9d9fc01dd3
This change adds the ability to monitor the local ovsdb for interface changes so that the l2 agent can avoid unnecessary polling. Minimal changes are made to the agent so the risk of breakage should be low. Future efforts to make the agent entirely event-based may be able to use OvsdbMonitor as a starting point. By default polling minimization is not done, and can only be enabled by setting 'minimize_polling = True' in the ovs section of the l2 agent's config file. Closes-Bug: #1177973 Change-Id: I26c035b48a74df2148696869c5a9affae5ab3d27
115 lines
4.0 KiB
Python
115 lines
4.0 KiB
Python
# vim: tabstop=4 shiftwidth=4 softtabstop=4
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# Copyright 2013 Red Hat, Inc.
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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 eventlet
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from neutron.agent.linux import async_process
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from neutron.openstack.common import log as logging
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LOG = logging.getLogger(__name__)
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class OvsdbMonitor(async_process.AsyncProcess):
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"""Manages an invocation of 'ovsdb-client monitor'."""
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def __init__(self, table_name, columns=None, format=None,
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root_helper=None, respawn_interval=None):
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cmd = ['ovsdb-client', 'monitor', table_name]
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if columns:
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cmd.append(','.join(columns))
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if format:
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cmd.append('--format=%s' % format)
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super(OvsdbMonitor, self).__init__(cmd,
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root_helper=root_helper,
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respawn_interval=respawn_interval)
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def _read_stdout(self):
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data = self._process.stdout.readline()
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if not data:
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return
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#TODO(marun) The default root helper outputs exit errors to
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# stdout due to bug #1219530. This check can be moved to
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# _read_stderr once the error is correctly output to stderr.
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if self.root_helper and self.root_helper in data:
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self._stderr_lines.put(data)
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LOG.error(_('Error received from ovsdb monitor: %s') % data)
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else:
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self._stdout_lines.put(data)
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LOG.debug(_('Output received from ovsdb monitor: %s') % data)
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return data
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def _read_stderr(self):
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data = super(OvsdbMonitor, self)._read_stderr()
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if data:
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LOG.error(_('Error received from ovsdb monitor: %s') % data)
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# Do not return value to ensure that stderr output will
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# stop the monitor.
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class SimpleInterfaceMonitor(OvsdbMonitor):
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"""Monitors the Interface table of the local host's ovsdb for changes.
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The has_updates() method indicates whether changes to the ovsdb
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Interface table have been detected since the monitor started or
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since the previous access.
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"""
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def __init__(self, root_helper=None, respawn_interval=None):
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super(SimpleInterfaceMonitor, self).__init__(
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'Interface',
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columns=['name'],
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format='json',
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root_helper=root_helper,
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respawn_interval=respawn_interval,
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)
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self.data_received = False
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@property
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def is_active(self):
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return (self.data_received and
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self._kill_event and
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not self._kill_event.ready())
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@property
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def has_updates(self):
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"""Indicate whether the ovsdb Interface table has been updated.
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True will be returned if the monitor process is not active.
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This 'failing open' minimizes the risk of falsely indicating
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the absense of updates at the expense of potential false
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positives.
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"""
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return bool(list(self.iter_stdout())) or not self.is_active
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def start(self, block=False, timeout=5):
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super(SimpleInterfaceMonitor, self).start()
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if block:
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eventlet.timeout.Timeout(timeout)
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while not self.is_active:
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eventlet.sleep()
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def _kill(self, *args, **kwargs):
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self.data_received = False
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super(SimpleInterfaceMonitor, self)._kill(*args, **kwargs)
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def _read_stdout(self):
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data = super(SimpleInterfaceMonitor, self)._read_stdout()
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if data and not self.data_received:
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self.data_received = True
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return data
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