目录
前言
在上一篇 Openstack Nova 源码分析 — Create instances (nova-conductor阶段) 中，记录了 nova-api 接收到创建虚拟机的请求后，在 nova-conductor 中的执行流程。最终 nova-comductor 通过调用 nova-compute 的 RPC 接口函数 compute_rpcapi.build_and_run_instance() 将创建虚拟机的请求，通过 Queue 传递给 nova-compute 。本篇继续往下看看 Openstack 创建一个虚拟机时，程序流在 nova-compute 和 Virt Driver 阶段的执行过程。而且本篇使用 VCDirver 作为Virt Driver Type 。
NOTE:下面的代码块大多为节选。
流程图
nova-compute & vCenter
在之前的文章 VMware 接入 Openstack — 使用 Openstack 创建 vCenter 虚拟机 已经记录过如何将 VMware 接入 Openstack ，本质是通过 nova-compute 和 vCenter 中的 Cluster 一一对应来进行管理。
紧接着，当 nova-conductor 调用了 nova-compute 的 RPC 接口后，相应接口的具体操作函数在 nova.compute.manager 中实现。
# nova/compute/manager.py
1841 def build_and_run_instance(self, context, instance, image, request_spec,
1 filter_properties, admin_password=None,
2 injected_files=None, requested_networks=None,
3 security_groups=None, block_device_mapping=None,
4 node=None, limits=None):
5
6 @utils.synchronized(instance.uuid)
7 def _locked_do_build_and_run_instance(*args, **kwargs):
8 # NOTE(danms): We grab the semaphore with the instance uuid
9 # locked because we could wait in line to build this instance
10 # for a while and we want to make sure that nothing else tries
11 # to do anything with this instance while we wait.
12 with self._build_semaphore:
13 self._do_build_and_run_instance(*args, **kwargs)
14
15 # NOTE(danms): We spawn here to return the RPC worker thread back to
16 # the pool. Since what follows could take a really long time, we don't
17 # want to tie up RPC workers.
18 utils.spawn_n(_locked_do_build_and_run_instance,
19 context, instance, image, request_spec,
20 filter_properties, admin_password, injected_files,
21 requested_networks, security_groups,
22 block_device_mapping, node, limits)在上述的 nova.compute.manager.ComputeManager:build_and_run_instance()中调用了_do_build_and_run_instance() 函数。
# nova/compute/manager.py
1870 def _do_build_and_run_instance(self, context, instance, image,
1 request_spec, filter_properties, admin_password, injected_files,
2 requested_networks, security_groups, block_device_mapping,
3 node=None, limits=None):
...
1901 try:
1 self._build_and_run_instance(context, instance, image,
2 decoded_files, admin_password, requested_networks,
3 security_groups, block_device_mapping, node, limits,
4 filter_properties)
5 return build_results.ACTIVE再跳转到 _build_and_run_instance()，这个函数非常重要。
# nova/compute/manager.py
93 from nova.virt import driver
667 class ComputeManager(manager.Manager):
677 def __init__(self, compute_driver=None, *args, **kwargs):
679 self.virtapi = ComputeVirtAPI(self)
718 self.driver = driver.load_compute_driver(self.virtapi, compute_driver)
# 加载 Driver, 过程如下：
# nova.virt.driver:load_compute_driver()
# ==> oslo_utils.importutils:import_object_ns()
# ==> nova.utils:check_isinstance()
# Return： 一个由 (compute_driver = CONF.compute_driver) 决定的 ComputeDriver 实例化对象 driver
1979 def _build_and_run_instance(self, context, instance, image, injected_files,
1 admin_password, requested_networks, security_groups,
2 block_device_mapping, node, limits, filter_properties):
########## Get image_id
1983 image_name = image.get('name')
# ==> nova.image.__init__
# ==> nova.image.api.API:get()
# ==> nova.image.api.API:_get_session_and_image_id()
# ==> nova.image.glance:get_remote_image_service()
# ==> nova.image.glance.GlanceImageService:show()
# ==> nova.image.glance._tnslate_from_glanceranslate_from_glance
# Return:ClanceImageService.show() 返回一个包含了 Image_Mete 信息的 Dict['name'] == uri_or_id
1 self._notify_about_instance_usage(context, instance, 'create.start',
2 extra_usage_info={'image_name': image_name})
# 向外部发出一个 start to create instance 的通知
########## 应用 claim 机制 Update table:compute_nodes
1986 try:
1 rt = self._get_resource_tracker(node)
2 with rt.instance_claim(context, instance, limits):
# 通过传参来创建资源Dict (EG. network_info/block_device_info)
1994 with self._build_resources(context, instance,
1 requested_networks, security_groups, image,
2 block_device_mapping) as resources:
# Change the Instance status
3 instance.vm_state = vm_states.BUILDING
4 instance.task_state = task_states.SPAWNING
2 # NOTE(JoshNang) This also saves the changes to the
3 # instance from _allocate_network_async, as they aren't
4 # saved in that function to prevent races.
