1. 启动实例（start）
场景：启动处于 SHUTOFF 状态的实例
源码路径：
- API 层：
nova/compute/api.py→start() - RPC 层：
nova/compute/rpcapi.py→start_instance() - 执行层：
nova/compute/manager.py→start_instance() - 驱动层：
nova/virt/libvirt/driver.py→power_on()
关键代码：
# nova/compute/manager.py
def start_instance(self, context, instance):# 检查实例状态是否为 SHUTOFFif instance.vm_state != vm_states.STOPPED:raise exception.InstanceInvalidState(...)# 调用驱动启动虚拟机self.driver.power_on(context, instance, network_info)# 更新数据库状态为 ACTIVEinstance.vm_state = vm_states.ACTIVEinstance.save()
# nova/virt/libvirt/driver.py
def power_on(self, context, instance, network_info):# 获取 Libvirt 域对象domain = self._get_domain(instance)# 调用 Libvirt API 启动虚拟机domain.createWithFlags(libvirt.VIR_DOMAIN_START_AUTODESTROY)
2. 停止实例（stop）
场景：正常关闭处于 ACTIVE 状态的实例
源码路径：
- API 层：
nova/compute/api.py→stop() - RPC 层：
nova/compute/rpcapi.py→stop_instance() - 执行层：
nova/compute/manager.py→stop_instance() - 驱动层：
nova/virt/libvirt/driver.py→power_off()
关键代码：
# nova/compute/manager.py
def stop_instance(self, context, instance):if instance.vm_state != vm_states.ACTIVE:raise exception.InstanceInvalidState(...)# 调用驱动关闭虚拟机self.driver.power_off(instance)# 更新状态为 STOPPEDinstance.vm_state = vm_states.STOPPEDinstance.save()
# nova/virt/libvirt/driver.py
def power_off(self, instance):domain = self._get_domain(instance)# 发送 ACPI 关机信号（正常关闭）domain.shutdownFlags(libvirt.VIR_DOMAIN_SHUTDOWN_ACPI_POWER_BTN)
3. 暂停实例（pause）
场景：将运行中的实例状态冻结到内存
源码路径：
- API 层：
nova/compute/api.py→pause() - RPC 层：
nova/compute/rpcapi.py→pause_instance() - 执行层：
nova/compute/manager.py→pause_instance() - 驱动层：
nova/virt/libvirt/driver.py→pause()
关键代码：
# nova/compute/manager.py
def pause_instance(self, context, instance):if instance.vm_state != vm_states.ACTIVE:raise exception.InstanceInvalidState(...)self.driver.pause(instance)instance.vm_state = vm_states.PAUSED # 状态变为 PAUSEDinstance.save()
# nova/virt/libvirt/driver.py
def pause(self, instance):domain = self._get_domain(instance)domain.suspend() # Libvirt 暂停API
4. 恢复实例（unpause）
场景：从内存中恢复被暂停的实例
源码路径：
- API 层：
nova/compute/api.py→unpause() - RPC 层：
nova/compute/rpcapi.py→unpause_instance() - 执行层：
nova/compute/manager.py→unpause_instance() - 驱动层：
nova/virt/libvirt/driver.py→resume()
关键代码：
# nova/compute/manager.py
def unpause_instance(self, context, instance):if instance.vm_state != vm_states.PAUSED:raise exception.InstanceInvalidState(...)self.driver.resume(instance)instance.vm_state = vm_states.ACTIVE # 恢复为 ACTIVEinstance.save()
# nova/virt/libvirt/driver.py
def resume(self, instance):domain = self._get_domain(instance)domain.resume() # Libvirt 恢复API
5. 重启实例（reboot）
场景：重启运行中的实例（分软重启和硬重启）
源码路径：
- API 层：
nova/compute/api.py→reboot() - RPC 层：
nova/compute/rpcapi.py→reboot_instance() - 执行层：
nova/compute/manager.py→reboot_instance() - 驱动层：
nova/virt/libvirt/driver.py→reboot()
关键代码：
# nova/compute/manager.py
def reboot_instance(self, context, instance, reboot_type):# reboot_type: SOFT (操作系统级) / HARD (电源级)if instance.vm_state != vm_states.ACTIVE:raise exception.InstanceInvalidState(...)self.driver.reboot(context, instance, reboot_type)# 状态保持 ACTIVE
# nova/virt/libvirt/driver.py
def reboot(self, context, instance, reboot_type):domain = self._get_domain(instance)if reboot_type == "SOFT":domain.reboot(flags=0) # 发送重启信号给操作系统else: # HARDdomain.reset() # 模拟电源复位
6. 规格调整 (Resize)
6.1 API入口层
nova/api/openstack/compute/servers.py
