node.py

import time
import signal
import logging
import logging.config
from threading import Thread
from collections import defaultdict
from functools import partial

import pyev
from sjrpc.core import RpcConnection, RpcError
from sjrpc.utils import ConnectionProxy, RpcHandler, threadless

from ccnode import __version__
from ccnode.config import NodeConfigParser
from ccnode.tags import Tag, get_tags, TagDB
from ccnode.exc import PluginError


logger = logging.getLogger(__name__)


DEFAULT_TAGS = (Tag(u'version', __version__),)


class RPCStartHandler(Thread):
    """Handles rpc connection and authentication to the remote cc-server.

    This class inherits from :class:`Thread` but only the connection part is run
    in a background thread.

    Note:
        As :class:`Thread`, it can be started only one time.

    """
    def __init__(self, loop):
        """
        :param loop: MainLoop instance
        """
        Thread.__init__(self)
        self.daemon = True
        self.run = self.rpc_connect

        self.loop = loop
        # signal to the main thread when connection is done
        self.async = loop.evloop.async(self.async_cb)
        self.timer = loop.evloop.timer(5., 5., self.in_progress_cb)

        self.rpc_con = None
        # id for async rpc call
        self.auth_id = None

    # Method run in the thread
    def rpc_connect(self):
        while True:
            try:
                logger.debug('About to create connection')
                self.rpc_con = RpcConnection.from_addr_ssl(
                    addr=self.loop.config.server_host,
                    port=self.loop.config.server_port,
                    handler=self.loop.rpc_handler,
                    loop=self.loop.evloop,
                    on_disconnect=self.loop.restart_rpc_connection,
                )
                logger.debug('Connection created')
            except IOError:
                logger.exception('Error while connecting to the cc-server')
                time.sleep(5)
            else:
                break

        logger.debug('Async send')
        self.async.send()  # success

    def start(self):
        self.timer.start()
        self.async.start()

        Thread.start(self)

    def stop(self):
        self.timer.stop()
        self.async.stop()

    def in_progress_cb(self, *args):
        logger.info('Connection to the cc-server still in progress')

    def async_cb(self, *args):
        logger.debug('Async callback')
        self.timer.stop()
        # connect is done
        self.loop.rpc_con = self.rpc_con
        # start authentication
        self.timer = self.loop.evloop.timer(.5, 5., self.auth_cb)
        self.timer.start()

    def auth_cb(self, *args):
        logger.debug('Callback auth')
        # check is fallback mode on sjrpc is set otherwise our call would block
        # the loop
        if not self.rpc_con._event_fallback.is_set():
            logger.debug('Will try authentication again latter')
            return

        if self.auth_id is not None:
            logger.error('Authentication is taking longer than expected')
            return

        # try to authenticate
        try:
            self.auth_id = self.rpc_con.rpc.async_call_cb(
                self.auth_done_cb,
                'authentify',
                self.loop.config.server_user,
                self.loop.config.server_passwd,
            )
        except RpcError as exc:
            if exc.exception == 'RpcConnectionError':
                logger.error('Authentication failed: connection lost')
            else:
                logger.exception('Unexpected exception while authenticating')

            self.stop()
            self.loop.restart_rpc_connection()

    def auth_done_cb(self, call_id, response=None, error=None):
        assert call_id == self.auth_id

        if error is not None:
            # we got an error
            logger.error('Error while authenticating with cc-server: %s("%s")',
                         error['exception'], error.get('message', ''))

            # try to reconnect in 5 seconds
            return

        # set handler according to which role was returned by the cc-server
        if response == self.loop.role and response is not None:
            # we don't need to reload the plugins
            # but we need to register the objects and tags
            self.loop.tag_db.rpc_register()
        elif response == u'host':
            # close previous plugins if needed
            if self.loop.role is not None:
                self.loop.close_plugins()
                # re-register the tags of the main loop
                self.loop.tag_db.register()
            logger.debug('Role host affected')
            from ccnode.host import Handler as HostHandler
            self.loop.main_plugin = HostHandler(loop=self.loop)
            self.loop.role = u'host'
            self.loop.register_plugin(self.loop.main_plugin)
        elif response == u'hv':
            # close previous plugins if needed
            if self.loop.role is not None:
                self.loop.close_plugins()
                # re-register the tags of the main loop
                self.loop.tag_db.register()
            logger.debug('Role hypervisor affected')
            # we don't import those modules at the top because some dependancies
            # may not be installed
            from ccnode.hypervisor import Handler as HypervisorHandler
            self.loop.main_plugin = HypervisorHandler(
                hypervisor_name=self.loop.config.server_user,
                loop=self.loop,
            )
            self.loop.role = u'hv'
            self.loop.register_plugin(self.loop.main_plugin)
        else:
            logger.error('Failed authentication, role returned: %s', response)
            self.loop.role = None
            self.auth_id = None
            # we also close the previously opened plugins
            self.loop.close_plugins()
            return  # we retry while it fails

        self.stop()
        logger.info('Successfully authenticated with role %s', str(response))
        self.auth_id = None


class MainLoop(object):
    def __init__(self, config_path):
        self.evloop = pyev.default_loop(debug=True)
        self.config_path = config_path

