89 lines
3.0 KiB
Python
89 lines
3.0 KiB
Python
# Copyright (C) 2021-2022 YADRO.
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# All rights reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import os
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from oslo_log import log as logging
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from cinder.utils import synchronized
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from cinder.volume import volume_utils
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LOG = logging.getLogger(__name__)
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class TatlinVolumeConnections:
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"""Auxiliary class to keep current host volume connections counted
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This class keeps connections of volumes to local host where this
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Cinder instance runs. It prevents disconnection of devices and
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termination of storage links in cases where two Cinder greenthreads
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use the same volume (e.g. creation of new volumes from image cache)
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or connection termination of Nova volume if Nova is collocated on
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the same host (e.g. with snapshots while volumes are attached).
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Once Tatlin implements clones and snaps this class should disappear.
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"""
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def __init__(self, path):
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LOG.debug('Initialize counters for volume connections')
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self.counters = path
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self.create_store()
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@synchronized('tatlin-connections-store', external=True)
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def create_store(self):
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if not os.path.isdir(self.counters):
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os.mkdir(self.counters)
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# We won't intersect with other backend processes
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# because a volume belongs to one backend. Hence
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# no external flag need.
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@synchronized('tatlin-connections-store')
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def increment(self, id):
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counter = os.path.join(self.counters, id)
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connections = 0
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if os.path.exists(counter):
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with open(counter, 'r') as c:
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connections = int(c.read())
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connections += 1
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with open(counter, 'w') as c:
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c.write(str(connections))
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return connections
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@volume_utils.trace
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@synchronized('tatlin-connections-store')
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def decrement(self, id):
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counter = os.path.join(self.counters, id)
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if not os.path.exists(counter):
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return 0
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with open(counter, 'r') as c:
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connections = int(c.read())
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if connections == 1:
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os.remove(counter)
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return 0
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connections -= 1
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with open(counter, 'w') as c:
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c.write(str(connections))
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return connections
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@volume_utils.trace
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@synchronized('tatlin-connections-store')
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def get(self, id):
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counter = os.path.join(self.counters, id)
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if not os.path.exists(counter):
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return 0
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with open(counter, 'r') as c:
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connections = int(c.read())
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return connections
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