def _action_resize(self, req, id, body):# 状态检查if instance.vm_state != vm_states.ACTIVE:raise exception.InstanceInvalidState(...)# 获取新flavorflavor_id = body['resize']['flavorRef']new_flavor = self._get_flavor(flavor_id)# 调用compute APIself.compute_api.resize(req.environ['nova.context'], instance, new_flavor)
6.2 Compute API层
nova/compute/api.py
def resize(self, context, instance, flavor):# 配额检查self._check_quota(context, cores=flavor.vcpus, ram=flavor.memory_mb)# 创建迁移记录migration = objects.Migration(context, instance_uuid=instance.uuid,source_compute=instance.host,status='migrating')migration.create()# 通过conductor发起迁移self.conductor_api.resize_instance(context, instance, migration, flavor, [])
6.3 Conductor层
nova/conductor/manager.py
def resize_instance(self, context, instance, migration, flavor, clean_shutdown):# 构建请求规格request_spec = self._build_request_spec(context, instance, flavor)# 调度目标主机hosts = self.scheduler_client.select_destinations(context, request_spec)host = hosts[0]# 调用目标节点准备self.compute_rpcapi.prep_resize(context, instance, migration, host, flavor)
6.4 目标节点准备
nova/compute/manager.py
def prep_resize(self, context, instance, migration, host, flavor):# 创建新规格实例(不启动)self.driver.spawn(context, instance, image_meta, [], block_device_info, flavor)# 更新实例状态instance.task_state = task_states.RESIZE_PREPinstance.save()
6.5 源节点迁移
nova/compute/manager.py
def resize_instance(self, context, instance, migration):# 迁移磁盘if not shared_storage:self._migrate_disk_and_power_off(context, instance, migration)# 更新实例规格instance.old_flavor = instance.flavorinstance.new_flavor = new_flavorinstance.save()# 等待用户确认instance.task_state = task_states.RESIZE_MIGRATEDinstance.save()
7. 卷管理 (Attach/Detach)
7.1 卷挂载 (Attach)
nova/compute/api.py
def attach_volume(self, context, instance, volume_id, device):# 状态检查if instance.vm_state not in (vm_states.ACTIVE, vm_states.PAUSED):raise exception.InstanceInvalidState(...)# 调用Cinder APIvolume = self.volume_api.get(context, volume_id)self.volume_api.reserve_volume(context, volume_id)# RPC调用计算节点self.compute_rpcapi.attach_volume(context, instance, volume_id, device, disk_bus)
nova/compute/manager.py
def attach_volume(self, context, instance, volume_id, device):# 获取卷连接信息connector = self.driver.get_volume_connector(instance)connection_info = self.volume_api.initialize_connection(context, volume_id, connector)# Hypervisor挂载卷self.driver.attach_volume(context, connection_info, instance, device)# 更新数据库bdm = objects.BlockDeviceMapping(context, volume_id=volume_id, instance_uuid=instance.uuid,device_name=device, connection_info=connection_info)bdm.create()
7.2 卷卸载 (Detach)
nova/compute/manager.py
def detach_volume(self, context, volume_id, instance):# 获取连接信息bdm = objects.BlockDeviceMapping.get_by_volume_id(context, volume_id)connection_info = bdm.connection_info# Hypervisor卸载卷self.driver.detach_volume(context, connection_info, instance, volume_id)# 调用Cinder APIself.volume_api.terminate_connection(context, volume_id, connection_info)self.volume_api.detach(context, volume_id)# 清理数据库bdm.destroy()
8. 添加网卡 (Add NIC)
8.1 API入口
nova/api/openstack/compute/attach_networks.py
def add(self, req, server_id, body):network_id = body['interfaceAttachment']['net_id']port_id = body['interfaceAttachment'].get('port_id')fixed_ip = body['interfaceAttachment'].get('fixed_ip')# 调用compute APIself.compute_api.attach_interface(req.environ['nova.context'], instance, network_id, port_id, fixed_ip)
8.2 Compute API层
nova/compute/api.py