5 instance.save(expected_task_state=
6 task_states.BLOCK_DEVICE_MAPPING)
# Block Storage(cinder)
2004 block_device_info = resources['block_device_info']
# Network
2005 network_info = resources['network_info']
########## Create Instance
# 由 nova.virt.driver.ComputeDriver 实例化对象 driver 调用 spawn（） 函数来进行虚拟机的创建
2006 self.driver.spawn(context, instance, image,
1 injected_files, admin_password,
2 network_info=network_info,
3 block_device_info=block_device_info)NOTE：task states 执行 Task 时的过渡状态，在状态发生改变时会向外部发出通知。前提是配置项notify_on_state_change要配置为vm_state或vm_and_task_state(有待验证)。
因为我希望使用 VCDriver 驱动类型， 所以在 Nova 的配置文件 /etc/nova.conf 中设置选项compute_driver=vmwareapi.VMwareVCDriver。
这样的话，通过执行代码 compute_driver = CONF.compute_driver 就可以获得 VCDriver 的 driver 对象。当我们使用这个 driver 对象来创建虚拟机时，程序流会进入到nova/virt/vmwareapi/ 再通过调用 VMware 提供的 API 接口 (nova.virt.vmwareapi.driver.VMwareVCDriver:spawn())来最终实现虚拟机的创建 。
# nova/virt/vmwareapi/driver.py
46 from nova.virt.vmwareapi import vmops
125 class VMwareVCDriver(driver.ComputeDriver):
1 """The VC host connection object."""
148 def __init__(self, virtapi, scheme="https"):
166 self._session = VMwareAPISession(scheme=scheme)
# 实例化了一个 vmops.VMwareVMOps 对象
186 self._vmops = vmops.VMwareVMOps(self._session,
1 virtapi,
2 self._volumeops,
3 self._cluster_ref,
4 datastore_regex=self._datastore_regex)
401 def spawn(self, context, instance, image_meta, injected_files,
1 admin_password, network_info=None, block_device_info=None):
2 """Create VM instance."""
3 image_meta = objects.ImageMeta.from_dict(image_meta)
# nova.object.image_meta.ImageMeta:from_dict()
# ==> nova.object.image_meta.ImageMetaProps:from_dict()
# Return： obj = cls() = image_meta.get("properties", {})[0]
# _vmops 为 nova.virt.vmmwareapi.vmops.VMwareVMOps 的实例化对象
4 self._vmops.spawn(context, instance, image_meta, injected_files,
5 admin_password, network_info, block_device_info)
跳转到 nova.virt.vmwareapi.vmops.VMwareVMOps:spawn()
# nova/virt/vmwareapi/vmops.py
62 from nova.virt.vmwareapi import vm_util
# 这一个类封装了对 vCenter 的虚拟机的操作函数(EG. _get_base_folder/_extend_virtual_disk/_delete_datastore_file/build_virtual_machine)
149 class VMwareVMOps(object):
1 """Management class for VM-related tasks."""
152 def __init__(self, session, virtapi, volumeops, cluster=None,
1 datastore_regex=None):
677 def spawn(self, context, instance, image_meta, injected_files,
1 admin_password, network_info, block_device_info=None):
2
3 client_factory = self._session.vim.client.factory
4 image_info = images.VMwareImage.from_image(instance.image_ref,
5 image_meta)
# nova.virt.vmwareapi.images.VMwareImage:from_image()
# """Returns VMwareImage, the subset of properties the driver uses."""
# Return vmware image object
# 在这里类中，实现了一系列关于 Image 属性参数的设定和克隆 。
685 vi = self._get_vm_config_info(instance, image_info,
1 extra_specs)
# 获取创建虚拟机所需要的参数信息(EG. ds/dc)
# nova.virt.vmwareapi.vmops._get_vm_config_info()
# Return： VirtualMachineInstanceConfigInfo()
691 vm_ref = self.build_virtual_machine(instance,
1 image_info,
2 vi.dc_info,
3 vi.datastore,
4 network_info,
5 extra_specs,
6 metadata)继续跳转到 nova.virt.vmwareapi.vmopss.VMwareVMOps:build_virtual_machine() 。
277 def build_virtual_machine(self, instance, image_info,
1 dc_info, datastore, network_info, extra_specs,
2 metadata):
3 vif_infos = vmwarevif.get_vif_info(self._session,
4 self._cluster,
5 utils.is_neutron(),
6 image_info.vif_model,
7 network_info)
# 获取 Virtual Interface info
# nova.virt.vmwareapi.vif:get_vif_info()
# ==> nova.virt.vmwareapi.vif:get_vif_dict()
#Return: vif_info 包含了(netowork_name/mac_address/network_ref/iface_id/cif_model)等信息
8
9 if extra_specs.storage_policy:
10 profile_spec = vm_util.get_storage_profile_spec(
11 self._session, extra_specs.storage_policy)
12 else:
13 profile_spec = None
14 # Get the create vm config spec
15 client_factory = self._session.vim.client.factory
16 config_spec = vm_util.get_vm_create_spec(client_factory,
17 instance,
18 datastore.name,
19 vif_infos,
20 extra_specs,
21 image_info.os_type,
22 profile_spec=profile_spec,
23 metadata=metadata)
# 获取虚拟机的 config_spec (profile/cpu/memory/Neutron 等)
# nova.virt.vmwareapi.vmm_util.get_vm_create_spec（）
24 # Create the VM
# create_vm() 会返回 Task 的 Result ，并附值给 vm_ref。 vm_ref 被用于创建虚拟机后的一切列数据更新 。
25 vm_ref = vm_util.create_vm(self._session, instance, dc_info.vmFolder,
26 config_spec, self._root_resource_pool)
27 return vm_ref在 VMwareVMOps:build_virtual_machine() 函数中又调用了 nova.virt.vmwareapi.vm_util:get_vm_create_spec() 函数来获取创建虚拟机所需要的参数信息。同时也调用了nova.virt.vmwareapi.vm_util:create_vm() 来 Create the VM 。所以我们先转到 nova.virt.vmwareapi.vm_util Module 去看看具体的 Return 。
# nova/virt/vmwareapi/vm_util.py
"""
The VMware API VM utility module to build SOAP object specs.
