/mysql_watcher/indra/base/config.py

"""\
@file config.py
@brief Utility module for parsing and accessing the indra.xml config file.

$LicenseInfo:firstyear=2006&license=mit$

Copyright (c) 2006-2009, Linden Research, Inc.

Permission is hereby granted, free of charge, to any person obtaining a copy
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The above copyright notice and this permission notice shall be included in
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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"""

import copy
import errno
import os
import traceback
import time
import types

from os.path import dirname, getmtime, join, realpath
from indra.base import llsd

_g_config = None

class IndraConfig(object):
    """
    IndraConfig loads a 'indra' xml configuration file
    and loads into memory.  This representation in memory
    can get updated to overwrite values or add new values.

    The xml configuration file is considered a live file and changes
    to the file are checked and reloaded periodically.  If a value had
    been overwritten via the update or set method, the loaded values
    from the file are ignored (the values from the update/set methods
    override)
    """
    def __init__(self, indra_config_file):
        self._indra_config_file = indra_config_file
        self._reload_check_interval = 30 # seconds
        self._last_check_time = 0
        self._last_mod_time = 0

        self._config_overrides = {}
        self._config_file_dict = {}
        self._combined_dict = {}

        self._load()

    def _load(self):
        # if you initialize the IndraConfig with None, no attempt
        # is made to load any files
        if self._indra_config_file is None:
            return

        config_file = open(self._indra_config_file)
        self._config_file_dict = llsd.parse(config_file.read())
        self._combine_dictionaries()
        config_file.close()

        self._last_mod_time = self._get_last_modified_time()
        self._last_check_time = time.time() # now

    def _get_last_modified_time(self):
        """
        Returns the mtime (last modified time) of the config file,
        if such exists.
        """
        if self._indra_config_file is not None:
            return os.path.getmtime(self._indra_config_file)

        return 0

    def _combine_dictionaries(self):
        self._combined_dict = {}
        self._combined_dict.update(self._config_file_dict)
        self._combined_dict.update(self._config_overrides)

    def _reload_if_necessary(self):
        now = time.time()

        if (now - self._last_check_time) > self._reload_check_interval:
            self._last_check_time = now
            try:
                modtime = self._get_last_modified_time()
                if modtime > self._last_mod_time:
                    self._load()
            except OSError, e:
                if e.errno == errno.ENOENT: # file not found
                    # someone messed with our internal state
                    # or removed the file

                    print 'WARNING: Configuration file has been removed ' + (self._indra_config_file)
                    print 'Disabling reloading of configuration file.'

                    traceback.print_exc()

                    self._indra_config_file = None
                    self._last_check_time = 0
                    self._last_mod_time = 0
                else:
                    raise  # pass the exception along to the caller

    def __getitem__(self, key):
        self._reload_if_necessary()

        return self._combined_dict[key]

    def get(self, key, default = None):
        try:
            return self.__getitem__(key)
        except KeyError:
            return default

    def __setitem__(self, key, value):
        """
        Sets the value of the config setting of key to be newval

        Once any key/value pair is changed via the set method,
        that key/value pair will remain set with that value until
        change via the update or set method
        """
        self._config_overrides[key] = value
        self._combine_dictionaries()

    def set(self, key, newval):
        return self.__setitem__(key, newval)

    def update(self, new_conf):
        """
        Load an XML file and apply its map as overrides or additions
        to the existing config.  Update can be a file or a dict.

        Once any key/value pair is changed via the update method,
        that key/value pair will remain set with that value until
        change via the update or set method
        """
        if isinstance(new_conf, dict):
            overrides = new_conf
        else:
            # assuming that it is a filename
            config_file = open(new_conf)
            overrides = llsd.parse(config_file.read())
            config_file.close()
  
        self._config_overrides.update(overrides)
        self._combine_dictionaries()

    def as_dict(self):
        """
        Returns immutable copy of the IndraConfig as a dictionary
        """
        return copy.deepcopy(self._combined_dict)

def load(config_xml_file = None):
    global _g_config

    load_default_files = config_xml_file is None
    if load_default_files:
        ## going from:
        ## "/opt/linden/indra/lib/python/indra/base/config.py"
        ## to:
        ## "/opt/linden/etc/indra.xml"
        config_xml_file = realpath(
            dirname(realpath(__file__)) + "../../../../../../etc/indra.xml")

    try:
        _g_config = IndraConfig(config_xml_file)
    except IOError:
        # Failure to load passed in file
        # or indra.xml default file
        if load_default_files:
            try:
                config_xml_file = realpath(
                    dirname(realpath(__file__)) + "../../../../../../etc/globals.xml")
                _g_config = IndraConfig(config_xml_file)
                return
            except IOError:
                # Failure to load globals.xml
                # fall to code below
                pass

        # Either failed to load passed in file
        # or failed to load all default files
        _g_config = IndraConfig(None)

def dump(indra_xml_file, indra_cfg = None, update_in_mem=False):
    '''
    Dump config contents into a file
    Kindof reverse of load.
    Optionally takes a new config to dump.
    Does NOT update global config unless requested.
    '''
    global _g_config

    if not indra_cfg:
        if _g_config is None:
            return

        indra_cfg = _g_config.as_dict()

    if not indra_cfg:
        return

    config_file = open(indra_xml_file, 'w')
    _config_xml = llsd.format_xml(indra_cfg)
    config_file.write(_config_xml)
    config_file.close()

    if update_in_mem:
        update(indra_cfg)

def update(new_conf):
    global _g_config

    if _g_config is None:
        # To keep with how this function behaved
        # previously, a call to update
        # before the global is defined
        # make a new global config which does not
        # load data from a file.
        _g_config = IndraConfig(None)

    return _g_config.update(new_conf)

def get(key, default = None):
    global _g_config

    if _g_config is None:
        load()

    return _g_config.get(key, default)

def set(key, newval):
    """
    Sets the value of the config setting of key to be newval

    Once any key/value pair is changed via the set method,
    that key/value pair will remain set with that value until
    change via the update or set method or program termination
    """
    global _g_config

    if _g_config is None:
        _g_config = IndraConfig(None)

    _g_config.set(key, newval)

def get_config():
    global _g_config
    return _g_config