/mysql_watcher/indra/base/config.py

  1"""\
  2@file config.py
  3@brief Utility module for parsing and accessing the indra.xml config file.
  4
  5$LicenseInfo:firstyear=2006&license=mit$
  6
  7Copyright (c) 2006-2009, Linden Research, Inc.
  8
  9Permission is hereby granted, free of charge, to any person obtaining a copy
 10of this software and associated documentation files (the "Software"), to deal
 11in the Software without restriction, including without limitation the rights
 12to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 13copies of the Software, and to permit persons to whom the Software is
 14furnished to do so, subject to the following conditions:
 15
 16The above copyright notice and this permission notice shall be included in
 17all copies or substantial portions of the Software.
 18
 19THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 20IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 21FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 22AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 23LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 24OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 25THE SOFTWARE.
 26$/LicenseInfo$
 27"""
 28
 29import copy
 30import errno
 31import os
 32import traceback
 33import time
 34import types
 35
 36from os.path import dirname, getmtime, join, realpath
 37from indra.base import llsd
 38
 39_g_config = None
 40
 41class IndraConfig(object):
 42    """
 43    IndraConfig loads a 'indra' xml configuration file
 44    and loads into memory.  This representation in memory
 45    can get updated to overwrite values or add new values.
 46
 47    The xml configuration file is considered a live file and changes
 48    to the file are checked and reloaded periodically.  If a value had
 49    been overwritten via the update or set method, the loaded values
 50    from the file are ignored (the values from the update/set methods
 51    override)
 52    """
 53    def __init__(self, indra_config_file):
 54        self._indra_config_file = indra_config_file
 55        self._reload_check_interval = 30 # seconds
 56        self._last_check_time = 0
 57        self._last_mod_time = 0
 58
 59        self._config_overrides = {}
 60        self._config_file_dict = {}
 61        self._combined_dict = {}
 62
 63        self._load()
 64
 65    def _load(self):
 66        # if you initialize the IndraConfig with None, no attempt
 67        # is made to load any files
 68        if self._indra_config_file is None:
 69            return
 70
 71        config_file = open(self._indra_config_file)
 72        self._config_file_dict = llsd.parse(config_file.read())
 73        self._combine_dictionaries()
 74        config_file.close()
 75
 76        self._last_mod_time = self._get_last_modified_time()
 77        self._last_check_time = time.time() # now
 78
 79    def _get_last_modified_time(self):
 80        """
 81        Returns the mtime (last modified time) of the config file,
 82        if such exists.
 83        """
 84        if self._indra_config_file is not None:
 85            return os.path.getmtime(self._indra_config_file)
 86
 87        return 0
 88
 89    def _combine_dictionaries(self):
 90        self._combined_dict = {}
 91        self._combined_dict.update(self._config_file_dict)
 92        self._combined_dict.update(self._config_overrides)
 93
 94    def _reload_if_necessary(self):
 95        now = time.time()
 96
 97        if (now - self._last_check_time) > self._reload_check_interval:
 98            self._last_check_time = now
 99            try:
100                modtime = self._get_last_modified_time()
101                if modtime > self._last_mod_time:
102                    self._load()
103            except OSError, e:
104                if e.errno == errno.ENOENT: # file not found
105                    # someone messed with our internal state
106                    # or removed the file
107
108                    print 'WARNING: Configuration file has been removed ' + (self._indra_config_file)
109                    print 'Disabling reloading of configuration file.'
110
111                    traceback.print_exc()
112
113                    self._indra_config_file = None
114                    self._last_check_time = 0
115                    self._last_mod_time = 0
116                else:
117                    raise  # pass the exception along to the caller
118
119    def __getitem__(self, key):
120        self._reload_if_necessary()
121
122        return self._combined_dict[key]
123
124    def get(self, key, default = None):
125        try:
126            return self.__getitem__(key)
127        except KeyError:
128            return default
129
130    def __setitem__(self, key, value):
131        """
132        Sets the value of the config setting of key to be newval
133
134        Once any key/value pair is changed via the set method,
135        that key/value pair will remain set with that value until
136        change via the update or set method
137        """
138        self._config_overrides[key] = value
139        self._combine_dictionaries()
140
141    def set(self, key, newval):
142        return self.__setitem__(key, newval)
143
144    def update(self, new_conf):
145        """
146        Load an XML file and apply its map as overrides or additions
147        to the existing config.  Update can be a file or a dict.
148
149        Once any key/value pair is changed via the update method,
150        that key/value pair will remain set with that value until
151        change via the update or set method
152        """
153        if isinstance(new_conf, dict):
154            overrides = new_conf
155        else:
156            # assuming that it is a filename
157            config_file = open(new_conf)
158            overrides = llsd.parse(config_file.read())
159            config_file.close()
160  
161        self._config_overrides.update(overrides)
162        self._combine_dictionaries()
163
164    def as_dict(self):
165        """
166        Returns immutable copy of the IndraConfig as a dictionary
167        """
168        return copy.deepcopy(self._combined_dict)
169
170def load(config_xml_file = None):
171    global _g_config
172
173    load_default_files = config_xml_file is None
174    if load_default_files:
175        ## going from:
176        ## "/opt/linden/indra/lib/python/indra/base/config.py"
177        ## to:
178        ## "/opt/linden/etc/indra.xml"
179        config_xml_file = realpath(
180            dirname(realpath(__file__)) + "../../../../../../etc/indra.xml")
181
182    try:
183        _g_config = IndraConfig(config_xml_file)
184    except IOError:
185        # Failure to load passed in file
186        # or indra.xml default file
187        if load_default_files:
188            try:
189                config_xml_file = realpath(
190                    dirname(realpath(__file__)) + "../../../../../../etc/globals.xml")
191                _g_config = IndraConfig(config_xml_file)
192                return
193            except IOError:
194                # Failure to load globals.xml
195                # fall to code below
196                pass
197
198        # Either failed to load passed in file
199        # or failed to load all default files
200        _g_config = IndraConfig(None)
201
202def dump(indra_xml_file, indra_cfg = None, update_in_mem=False):
203    '''
204    Dump config contents into a file
205    Kindof reverse of load.
206    Optionally takes a new config to dump.
207    Does NOT update global config unless requested.
208    '''
209    global _g_config
210
211    if not indra_cfg:
212        if _g_config is None:
213            return
214
215        indra_cfg = _g_config.as_dict()
216
217    if not indra_cfg:
218        return
219
220    config_file = open(indra_xml_file, 'w')
221    _config_xml = llsd.format_xml(indra_cfg)
222    config_file.write(_config_xml)
223    config_file.close()
224
225    if update_in_mem:
226        update(indra_cfg)
227
228def update(new_conf):
229    global _g_config
230
231    if _g_config is None:
232        # To keep with how this function behaved
233        # previously, a call to update
234        # before the global is defined
235        # make a new global config which does not
236        # load data from a file.
237        _g_config = IndraConfig(None)
238
239    return _g_config.update(new_conf)
240
241def get(key, default = None):
242    global _g_config
243
244    if _g_config is None:
245        load()
246
247    return _g_config.get(key, default)
248
249def set(key, newval):
250    """
251    Sets the value of the config setting of key to be newval
252
253    Once any key/value pair is changed via the set method,
254    that key/value pair will remain set with that value until
255    change via the update or set method or program termination
256    """
257    global _g_config
258
259    if _g_config is None:
260        _g_config = IndraConfig(None)
261
262    _g_config.set(key, newval)
263
264def get_config():
265    global _g_config
266    return _g_config