"""
1287 def create_vm(session, instance, vm_folder, config_spec, res_pool_ref):
1 """Create VM on ESX host."""
2 LOG.debug("Creating VM on the ESX host", instance=instance)
# session 是 nova.virt.vmwareapi.driver.VMwareAPISession 的实例化对象
3 vm_create_task = session._call_method(
4 session.vim,
5 "CreateVM_Task", vm_folder,
6 config=config_spec, pool=res_pool_ref)
7 try:
8 task_info = session._wait_for_task(vm_create_task)
9 except vexc.VMwareDriverException:
10 # An invalid guestId will result in an error with no specific fault
11 # type and the generic error 'A specified parameter was not correct'.
12 # As guestId is user-editable, we try to help the user out with some
13 # additional information if we notice that guestId isn't in our list of
14 # known-good values.
15 # We don't check this in advance or do anything more than warn because
16 # we can't guarantee that our list of known-good guestIds is complete.
17 # Consequently, a value which we don't recognise may in fact be valid.
18 with excutils.save_and_reraise_exception():
19 if config_spec.guestId not in constants.VALID_OS_TYPES:
20 LOG.warning(_LW('vmware_ostype from image is not recognised: '
21 '\'%(ostype)s\'. An invalid os type may be '
22 'one cause of this instance creation failure'),
23 {'ostype': config_spec.guestId})
24 LOG.debug("Created VM on the ESX host", instance=instance)
25 return task_info.result
# 这个函数的最终返回 Task 的执行结果到此为止关于虚拟机的创建就完成了，需要注意的是：在我们创建完虚拟机之后其实还有许多的事情是需要做的，EG. 更新数据库/开启虚拟机
所以，在nova.virt.vmwareapi.vm_util:create_vm() 中得到了创建虚拟机的 Task Result task_info.result 之后，需要使用这一 Return 来进行一系列的操作。当然，这一系列的操作会在 VM 相关任务管理类： nova.virt.vmwareapi.wmops.VMwareVMOps 中实现。
# nova/virt/vmmwareapi/vmops.py
# 下面的操作，都是在成功创建了虚拟机并接收 vm_ref (vm_ref = vm_util.create_vm())返回值之后执行。
2 # Cache the vm_ref. This saves a remote call to the VC. This uses the
1 # instance uuid.
701 vm_util.vm_ref_cache_update(instance.uuid, vm_ref)
2 # Set the machine.id parameter of the instance to inject
1 # the NIC configuration inside the VM
708 if CONF.flat_injected:
1 self._set_machine_id(client_factory, instance, network_info,
2 vm_ref=vm_ref)
2 # Set the vnc configuration of the instance, vnc port starts from 5900
1 if CONF.vnc.enabled:
714 self._get_and_set_vnc_config(client_factory, instance, vm_ref)
6 if instance.image_ref:
5 self._imagecache.enlist_image(
4 image_info.image_id, vi.datastore, vi.dc_info.ref)
3 self._fetch_image_if_missing(context, vi)
2
1 if image_info.is_iso:
727 self._use_iso_image(vm_ref, vi)
1 elif image_info.linked_clone:
2 self._use_disk_image_as_linked_clone(vm_ref, vi)
3 else:
4 self._use_disk_image_as_full_clone(vm_ref, vi)
1 # Create ephemeral disks
758 self._create_ephemeral(block_device_info, instance, vm_ref,
1 vi.dc_info, vi.datastore, instance.uuid,
2 vi.ii.adapter_type)
3 self._create_swap(block_device_info, instance, vm_ref, vi.dc_info,
4 vi.datastore, instance.uuid, vi.ii.adapter_type)
764 if configdrive.required_by(instance):
1 self._configure_config_drive(
2 instance, vm_ref, vi.dc_info, vi.datastore,
3 injected_files, admin_password, network_info)
# 将虚拟机起电
769 vm_util.power_on_instance(self._session, instance, vm_ref=vm_ref)
