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OpenStack Study: consistency_db.py

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# Copyright 2014, Big Switch Networks

# 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 sqlalchemy as sa

from neutron.db import api as db

from neutron.db import model_base

from neutron.openstack.common import log as logging

LOG = logging.getLogger(__name__)

A simple table to store the latest consistency hash

received from a server in case neutron gets restarted.

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class ConsistencyHash(model_base.BASEV2):

For now we only support one global state so the

hash_id will always be '1'

__tablename__ = 'consistencyhashes'

hash_id = sa.Column(sa.String(255),

primary_key=True)

hash = sa.Column(sa.String(255), nullable=False)

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def get_consistency_hash(hash_id='1'):

session = db.get_session()

with session.begin(subtransactions=True):

query = session.query(ConsistencyHash)

res = query.filter_by(hash_id=hash_id).first()

return res.hash

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def put_consistency_hash(hash, hash_id='1'):

session = db.get_session()

with session.begin(subtransactions=True):

conhash = ConsistencyHash(hash_id=hash_id, hash=hash)

session.merge(conhash)

LOG.debug(_("Consistency hash for group %(hash_id)s updated "

"to %(hash)s"), {'hash_id': hash_id, 'hash': hash})