def attach_interface(self, context, instance, network_id, port_id, fixed_ip):# 状态检查if instance.vm_state not in (vm_states.ACTIVE, vm_states.PAUSED):raise exception.InstanceInvalidState(...)# 创建或获取端口if port_id:port = self.network_api.show_port(context, port_id)else:port = self.network_api.create_port(context, instance.project_id, network_id, instance.uuid, fixed_ip=fixed_ip)# RPC调用计算节点self.compute_rpcapi.attach_interface(context, instance, port['id'])
8.3 计算节点执行
nova/compute/manager.py
def attach_interface(self, context, instance, port_id):# 获取网络信息network_info = self.network_api.get_instance_nw_info(context, instance)# 添加新端口new_port = self.network_api.show_port(context, port_id)network_info.append(new_port)# Hypervisor添加网卡self.driver.attach_interface(context, instance, network_info, new_port)# 更新实例网络缓存instance.info_cache.network_info = network_infoinstance.info_cache.save()
9. 冷迁移（Migrate）
冷迁移需要在实例关机状态下进行，涉及磁盘迁移和计算节点切换。
9.1 API入口层
nova/api/openstack/compute/migrate_server.py
def _migrate(self, req, id, body):# 状态检查：实例必须为ACTIVE或STOPPEDif instance.vm_state not in (vm_states.ACTIVE, vm_states.STOPPED):raise exception.InstanceInvalidState(...)# 调用compute APIself.compute_api.migrate(req.environ['nova.context'], instance)
9.2 Compute API层
nova/compute/api.py
def migrate(self, context, instance):# 检查实例是否已挂载卷if self.volume_api.get_volume_attachments(context, instance.uuid):raise exception.MigrationError(...)# 创建迁移记录migration = objects.Migration(context, instance_uuid=instance.uuid,migration_type='migration',status='migrating')migration.create()# 通过conductor发起迁移self.conductor_api.migrate_server(context, instance, migration)
9.3 Conductor调度层
nova/conductor/manager.py
def migrate_server(self, context, instance, migration):# 调度目标主机request_spec = self._build_request_spec(context, instance)hosts = self.scheduler_client.select_destinations(context, request_spec)host = hosts[0]# 调用源节点执行迁移self.compute_rpcapi.migrate_instance(context, instance, migration, host)
9.4 源节点执行
nova/compute/manager.py
def migrate_instance(self, context, instance, migration, host):# 关闭实例（如果运行中）if instance.vm_state == vm_states.ACTIVE:self.driver.power_off(instance)# 迁移磁盘self._migrate_disk(context, instance, host)# 在目标节点启动实例self.compute_rpcapi.finish_migrate_instance(context, instance, host)# 清理源实例self.driver.destroy(context, instance, [], block_device_info)
10. 热迁移（Live-Migrate）
热迁移在实例运行状态下进行，需要迁移内存状态和磁盘访问。
10.1 API入口
nova/api/openstack/compute/admin_actions.py
def _migrate_live(self, req, id, body):# 状态检查：实例必须为ACTIVEif instance.vm_state != vm_states.ACTIVE:raise exception.InstanceInvalidState(...)# 获取目标主机host = body['os-migrateLive']['host']# 调用compute APIself.compute_api.live_migrate(req.environ['nova.context'], instance, host)
10.2 Compute API层
nova/compute/api.py
def live_migrate(self, context, instance, host):# 检查目标主机是否可用service = objects.Service.get_by_host_and_binary(context, host, 'nova-compute')if not service:raise exception.ComputeHostNotFound(host=host)# 创建迁移记录migration = objects.Migration(context, instance_uuid=instance.uuid,migration_type='live-migration',status='migrating')migration.create()# 通过conductor发起热迁移self.conductor_api.live_migrate_instance(context, instance, host)
10.3 源节点执行
nova/compute/manager.py
def live_migrate_instance(self, context, instance, host):# 检查Hypervisor支持if not self.driver.capabilities['supports_live_migration']:raise exception.LiveMigrationNotSupported(...)# 执行热迁移self.driver.live_migrate(context, instance, host)# 更新实例主机instance.host = hostinstance.save()
