nova 创建虚拟机

入口函数在：nova/api/openstack/computer/servers.ServersController

 def create(self, req, body):
        """Creates a new server for a given user."""

        try:
            inst_type = flavors.get_flavor_by_flavor_id(
                    flavor_id, ctxt=context, read_deleted="no")

            (instances, resv_id) = self.compute_api.create(context,
                            inst_type,
                            image_uuid,
                            display_name=name,
                            display_description=description,
                            availability_zone=availability_zone,
                            forced_host=host, forced_node=node,
                            metadata=server_dict.get('metadata', {}),
                            admin_password=password,
                            requested_networks=requested_networks,
                            check_server_group_quota=True,
                            **create_kwargs)
继续调用compute_api.create。
nova/computer/api.py
 def create(self, context, instance_type,
               image_href, kernel_id=None, ramdisk_id=None,
               min_count=None, max_count=None,
               display_name=None, display_description=None,
               key_name=None, key_data=None, security_group=None,
               availability_zone=None, forced_host=None, forced_node=None,
               user_data=None, metadata=None, injected_files=None,
               admin_password=None, block_device_mapping=None,
               access_ip_v4=None, access_ip_v6=None, requested_networks=None,
               config_drive=None, auto_disk_config=None, scheduler_hints=None,
               legacy_bdm=True, shutdown_terminate=False,
               check_server_group_quota=False):
        """Provision instances, sending instance information to the
        scheduler.  The scheduler will determine where the instance(s)
        go and will handle creating the DB entries.

        Returns a tuple of (instances, reservation_id)
        """
        
        return self._create_instance(
                       context, instance_type,
                       image_href, kernel_id, ramdisk_id,
                       min_count, max_count,
                       display_name, display_description,
                       key_name, key_data, security_group,
                       availability_zone, user_data, metadata,
                       injected_files, admin_password,
                       access_ip_v4, access_ip_v6,
                       requested_networks, config_drive,
                       block_device_mapping, auto_disk_config,
                       filter_properties=filter_properties,
                       legacy_bdm=legacy_bdm,
                       shutdown_terminate=shutdown_terminate,
                       check_server_group_quota=check_server_group_quota)
调用同一个文件中的_create_instance
   def _create_instance(self, context, instance_type,
               image_href, kernel_id, ramdisk_id,
               min_count, max_count,
               display_name, display_description,
               key_name, key_data, security_groups,
               availability_zone, user_data, metadata, injected_files,
               admin_password, access_ip_v4, access_ip_v6,
               requested_networks, config_drive,
               block_device_mapping, auto_disk_config, filter_properties,
               reservation_id=None, legacy_bdm=True, shutdown_terminate=False,
               check_server_group_quota=False):
       
        self.compute_task_api.build_instances(context,
                instances=instances, image=boot_meta,
                filter_properties=filter_properties,
                admin_password=admin_password,
                injected_files=injected_files,
                requested_networks=requested_networks,
                security_groups=security_groups,
                block_device_mapping=block_device_mapping,
                legacy_bdm=False)

        return (instances, reservation_id)
从computer 到了conduct。路径是nova/conductor/rpcapi.py
  def build_instances(self, context, instances, image, filter_properties,
            admin_password, injected_files, requested_networks,
            security_groups, block_device_mapping, legacy_bdm=True):
     
        cctxt = self.client.prepare(version=version)
        cctxt.cast(context, 'build_instances', **kw)
这边又是远程调用到/nova/conductor/manager.py

  def build_instances(self, context, instances, image, filter_properties,
            admin_password, injected_files, requested_networks,
            security_groups, block_device_mapping=None, legacy_bdm=True):
       

            self.compute_rpcapi.build_and_run_instance(context,
                    instance=instance, host=host['host'], image=image,
                    request_spec=request_spec,
                    filter_properties=local_filter_props,
                    admin_password=admin_password,
                    injected_files=injected_files,
                    requested_networks=requested_networks,
                    security_groups=security_groups,
                    block_device_mapping=bdms, node=host['nodename'],
                    limits=host['limits'])
build_instances 又通过rpc调用computer来创建虚拟机
具体路径是nova/computer/manager.py
 def build_and_run_instance(self, context, instance, image, request_spec,
                     filter_properties, admin_password=None,
                     injected_files=None, requested_networks=None,
                     security_groups=None, block_device_mapping=None,
                     node=None, limits=None):

        @utils.synchronized(instance.uuid)
        def _locked_do_build_and_run_instance(*args, **kwargs):
            # NOTE(danms): We grab the semaphore with the instance uuid
            # locked because we could wait in line to build this instance
            # for a while and we want to make sure that nothing else tries
            # to do anything with this instance while we wait.
            with self._build_semaphore:
                self._do_build_and_run_instance(*args, **kwargs)

        # NOTE(danms): We spawn here to return the RPC worker thread back to
        # the pool. Since what follows could take a really long time, we don't
        # want to tie up RPC workers.
        utils.spawn_n(_locked_do_build_and_run_instance,
                      context, instance, image, request_spec,
                      filter_properties, admin_password, injected_files,
                      requested_networks, security_groups,
                      block_device_mapping, node, limits)
这个函数最后调用spawn_n 来创建虚拟机.