OpenStack Study: service_base.py

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# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright 2012 OpenStack Foundation.

# All Rights Reserved.

#

# 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.

import abc

import six

from neutron.api import extensions

from neutron.db import servicetype_db as sdb

from neutron.openstack.common import excutils

from neutron.openstack.common import importutils

from neutron.openstack.common import log as logging

from neutron.services import provider_configuration as pconf

LOG = logging.getLogger(__name__)

@six.add_metaclass(abc.ABCMeta)

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class ServicePluginBase(extensions.PluginInterface):

"""Define base interface for any Advanced Service plugin."""

supported_extension_aliases = []

@abc.abstractmethod

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    def get_plugin_type(self):

        """Return one of predefined service types.

        See neutron/plugins/common/constants.py

        """

        pass

    @abc.abstractmethod

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    def get_plugin_name(self):

        """Return a symbolic name for the plugin.

        Each service plugin should have a symbolic name. This name

        will be used, for instance, by service definitions in service types

        """

        pass

    @abc.abstractmethod

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    def get_plugin_description(self):

        """Return string description of the plugin."""

        pass

def load_drivers(service_type, plugin):

    """Loads drivers for specific service.

    Passes plugin instance to driver's constructor

    """

    service_type_manager = sdb.ServiceTypeManager.get_instance()

    providers = (service_type_manager.

                 get_service_providers(

                     None,

                     filters={'service_type': [service_type]})

                 )

    if not providers:

        msg = (_("No providers specified for '%s' service, exiting") %

               service_type)

        LOG.error(msg)

        raise SystemExit(msg)

    drivers = {}

    for provider in providers:

        try:

            drivers[provider['name']] = importutils.import_object(

                provider['driver'], plugin

            )

            LOG.debug(_("Loaded '%(provider)s' provider for service "

                        "%(service_type)s"),

                      {'provider': provider['driver'],

                       'service_type': service_type})

        except ImportError:

            with excutils.save_and_reraise_exception():

                LOG.exception(_("Error loading provider '%(provider)s' for "

                                "service %(service_type)s"),

                              {'provider': provider['driver'],

                               'service_type': service_type})

    default_provider = None

    try:

        provider = service_type_manager.get_default_service_provider(

            None, service_type)

        default_provider = provider['name']

    except pconf.DefaultServiceProviderNotFound:

        LOG.info(_("Default provider is not specified for service type %s"),

                 service_type)

    return drivers, default_provider

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def load_drivers(service_type, plugin):

    """Loads drivers for specific service.

    Passes plugin instance to driver's constructor

    """

    service_type_manager = sdb.ServiceTypeManager.get_instance()

    providers = (service_type_manager.

                 get_service_providers(

                     None,

                     filters={'service_type': [service_type]})

                 )

    if not providers:

        msg = (_("No providers specified for '%s' service, exiting") %

               service_type)

        LOG.error(msg)

        raise SystemExit(msg)

    drivers = {}

    for provider in providers:

        try:

            drivers[provider['name']] = importutils.import_object(

                provider['driver'], plugin

            )

            LOG.debug(_("Loaded '%(provider)s' provider for service "

                        "%(service_type)s"),

                      {'provider': provider['driver'],

                       'service_type': service_type})

        except ImportError:

            with excutils.save_and_reraise_exception():

                LOG.exception(_("Error loading provider '%(provider)s' for "

                                "service %(service_type)s"),

                              {'provider': provider['driver'],

                               'service_type': service_type})

    default_provider = None

    try:

        provider = service_type_manager.get_default_service_provider(

            None, service_type)

        default_provider = provider['name']

    except pconf.DefaultServiceProviderNotFound:

        LOG.info(_("Default provider is not specified for service type %s"),

                 service_type)

    return drivers, default_provider