10.4 Libvirt驱动实现
nova/virt/libvirt/driver.py
def live_migrate(self, context, instance, dest):# 获取源域domain = self._get_domain(instance)# 获取目标连接dest_uri = self._get_dest_uri(dest)# 执行迁移domain.migrateToURI(dest_uri, flags=libvirt.VIR_MIGRATE_LIVE | libvirt.VIR_MIGRATE_PEER2PEER)
11. 故障迁移（Evacuate）
故障迁移用于在计算节点宕机时将实例迁移到其他节点。
11.1 API入口
nova/api/openstack/compute/evacuate.py
def _evacuate(self, req, id, body):# 检查实例状态是否为ERRORif instance.vm_state != vm_states.ERROR:raise exception.InstanceInvalidState(...)# 获取目标主机（可选）host = body['evacuate'].get('host')# 调用compute APIself.compute_api.evacuate(req.environ['nova.context'], instance, host)
11.2 Compute API层
nova/compute/api.py
def evacuate(self, context, instance, host):# 检查源主机是否宕机source_host = instance.hostif not self.service_api.host_in_service(context, source_host):raise exception.ComputeHostNotDown(host=source_host)# 创建迁移记录migration = objects.Migration(context, instance_uuid=instance.uuid,migration_type='evacuation',status='migrating')migration.create()# 通过conductor发起迁移self.conductor_api.evacuate_instance(context, instance, host)
11.3 目标节点执行
nova/compute/manager.py
def rebuild_instance(self, context, instance, migration):# 检查共享存储if not self.driver.shared_storage:raise exception.EvacuateNotSupported(...)# 重建实例self.driver.spawn(context, instance, image_meta, network_info, block_device_info)# 更新实例状态instance.host = self.hostinstance.vm_state = vm_states.ACTIVEinstance.save()
12. 实例快照（Create Snapshot）
12.1 API入口层
nova/api/openstack/compute/servers.py
def _action_create_image(self, req, id, body):# 提取参数name = body['createImage']['name']metadata = body['createImage'].get('metadata', {})# 状态检查instance = self._get_server(context, req, id)if instance.vm_state not in (vm_states.ACTIVE, vm_states.STOPPED, vm_states.PAUSED, vm_states.SUSPENDED):raise exception.InstanceInvalidState(...)# 调用compute APIimage_id = self.compute_api.snapshot(context, instance, name, extra_properties=metadata)# 构建响应return webob.Response(location=self._get_image_location(req, image_id))
12.2 Compute API层
nova/compute/api.py
def snapshot(self, context, instance, name, extra_properties=None):# 检查配额self._check_image_quota(context, 1)# 创建Glance镜像记录image_meta = self.image_api.create(context, {'name': name,'status': 'creating','container_format': 'bare','disk_format': 'raw','properties': extra_properties or {}})# 调用conductorself.conductor_api.snapshot_instance(context, instance, image_meta['id'])return image_meta['id']
12.3 Conductor层
nova/conductor/manager.py
def snapshot_instance(self, context, instance, image_id):# 更新实例任务状态instance.task_state = task_states.IMAGE_SNAPSHOTinstance.save()# RPC调用计算节点self.compute_rpcapi.snapshot_instance(context, instance, image_id)
12.4 Compute Manager层
nova/compute/manager.py
def snapshot_instance(self, context, instance, image_id):try:# 调用驱动创建快照self.driver.snapshot(context, instance, image_id, self._legacy_nw_info(network_info))# 更新Glance状态self.image_api.update(context, image_id, {'status': 'active'})except Exception:# 失败处理self.image_api.update(context, image_id, {'status': 'killed'})raisefinally:# 清理实例状态instance.task_state = Noneinstance.save()
12.5 Hypervisor驱动层 (Libvirt)
nova/virt/libvirt/driver.py
def snapshot(self, context, instance, image_id, update_task_state):# 获取实例磁盘路径disk_path = self._get_disk_path(instance)# 创建临时快照文件with utils.tempdir() as tmpdir:snapshot_path = os.path.join(tmpdir, 'snapshot')# 执行快照命令self._create_snapshot_metadata(instance, snapshot_path)self._qemu_img_convert(disk_path, snapshot_path)# 上传到Glancewith open(snapshot_path, 'rb') as image_file:self._glance_client.call(context, 'upload', image_id, {}, image_file)
