39 profile or '')
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40 if not os.path.exists(self.cache_dir):
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41 os.makedirs(self.cache_dir)
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42
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43 def getPath(self, filename):
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44 """return cached file URL
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45
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46 @param filename(unicode): cached file name (cache data or actual file)
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47 """
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48 if not filename or u'/' in filename:
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49 log.error(u"invalid char found in file name, hack attempt? name:{}".format(filename))
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50 raise exceptions.DataError(u"Invalid char found")
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51 return os.path.join(self.cache_dir, filename)
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52
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53 def getFilePath(self, uid):
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54 """retrieve absolute path to file
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55
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56 @param uid(unicode): unique identifier of file
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57 @return (unicode, None): absolute path to cached file
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58 None if file is not in cache (or cache is invalid)
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59 """
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60 uid = uid.strip()
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61 if not uid:
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62 return None
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63 cache_url = self.getPath(uid)
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64 if not os.path.exists(cache_url):
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65 return None
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66
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67 try:
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68 with open(cache_url, 'rb') as f:
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69 cache_data = pickle.load(f)
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70 except IOError:
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71 log.warning(u"can't read cache at {}".format(cache_url))
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72 return None
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73
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74 except pickle.UnpicklingError:
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75 log.warning(u'invalid cache found at {}'.format(cache_url))
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76 return None
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77
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78 try:
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79 eol = cache_data['eol']
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80 except KeyError:
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81 log.warning(u'no End Of Life found for cached file {}'.format(uid))
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82 eol = 0
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83 if eol < time.time():
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84 log.debug(u"removing expired cache (expired for {}s)".format(
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85 time.time() - eol))
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86 return None
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87
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88 return self.getPath(cache_data['filename'])
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89
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90 def cacheData(self, source, uid, mime_type=u'', max_age=None, filename=None):
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91 """create cache metadata and file object to use for actual data
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92
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93 @param source(unicode): source of the cache (should be plugin's import_name)
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94 @param uid(unicode): an identifier of the file which must be unique
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95 @param mime_type(unicode): MIME type of the file to cache
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96 it will be used notably to guess file extension
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97 @param max_age(int, None): maximum age in seconds
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98 the cache metadata will have an "eol" (end of life)
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99 None to use default value
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100 0 to ignore cache (file will be re-downloaded on each access)
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101 @param filename: if not None, will be used as filename
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102 else one will be generated from uid and guessed extension
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103 @return(file): file object opened in write mode
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104 you have to close it yourself (hint: use with statement)
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105 """
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106 # FIXME: is it needed to use a separate thread?
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107 # probably not with the little data expected with BoB
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108 cache_url = self.getPath(uid)
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109 ext = mimetypes.guess_extension(mime_type, strict=False)
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110 if ext is None:
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111 log.warning(u"can't find extension for MIME type {}".format(mime_type))
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112 ext = '.dump'
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113 if filename is None:
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114 filename = uid + ext
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115 if max_age is None:
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116 max_age = C.DEFAULT_MAX_AGE
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117 cache_data = {'source': source,
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118 'filename': filename,
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119 'eol': int(time.time()) + max_age,
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120 'mime_type': mime_type,
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121 }
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122 file_path = self.getPath(filename)
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123
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124 with open(cache_url, 'wb') as f:
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125 pickle.dump(cache_data, f, protocol=2)
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126
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127 return open(file_path, 'wb')