做个一个没怎么学过python的菜鸟,看源码是最好的学习方式了,现在就从nova入手,主要注释一下 nova/compute/api.py 中的 create_instance函数
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_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, reservation_id=None, create_instance_here=False, scheduler_hints=None): """Verify all the input parameters regardless of the provisioning strategy being performed and schedule the instance(s) for creation.""" if not metadata: metadata = {} if not display_description: display_description = '' if not security_group: security_group = 'default' if not instance_type: instance_type = instance_types.get_default_instance_type() if not min_count: min_count = 1 if not max_count: max_count = min_count if not metadata: metadata = {} block_device_mapping = block_device_mapping or [] #从quota得到具体的实例限制 num_instances = quota.allowed_instances(context, max_count, instance_type) if num_instances < min_count: pid = context.project_id if num_instances <= 0: msg = _("Cannot run any more instances of this type.") else: msg = (_("Can only run %s more instances of this type.") % num_instances) LOG.warn(_("Quota exceeded for %(pid)s," " tried to run %(min_count)s instances. " + msg) % locals()) raise exception.QuotaError(code="InstanceLimitExceeded") #检查元数据、注入文件、网络 self._check_metadata_properties_quota(context, metadata) self._check_injected_file_quota(context, injected_files) self._check_requested_networks(context, requested_networks) (image_service, image_id) = nova.image.get_image_service(context, image_href) #通过镜像id,访问镜像的具体服务。得到一个image字典。 image = image_service.show(context, image_id) #iamge 是一个字典,返回key='min_ram'对应的值, get是字典的一个方法。 #memory_mb:是虚拟机所属内存。 if instance_type['memory_mb'] < int(image.get('min_ram') or 0): raise exception.InstanceTypeMemoryTooSmall() #root_gb :虚拟机根硬盘大小;instance_type代表了创建虚拟机的需求或者说配置,image则是实际上存在镜像的一个东西。 if instance_type['root_gb'] < int(image.get('min_disk') or 0): raise exception.InstanceTypeDiskTooSmall() config_drive_id = None if config_drive and config_drive is not True: # config_drive is volume id config_drive, config_drive_id = None, config_drive os_type = None #properties是字典image的一个属性,image[properties]又是一个字典。 if 'properties' in image and 'os_type' in image['properties']: os_type = image['properties']['os_type'] architecture = None if 'properties' in image and 'arch' in image['properties']: architecture = image['properties']['arch'] vm_mode = None if 'properties' in image and 'vm_mode' in image['properties']: vm_mode = image['properties']['vm_mode'] # If instance doesn't have auto_disk_config overridden by request, use # whatever the image indicates if auto_disk_config is None: if ('properties' in image and 'auto_disk_config' in image['properties']): #bool_from_str:将字符串转化为数组 auto_disk_config = utils.bool_from_str( image['properties']['auto_disk_config']) if kernel_id is None: kernel_id = image['properties'].get('kernel_id', None) if ramdisk_id is None: ramdisk_id = image['properties'].get('ramdisk_id', None) # FIXME(sirp): is there a way we can remove null_kernel? # No kernel and ramdisk for raw images if kernel_id == str(FLAGS.null_kernel): kernel_id = None ramdisk_id = None LOG.debug(_("Creating a raw instance")) # Make sure we have access to kernel and ramdisk (if not raw) #locals() 返回一个名字/值对的字典 LOG.debug(_("Using Kernel=%(kernel_id)s, Ramdisk=%(ramdisk_id)s") % locals()) #show具体是干嘛的???? if kernel_id: image_service.show(context, kernel_id) if ramdisk_id: image_service.show(context, ramdisk_id) if config_drive_id: image_service.show(context, config_drive_id) #检查是否具有安全防火墙,如果不具有就创建一个默认的安全组。 self.ensure_default_security_group(context) #ssh 密钥文件名存在,但是数据不存在。 if key_data is None and key_name: key_pair = self.db.key_pair_get(context, context.user_id, key_name) key_data = key_pair['public_key'] if reservation_id is None: reservation_id = utils.generate_uid('r') #根设备名 root_device_name = block_device.properties_root_device_name( image['properties']) # NOTE(vish): We have a legacy hack to allow admins to specify hosts # via az using az:host. It might be nice to expose an # api to specify specific hosts to force onto, but for # now it just supports this legacy hack. host = None #parition 函数进行分割字符串,如果分割成功,返回tuple,中间的为分隔符;如果找不到,返回1个有用字符串 #剩余两个元素为空。 #下边主要功能是设置调度集群。 if availability_zone: availability_zone, _x, host = availability_zone.partition(':') if not availability_zone: availability_zone = FLAGS.default_schedule_zone if context.is_admin and host: filter_properties = {'force_hosts': [host]} else: filter_properties = {} filter_properties['scheduler_hints'] = scheduler_hints base_options = { 'reservation_id': reservation_id, 'image_ref': image_href, 'kernel_id': kernel_id or '', 'ramdisk_id': ramdisk_id or '', 'power_state': power_state.NOSTATE, 'vm_state': vm_states.BUILDING, #注意刚开始是创建中状态。 'config_drive_id': config_drive_id or '', 'config_drive': config_drive or '', 'user_id': context.user_id, 'project_id': context.project_id, 'launch_time': time.strftime('%Y-%m-%dT%H:%M:%SZ', time.gmtime()),#格式化一个时间字符串。 'instance_type_id': instance_type['id'],#虚拟机的套餐类型。 'memory_mb': instance_type['memory_mb'],#虚拟机的内存 'vcpus': instance_type['vcpus'],#虚拟机的cpu核数。 'root_gb': instance_type['root_gb'],#虚机根硬盘大小 'ephemeral_gb': instance_type['ephemeral_gb'], 'display_name': display_name, 'display_description': display_description, 'user_data': user_data or '', 'key_name': key_name,#密钥文件名 'key_data': key_data,#密钥数据 'locked': False, 'metadata': metadata, 'access_ip_v4': access_ip_v4, 'access_ip_v6': access_ip_v6, 'availability_zone': availability_zone, 'os_type': os_type,#操作系统类型。 'architecture': architecture, 'vm_mode': vm_mode,#虚机状态。 'root_device_name': root_device_name,#根设备名称。 'progress': 0, 'auto_disk_config': auto_disk_config} LOG.debug(_("Going to run %s instances...") % num_instances) if create_instance_here: instance = self.create_db_entry_for_new_instance( context, instance_type, image, base_options, security_group, block_device_mapping) # Tells scheduler we created the instance already. base_options['uuid'] = instance['uuid'] #cast是单向的不需要等待对方回复即可返回。 rpc_method = rpc.cast else: # We need to wait for the scheduler to create the instance # DB entries, because the instance *could* be # created in # a child zone. #我的理解:该实例不一定在这个集群创建,可能去子集群,因为可能有很多个吧 #因此需要等待他的创建完成。 rpc_method = rpc.call # TODO(comstud): We should use rpc.multicall when we can # retrieve the full instance dictionary from the scheduler. # Otherwise, we could exceed the AMQP max message size limit. # This would require the schedulers' schedule_run_instances # methods to return an iterator vs a list. #这里应该是调度器发消息了,让调度器去通知具体节点的nova-compute进程去创建虚机。 instances = self._schedule_run_instance( rpc_method, context, base_options, instance_type, availability_zone, injected_files, admin_password, image, num_instances, requested_networks, block_device_mapping, security_group, filter_properties) #这里创建完毕,返回instance实例。 if create_instance_here: return ([instance], reservation_id) return (instances, reservation_id)
下边这个是给调度器发送instance创建消息的函数:_schedule_run_instance
#create_instance 调用,发送消息给调度器 def _schedule_run_instance(self, rpc_method, context, base_options, instance_type, availability_zone, injected_files, admin_password, image, num_instances, requested_networks, block_device_mapping, security_group, filter_properties): """Send a run_instance request to the schedulers for processing.""" #pid不是进程id,是项目id..... pid = context.project_id uid = context.user_id LOG.debug(_("Sending create to scheduler for %(pid)s/%(uid)s's") % locals()) request_spec = { 'image': utils.to_primitive(image), 'instance_properties': base_options, 'instance_type': instance_type, 'num_instances': num_instances, 'block_device_mapping': block_device_mapping, 'security_group': security_group, } return rpc_method(context, FLAGS.scheduler_topic, {"method": "run_instance", "args": {"topic": FLAGS.compute_topic, "request_spec": request_spec, "admin_password": admin_password, "injected_files": injected_files, "requested_networks": requested_networks, "is_first_time": True, "filter_properties": filter_properties}})
这个代码是我个人的理解。最进学习openstack感觉一头雾水,边看《云计算与openstack》边写一些东西出来,也是一种体验吧。加油!!!!
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时间: 2024-10-30 21:21:51