13. 快照恢复（Restore from Snapshot）
13.1 API入口层
nova/api/openstack/compute/servers.py
def create(self, req, body):# 解析请求server_dict = body['server']image_ref = server_dict.get('imageRef')# 检查是否为快照IDif image_ref and image_ref.startswith('snapshot-'):snapshot_id = image_ref.replace('snapshot-', '')# 验证快照存在self.image_api.get(context, snapshot_id)# 创建实例（与普通实例创建流程相同）return self._create_instance(req, body)
13.2 Compute API层
nova/compute/api.py
def create(self, context, instance_type, image_href, **kwargs):# 处理快照镜像if image_href and image_href.startswith('snapshot-'):snapshot_id = image_href.replace('snapshot-', '')image_meta = self.image_api.get(context, snapshot_id)image_href = image_meta['id'] # 转换为Glance镜像ID# 后续流程与普通实例创建相同self._provision_instance(context, instance_type, image_meta, ...)
13.3 Compute Manager层
nova/compute/manager.py
def _build_and_run_instance(self, context, instance, ...):# 获取镜像image_meta = self._get_image_metadata(context, instance.image_ref)# 从快照创建的特殊处理if image_meta.get('properties', {}).get('image_type') == 'snapshot':self._handle_snapshot_boot(context, instance, image_meta)# 正常启动流程self.driver.spawn(context, instance, image_meta, ...)
13.4 快照启动处理
nova/compute/manager.py
def _handle_snapshot_boot(self, context, instance, image_meta):# 检查快照元数据snapshot_properties = image_meta.get('properties', {})orig_instance_uuid = snapshot_properties.get('instance_uuid')# 恢复实例特定配置if orig_instance_uuid:orig_instance = objects.Instance.get_by_uuid(context, orig_instance_uuid)instance.key_name = orig_instance.key_nameinstance.security_groups = orig_instance.security_groupsinstance.save()
14. 删除操作（Delete）
14.1 API入口层
nova/api/openstack/compute/servers.py
def _delete(self, req, id):# 获取实例instance = self._get_server(context, req, id)# 检查状态if instance.vm_state == vm_states.DELETED:raise exception.InstanceNotFound(...)# 调用compute APIself.compute_api.delete(req.environ['nova.context'], instance)
14.2 Compute API层
nova/compute/api.py
def delete(self, context, instance):# 检查权限self._check_policy(context, 'delete', instance)# 软删除或硬删除if CONF.reclaim_instance_interval > 0:self.soft_delete(context, instance)else:self._delete(context, instance)
14.3 软删除实现
nova/compute/api.py
def soft_delete(self, context, instance):# 更新状态instance.vm_state = vm_states.SOFT_DELETEDinstance.task_state = task_states.DELETINGinstance.deleted_at = timeutils.utcnow()instance.save()# RPC调用计算节点self.compute_rpcapi.soft_delete_instance(context, instance)
14.4 硬删除实现
nova/compute/api.py
def _delete(self, context, instance):# 更新状态instance.vm_state = vm_states.DELETEDinstance.task_state = task_states.DELETINGinstance.deleted_at = timeutils.utcnow()instance.save()# RPC调用计算节点self.compute_rpcapi.terminate_instance(context, instance)
14.5 计算节点执行
nova/compute/manager.py
def terminate_instance(self, context, instance, bdms):try:# 销毁虚拟机self.driver.destroy(context, instance, network_info, bdms)# 释放网络资源self.network_api.deallocate_for_instance(context, instance)# 分离卷for bdm in bdms:if bdm.is_volume:self.volume_api.terminate_connection(context, bdm.volume_id, self._get_volume_connector())self.volume_api.detach(context, bdm.volume_id)# 清理数据库instance.destroy()except Exception:LOG.exception("终止实例失败")instance.vm_state = vm_states.ERRORinstance.save()