        # set signal watchers
        self.signals = {
            signal.SIGINT: self.stop,
            signal.SIGTERM: self.stop,
            signal.SIGUSR1: self.reload,
        }

        # turn into real watchers
        self.signals = dict((
            signal,
            self.evloop.signal(signal, cb),
        ) for signal, cb in self.signals.iteritems())

        # load config variables
        self.config = NodeConfigParser(self.config_path)

        # configure logging
        logging.config.fileConfig(self.config_path)

        # rpc connection
        self.rpc_con = None

        self.connect = RPCStartHandler(self)
        self.reconnect = None

        # role
        self.role = None
        self.main_plugin = None

        # tag database
        self.tag_db = TagDB(self, tags=DEFAULT_TAGS)
        # handlers
        self.rpc_handler = dict(
            get_tags=partial(threadless(get_tags), self.tag_db['__main__']),
            sub_tags=self.sub_tags,
        )

        # plugins
        self.registered_plugins = set()

    @property
    def rpc_connected(self):
        return self.rpc_con is not None

    @property
    def rpc_authenticated(self):
        return self.rpc_connected and self.role is not None

    # RPC handlers definitions
    @threadless
    def sub_tags(self, sub_id, tags=None, noresolve_tags=None):
        if sub_id == '__main__':
            # FIXME should we raise ?
            logger.debug('Invalid request for sub object')
            return

        sub_db = self.tag_db.get(sub_id)
        if sub_db is None:
            # FIXME should we also raise here ?
            logger.debug('Failed to find sub_id %s', sub_id)
            return {}

        return get_tags(sub_db, tags, noresolve_tags)
    # End RPC handlers definitions

    def reset_handler(self, name, handl):
        self.rpc_handler[name] = handl

    def remove_handler(self, name):
        self.rpc_handler.pop(name, None)

    def register_plugin(self, plugin):
        # keep track of registered plugins
        if plugin in self.registered_plugins:
            raise PluginError('Plugin was already registered')
        self.registered_plugins.add(plugin)

        # register tags
        self.tag_db.update_from_db(plugin.tag_db)

        # register handler
        self.rpc_handler.update(plugin.rpc_handler)

        plugin.start()

    def unregister_plugin(self, plugin):
        try:
            self.registered_plugins.remove(plugin)
        except KeyError:
            raise PluginError('Plugin was not registered, cannot remove')

        # remove tags
        for db_name, tag_db in plugin.tag_db:
            for tag_name in tag_db:
                del self.tag_db[db_name][tag_name]

            if not self.tag_db[db_name]:  # if there's no more tag in the db
                del self.tag_db[db_name]

        self.tag_db.delete_from_db(plugin.tag_db)

        # remove handlers
        for handler_name in plugin.rpc_handler:
            del self.rpc_handler[handler_name]

        plugin.stop()

    def restart_rpc_connection(self, *args):
        if not self.rpc_connected:
            return

        logger.error('Lost connection to the cc-server, will attempt'
                     ' reconnection')

        # reconnection atempt in one second
        self.reconnect = self.evloop.timer(
            1.,0., self.restart_rpc_connection_cb)
        self.reconnect.start()

    def restart_rpc_connection_cb(self, *args):
        # clear connection
        self.rpc_con = None
        # attempt to connect to the cc-server again
        self.connect = RPCStartHandler(self)
        self.connect.start()
        self.reconnect.stop()
        self.reconnect = None

    def start(self):
        logger.info('Starting node')
        for signal in self.signals.itervalues():
            signal.start()
        logger.debug('About to connect')
        self.connect.start()
        logger.debug('About to start ev_loop')
        self.evloop.start()

    def stop(self, watcher=None, revents=None):
        logger.info('Exiting node...')
        if self.connect is not None:
            self.connect.stop()
        if self.reconnect is not None:
            self.reconnect.stop()
        # close rpc
        if self.rpc_con is not None:
            # disable callback to prevent trampoline calls
            self.rpc_con._on_disconnect = None   # FIXME doesn't work
            self.rpc_con.shutdown()
        # close all plugins
        for plugin in self.registered_plugins:
            plugin.stop()
        self.registered_plugins = set()

        # FIXME check for closing of main tags that were not in plugin
        self.role = None
        self.main_plugin = None
        self.evloop.stop()

    def reload(self, watcher=None, revents=None):
        logger.info(u'Reloading logging configuration...')
        logging.config.fileConfig(self.config_path)