kea/src/bin/ddns/ddns.py.in

#!@PYTHON@

# Copyright (C) 2011  Internet Systems Consortium.
#
# Permission to use, copy, modify, and distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notice and this permission notice appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SYSTEMS CONSORTIUM
# DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
# INTERNET SYSTEMS CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT,
# INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
# FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
# NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
# WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.


import sys; sys.path.append ('@@PYTHONPATH@@')
import isc
import bind10_config
from isc.dns import *
from isc.config.ccsession import *
from isc.cc import SessionError, SessionTimeout
import isc.util.process

from isc.log_messages.ddns_messages import *

from optparse import OptionParser, OptionValueError
import os
import signal

isc.log.init("b10-ddns")
logger = isc.log.Logger("ddns")

DATA_PATH = bind10_config.DATA_PATH
if "B10_FROM_BUILD" in os.environ:
    DATA_PATH = os.environ['B10_FROM_BUILD'] + "/src/bin/ddns"
SPECFILE_LOCATION = DATA_PATH + "/ddns.spec"


isc.util.process.rename()

class DDNSConfigError(Exception):
    '''An exception indicating an error in updating ddns configuration.

    This exception is raised when the ddns process encounters an error in
    handling configuration updates.  Not all syntax error can be caught
    at the module-CC layer, so ddns needs to (explicitly or implicitly)
    validate the given configuration data itself.  When it finds an error
    it raises this exception (either directly or by converting an exception
    from other modules) as a unified error in configuration.
    '''
    pass

class DDNSSessionError(Exception):
    '''An exception raised for some unexpected events during a ddns session.
    '''
    pass

class DDNSSession:
    '''Class to handle one DDNS update'''

    def __init__(self):
        '''Initialize a DDNS Session'''
        pass

class DDNSServer:
    def __init__(self, cc_session=None):
        '''
        Initialize the DDNS Server.
        This sets up a ModuleCCSession for the BIND 10 system.
        Parameters:
        cc_session: If None (default), a new ModuleCCSession will be set up.
                    If specified, the given session will be used. This is
                    mainly used for testing.
        '''
        if cc_session is not None:
            self._cc = cc_session
        else:
            self._cc = isc.config.ModuleCCSession(SPECFILE_LOCATION,
                                                  self.config_handler,
                                                  self.command_handler)

        self._config_data = self._cc.get_full_config()
        self._cc.start()
        self._shutdown = False

    def config_handler(self, new_config):
        '''Update config data.'''
        answer = create_answer(0)
        return answer

    def command_handler(self, cmd, args):
        '''
        Handle a CC session command, as sent from bindctl or other
        BIND 10 modules.
        '''
        if cmd == "shutdown":
            logger.info(DDNS_RECEIVED_SHUTDOWN_COMMAND)
            self.shutdown()
            answer = create_answer(0)
        else:
            answer = create_answer(1, "Unknown command: " + str(cmd))
        return answer

    def shutdown(self):
        '''
        Shut down the server. Perform any cleanup that is necessary.
        Currently, this only sets the internal _shutdown value to true,
        so the main loop in run() stops.
        '''
        self._shutdown = True
        logger.info(DDNS_SHUTDOWN)

    def run(self):
        '''
        Get and process all commands sent from cfgmgr or other modules.
        This loops waiting for events until self.shutdown() has been called.
        '''
        logger.info(DDNS_RUNNING)
        while not self._shutdown:
            # We do not catch any exceptions here right now, but this would
            # be a good place to catch any exceptions that b10-ddns can
            # recover from. We currently have no exception hierarchy to
            # make such a distinction easily, but once we do, this would
            # be the place to catch.
            self._cc.check_command(False)
        logger.info(DDNS_STOPPED)

def create_signal_handler(ddns_server):
    '''
    This creates a signal_handler for use in set_signal_handler, which
    shuts down the given DDNSServer (or any object that has a shutdown()
    method)
    '''
    def signal_handler(signal, frame):
        '''
        Handler for process signals. Since only signals to shut down are sent
        here, the actual signal is not checked and the server is simply shut
        down.
        '''
        ddns_server.shutdown()
    return signal_handler

def set_signal_handler(signal_handler):
    '''
    Sets the signal handler(s).
    '''
    signal.signal(signal.SIGTERM, signal_handler)
    signal.signal(signal.SIGINT, signal_handler)

def set_cmd_options(parser):
    '''
    Helper function to set command-line options
    '''
    parser.add_option("-v", "--verbose", dest="verbose", action="store_true",
            help="display more about what is going on")

def main(ddns_server=None):
    '''
    The main function.
    Parameters:
    ddns_server: If None (default), a DDNSServer object is initialized.
                 If specified, the given DDNSServer will be used. This is
                 mainly used for testing.
    cc_session: If None (default), a new ModuleCCSession will be set up.
                If specified, the given session will be used. This is
                mainly used for testing.
    '''
    try:
        parser = OptionParser()
        set_cmd_options(parser)
        (options, args) = parser.parse_args()
        if options.verbose:
            print("[b10-ddns] Warning: -v verbose option is ignored at this point.")

        if ddns_server is None:
            ddns_server = DDNSServer()
        set_signal_handler(create_signal_handler(ddns_server))
        ddns_server.run()
    except KeyboardInterrupt:
        logger.info(DDNS_STOPPED_BY_KEYBOARD)
    except SessionError as e:
        logger.error(DDNS_CC_SESSION_ERROR, str(e))
    except ModuleCCSessionError as e:
        logger.error(DDNS_MODULECC_SESSION_ERROR, str(e))
    except DDNSConfigError as e:
        logger.error(DDNS_CONFIG_ERROR, str(e))
    except SessionTimeout as e:
        logger.error(DDNS_CC_SESSION_TIMEOUT_ERROR)
    except Exception as e:
        logger.error(DDNS_UNCAUGHT_EXCEPTION, type(e).__name__, str(e))

if '__main__' == __name__:
    main()