# Service heartbeat driver using Memcached
# Copyright (c) 2013 Akira Yoshiyama <akirayoshiyama at gmail dot com>
#
# This is derived from nova/servicegroup/drivers/db.py.
# Copyright (c) IBM 2012 Pavel Kravchenco <kpavel at il dot ibm dot com>
#                        Alexey Roytman <roytman at il dot ibm dot com>
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
# implied.
# See the License for the specific language governing permissions and
# limitations under the License.

from oslo.config import cfg

from nova import conductor
from nova import context
from nova.openstack.common import log as logging
from nova.openstack.common import memorycache
from nova.openstack.common import timeutils
from nova.servicegroup import api
from nova import utils


CONF = cfg.CONF
CONF.import_opt('service_down_time', 'nova.service')
CONF.import_opt('memcached_servers', 'nova.openstack.common.memorycache')


LOG = logging.getLogger(__name__)


class MemcachedDriver(api.ServiceGroupDriver):

    def __init__(self, *args, **kwargs):
        test = kwargs.get('test')
        if not CONF.memcached_servers and not test:
            raise RuntimeError(_('memcached_servers not defined'))
        self.mc = memorycache.get_client()
        self.db_allowed = kwargs.get('db_allowed', True)
        self.conductor_api = conductor.API(use_local=self.db_allowed)

    def join(self, member_id, group_id, service=None):
        """Join the given service with its group."""

        msg = _('Memcached_Driver: join new ServiceGroup member '
                '%(member_id)s to the %(group_id)s group, '
                'service = %(service)s')
        LOG.debug(msg, locals())
        if service is None:
            raise RuntimeError(_('service is a mandatory argument for '
                                 'Memcached based ServiceGroup driver'))
        report_interval = service.report_interval
        if report_interval:
            pulse = utils.FixedIntervalLoopingCall(self._report_state, service)
            pulse.start(interval=report_interval,
                        initial_delay=report_interval)
            return pulse

    def is_up(self, service_ref):
        """Moved from nova.utils
        Check whether a service is up based on last heartbeat.
        """
        key = "%(topic)s:%(host)s" % service_ref
        return self.mc.get(str(key)) is not None

    def get_all(self, group_id):
        """
        Returns ALL members of the given group
        """
        LOG.debug(_('Memcached_Driver: get_all members of the %s group') %
                  group_id)
        rs = []
        ctxt = context.get_admin_context()
        services = self.conductor_api.service_get_all_by_topic(ctxt, group_id)
        for service in services:
            if self.is_up(service):
                rs.append(service['host'])
        return rs

    def _report_state(self, service):
        """Update the state of this service in the datastore."""
        ctxt = context.get_admin_context()
        try:
            key = "%(topic)s:%(host)s" % service.service_ref
            # memcached has data expiration time capability.
            # set(..., time=CONF.service_down_time) uses it and
            # reduces key-deleting code.
            self.mc.set(str(key),
                        timeutils.utcnow(),
                        time=CONF.service_down_time)

            # TODO(termie): make this pattern be more elegant.
            if getattr(service, 'model_disconnected', False):
                service.model_disconnected = False
                LOG.error(_('Recovered model server connection!'))

        # TODO(vish): this should probably only catch connection errors
        except Exception:  # pylint: disable=W0702
            if not getattr(service, 'model_disconnected', False):
                service.model_disconnected = True
                LOG.exception(_('model server went away'))