5450f09370
Fixes bug #1213080 and implements blueprint condutor-workers. Make it easy to launch a bunch of conductor processes on a host. Deploying multiple conductor workers per host avoids serialization on database accesses caused by libmysqlclient.so blocking eventlet's single thread. In an experiment on a 24-core machine, when creating 20 VMs in parallel, maximum creation time was reduced by approx. 10s when using 20 conductor processes vis-a-vis a single conductor process. Profiling showed that all of the savings came from faster calls into nova.db.sqlalchemy.api. Note that there are alternative methods for preventing the eventlet thread from blocking during database calls. However, none of these alternatives performed as well as multiple nova-conductor processes. * Instead of using the native database driver like _mysql.so, you can use a pure-python driver, like pymysql by setting sql_connection=mysql+pymysql://... in the [DEFAULT] section of /etc/nova/nova.conf, which eventlet will monkeypatch to avoid blocking. The problem with this approach is the vastly greater CPU demand of the pure-python driver compared to the native driver. Since the pure-python driver is so much more CPU intensive, the eventlet thread spends most of its time talking to the database, which effectively the problem we had before! * Instead of making database calls from eventlet’s thread, you can submit them to eventlet’s pool of worker threads and wait for the results. Try this by setting dbapi_use_tpool=True in the [DEFAULT] section of /etc/nova/nova.conf. The problem I found with this approach was the overhead of synchronizing with the worker threads. In particular, the time elapsed between the worker thread finishing and the waiting coroutine being resumed was typically several times greater than the duration of the database call itself. Change-Id: I8698997d211d7617ee14a1c6113056a694d70620
43 lines
1.3 KiB
Python
43 lines
1.3 KiB
Python
# vim: tabstop=4 shiftwidth=4 softtabstop=4
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# Copyright 2012 IBM Corp.
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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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"""Starter script for Nova Conductor."""
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import sys
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from oslo.config import cfg
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from nova import config
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from nova import objects
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from nova.openstack.common import log as logging
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from nova import service
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from nova import utils
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CONF = cfg.CONF
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CONF.import_opt('topic', 'nova.conductor.api', group='conductor')
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def main():
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objects.register_all()
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config.parse_args(sys.argv)
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logging.setup("nova")
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utils.monkey_patch()
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server = service.Service.create(binary='nova-conductor',
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topic=CONF.conductor.topic,
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manager=CONF.conductor.manager)
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service.serve(server, workers=CONF.conductor.workers)
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service.wait()
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