71a1e22418
We introduced "shared_targets" and "service_uuid" fields in volumes to allow volume consumers to protect themselves from unintended leftover devices when handling iSCSI connections with shared targets. The way they protect themselves from the automatic scans that happen on detach/map race conditions is by locking and only allowing one attach or one detach operation for each server to happen at a given time. When using an up to date Open iSCSI initiator we don't need to use locks, as it has the possibility to disable automatic LUN scans (which are the real cause of the leftover devices), and OS-Brick already supports this feature. This is currently not the case, since Nova is blindly locking whenever "shared_targets" is set to True. Thanks to the context manager introduced in this patch we can improve our separation of concerns (Nova doesn't have to care when we have to lock), and we can fine tune the locking to only lock when the iSCSI initiator doesn't support disabling automatic scans. The context manager "guard_connection" lives in "os_brick.initiator.utils" and needs a cinder volume. The volume can be passed as a dictionary or OVO instance. Change-Id: I4970363301d5d1f4e7d0f07e09b34d15ee6884c3 Related-Bug: #1800515
47 lines
1.4 KiB
Python
47 lines
1.4 KiB
Python
# Copyright 2018 Red Hat, Inc.
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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 contextlib
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import os
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from oslo_concurrency import lockutils
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from oslo_concurrency import processutils as putils
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def check_manual_scan():
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if os.name == 'nt':
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return False
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try:
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putils.execute('grep', '-F', 'node.session.scan', '/sbin/iscsiadm')
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except putils.ProcessExecutionError:
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return False
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return True
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ISCSI_SUPPORTS_MANUAL_SCAN = check_manual_scan()
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@contextlib.contextmanager
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def guard_connection(device):
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"""Context Manager handling locks for attach/detach operations."""
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if ISCSI_SUPPORTS_MANUAL_SCAN or not device.get('shared_targets'):
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yield
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else:
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# Cinder passes an OVO, but Nova passes a dictionary, so we use dict
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# key access that works with both.
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with lockutils.lock(device['service_uuid'], 'os-brick-'):
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yield
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