• 查看这种类型的instance是否达到最大值
• 如果不存在安全组，就创建个
• 生成MAC地址和hostnames
• 给scheduler发送一个消息去运行这个实例

1. def _schedule_run_instance(self,
2. ...
3. return rpc_method(context,
4. FLAGS.scheduler_topic,
5. {"method": "run_instance",
6. "args": {"topic": FLAGS.compute_topic,
7. "request_spec": request_spec,
8. "admin_password": admin_password,
9. "injected_files": injected_files,
10. "requested_networks": requested_networks,
11. "is_first_time": True,
12. "filter_properties": filter_properties}})

1. def cast_to_compute_host(context, host, method, update_db=True, **kwargs):
2. """Cast request to a compute host queue"""
3. if update_db:
4. # fall back on the id if the uuid is not present
5. instance_id = kwargs.get('instance_id', None)
6. instance_uuid = kwargs.get('instance_uuid', instance_id)
7. if instance_uuid is not None:
8. now = utils.utcnow()
9. db.instance_update(context, instance_uuid,
10. {'host': host, 'scheduled_at': now})
11. rpc.cast(context,
12. db.queue_get_for(context, 'compute', host),
13. {"method": method, "args": kwargs})
14. LOG.debug(_("Casted '%(method)s' to compute '%(host)s'") % locals())

1. def _run_instance(self, context, instance_uuid,
2. requested_networks=None,
3. injected_files=[],
4. admin_password=None,
5. is_first_time=False,
6. **kwargs):
7. """Launch a new instance with specified options."""
8. context = context.elevated()
9. try:
10. instance = self.db.instance_get_by_uuid(context, instance_uuid)
11. self._check_instance_not_already_created(context, instance)
12. image_meta = self._check_image_size(context, instance)
13. self._start_building(context, instance)
14. self._notify_about_instance_usage(instance, "create.start")
15. network_info = self._allocate_network(context, instance,
16. requested_networks)
17. try:
18. block_device_info = self._prep_block_device(context, instance)
19. instance = self._spawn(context, instance, image_meta,
20. network_info, block_device_info,
21. injected_files, admin_password)
22. ...

1. def allocate_for_instance(self, context, instance, **kwargs):
2. """Allocates all network structures for an instance.
3. :returns: network info as from get_instance_nw_info() below
4. """
5. args = kwargs
6. args['instance_id'] = instance['id']
7. args['instance_uuid'] = instance['uuid']
8. args['project_id'] = instance['project_id']
9. args['host'] = instance['host']
10. args['rxtx_factor'] = instance['instance_type']['rxtx_factor']
11. nw_info = rpc.call(context, FLAGS.network_topic,
12. {'method': 'allocate_for_instance',
13. 'args': args})

1. def spawn(self, context, instance, image_meta, network_info,
2. block_device_info=None):
3. xml = self.to_xml(instance, network_info, image_meta, False,
4. block_device_info=block_device_info)
5. self.firewall_driver.setup_basic_filtering(instance, network_info)
6. self.firewall_driver.prepare_instance_filter(instance, network_info)
7. self._create_image(context, instance, xml, network_info=network_info,
8. block_device_info=block_device_info)
9. self._create_new_domain(xml)
10. LOG.debug(_("Instance is running"), instance=instance)
11. self._enable_hairpin(instance)
12. self.firewall_driver.apply_instance_filter(instance, network_info)
13. def _wait_for_boot():
14. """Called at an interval until the VM is running."""
15. try:
16. state = self.get_info(instance)['state']
17. except exception.NotFound:
18. LOG.error(_("During reboot, instance disappeared."),
19. instance=instance)
20. raise utils.LoopingCallDone
21. if state == power_state.RUNNING:
22. LOG.info(_("Instance spawned successfully."),
23. instance=instance)
24. raise utils.LoopingCallDone
25. timer = utils.LoopingCall(_wait_for_boot)
26. return timer.start(interval=0.5, now=True)

• 通过libvirt xml文件，然后根据xml文件生成instance
• 准备network filter，默认的fierwall driver是iptables
• image的创建(详细情况以后再介绍)

def _create_image(self, context, instance, libvirt_xml, suffix='',

• 最后虚拟化driver的spawn()方法中调用driver 的creatXML()