Trace Source Code: nova scheduler (OpenStack Kilo)

Code tracing in Nova Scheduler (Kilo)

Nova Scheduler in Kilo

We started from nova/nova/scheduler/manage.py and its function select_destinations,
that is the beginning of the nova-schduler.
Here is the an example for quick understanding the RabbitMQ Server Side that compared the section of reference for oslo.messaging in this Blog.

And the Client side is from nova-conductor.

And the nova/nova/scheduler/manage.py is here.

class SchedulerManager(manager.Manager):
    """Chooses a host to run instances on."""

    target = messaging.Target(version='4.2')

    def __init__(self, scheduler_driver=None, *args, **kwargs):
        if not scheduler_driver:
            scheduler_driver = CONF.scheduler_driver
        self.driver = importutils.import_object(scheduler_driver)
        super(SchedulerManager, self).__init__(service_name='scheduler',
                                               *args, **kwargs)
        self.additional_endpoints.append(_SchedulerManagerV3Proxy(self))
        
    @messaging.expected_exceptions(exception.NoValidHost)
    def select_destinations(self, context, request_spec, filter_properties):

This is the result of tracing nova scheduler code.

Adding more filter, you can put it on /schedule/filters and reconfig nova.conf to add the new filter you put.

Reference for oslo.messaging

http://www.cinlk.com/2015/12/04/rabbitmq/

import oslo.messaging
from oslo.config import cfg
class TestEndpoint(object):
    target = oslo.messaging.Target(namespace='test', version='2.0')
    def __init__(self, server):
        self.server = server
    def foo(self, ctx, id):
        return id
oslo.messaging.set_transport_defaults('myexchange')
transport = oslo.messaging.get_transport(cfg.CONF)
target = oslo.messaging.Target(topic='myroutingkey', server='myserver')
endpoints = [TestEndpoint(None)]
server = oslo.messaging.get_rpc_server(transport, target, endpoints,
                                      executor='blocking')
server.start()
server.wait()