源码版本：H版
以nova-api为起点开始分析！
一、在nova-api进程中进行处理
根据对nova api的分析，当请求发过来的时候，由相应的Controller进行处理，此处如下：
nova/api/openstack/compute/servers.py
Controller类：
@wsgi.response(202)
@wsgi.serializers(xml=FullServerTemplate)
@wsgi.deserializers(xml=CreateDeserializer)
def create(self, req, body):
try:
_get_inst_type = flavors.get_flavor_by_flavor_id
inst_type = _get_inst_type(flavor_id, ctxt=context,
read_deleted="no")
(instances, resv_id) = self.compute_api.create(context,
...
legacy_bdm=legacy_bdm)
...
这里需要发现self.compute_api究竟为哪个类的对象。从Controller类的__init__函数中发现：
"""compute指nova.compute"""
self.compute_api = compute.API()
nova/compute/__init__.py
def API(*args, **kwargs):
importutils = nova.openstack.common.importutils
"""此处class_name为nova.compute.api.API"""
class_name = _get_compute_api_class_name()
"""创建nova.compute.api.API类对象并返回"""
return importutils.import_object(class_name, *args, **kwargs)
所以self.compute_api即为nova.compute.api.API类的对象。
1、接着看self.compute_api的create函数调用
nova/compute/api.py
API类:
@hooks.add_hook("create_instance")
def create(self, context, instance_type,
...):
...
return self._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,
reservation_id=None, scheduler_hints=None,
legacy_bdm=True):
...
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)
这里需要分析self.compute_task_api为哪个类的对象，代码分析如下：
nova/compute/api.py
API类：
@property
def compute_task_api(self):
if self._compute_task_api is None:
from nova import conductor
self._compute_task_api = conductor.ComputeTaskAPI()
return self._compute_task_api
nova/conductor/__init__.py
def ComputeTaskAPI(*args, **kwargs):
use_local = kwargs.pop('use_local', False)
if oslo.config.cfg.CONF.conductor.use_local or use_local:
api = conductor_api.LocalComputeTaskAPI
else:
"""conductor_api为nova.conductor.api"""
api = conductor_api.ComputeTaskAPI
return api(*args, **kwargs)
所以self.compute_task_api为nova.conductor.api.ComputeTaskAPI类的对象。
2、接着看self.compute_task_api的build_instances函数
nova/conductor/api.py
ComputeTaskAPI类：
def build_instances(self, context, instances, image, filter_properties,
admin_password, injected_files, requested_networks,
security_groups, block_device_mapping, legacy_bdm=True):
self.conductor_compute_rpcapi.build_instances(context,
instances=instances, image=image,
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=legacy_bdm)
其中，self.conductor_compute_rpcapi= rpcapi.ComputeTaskAPI() !
3、接着看self.conductor_compute_rpcapi的build_instances函数
nova/conductor/rpcapi.py
ComputeTaskAPI类：
def build_instances(self, context, instances, image, filter_properties,
admin_password, injected_files, requested_networks,
security_groups, block_device_mapping, legacy_bdm=True):
instances_p = [jsonutils.to_primitive(inst) for inst in instances]
image_p = jsonutils.to_primitive(image)
cctxt = self.client.prepare(version='1.5')
cctxt.cast(context, 'build_instances',
instances=instances_p, image=image_p,
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=legacy_bdm)
其中self.client = self.get_client(namespace=self.RPC_API_NAMESPACE)，即 cctxt = self.client.prepare(version='1.5')调用后cctxt为nova.rpcclient.RPCClient，根据http://www.cnblogs.com/littlebugfish/p/4058007.html中简述的消息队列调用原理，这里将转到nova-conductor进程中进行处理。
二、在nova-conductor进程中进行处理
nova/conductor/manager.py
ComputeTaskManager类：
def build_instances(self, context, instances, image, filter_properties,
admin_password, injected_files, requested_networks,
security_groups, block_device_mapping, legacy_bdm=True):
...
self.scheduler_rpcapi.run_instance(context, request_spec=request_spec,
admin_password=admin_password, injected_files=injected_files,
requested_networks=requested_networks, is_first_time=True,
filter_properties=filter_properties,
legacy_bdm_in_spec=legacy_bdm)
其中，self.scheduler_rpcapi = scheduler_rpcapi.SchedulerAPI(),而scheduler_rpcapi为nova.scheduler.rpcapi,则self.scheduler_rpcapi为nova.scheduler.rpcapi.SchedulerAPI类的对象，接着看代码如下：
nova/scheduler/rpcapi.py
SchedulerAPI类:
def run_instance(self, ctxt, request_spec, admin_password,
injected_files, requested_networks, is_first_time,
filter_properties, legacy_bdm_in_spec=True):
version = '2.0'
msg_kwargs = {'request_spec': request_spec,
'admin_password': admin_password,
'injected_files': injected_files,
'requested_networks': requested_networks,
'is_first_time': is_first_time,
'filter_properties': filter_properties}
if self.client.can_send_version('2.9'):
version = '2.9'
msg_kwargs['legacy_bdm_in_spec'] = legacy_bdm_in_spec
cctxt = self.client.prepare(version=version)
return cctxt.cast(ctxt, 'run_instance', **msg_kwargs)
根据http://www.cnblogs.com/littlebugfish/p/4058007.html中简述的消息队列调用原理，这里将转到nova-scheduler进程中进行处理。
三、在nova-scheduler进程中进行处理
nova/scheduler/manager.py
SchedulerManager类：
def run_instance(self, context, request_spec, admin_password,
injected_files, requested_networks, is_first_time,
filter_properties, legacy_bdm_in_spec=True):
instance_uuids = request_spec['instance_uuids']
with compute_utils.EventReporter(context, conductor_api.LocalAPI(),
'schedule', *instance_uuids):
try:
return self.driver.schedule_run_instance(context,
request_spec, admin_password, injected_files,
requested_networks, is_first_time, filter_properties,
legacy_bdm_in_spec)
...
这里需要看self.driver究竟为哪个类的对象。在SchedulerManager类的__init__函数中，有如下代码：
if not scheduler_driver:
scheduler_driver = CONF.scheduler_driver
self.driver = importutils.import_object(scheduler_driver)
根据配置，CONF.scheduler_driver为nova.scheduler.filter_scheduler.FilterScheduler，所以self.driver为nova.scheduler.filter_scheduler.FilterScheduler类的对象，所以接下来看：
nova.scheduler.filter_scheduler.py
FilterScheduler类：
def schedule_run_instance(self, context, request_spec,
admin_password, injected_files,
requested_networks, is_first_time,
filter_properties, legacy_bdm_in_spec):
...
"""选用来创建虚拟机的主机"""
weighed_hosts = self._schedule(context, request_spec,
filter_properties, instance_uuids)
...
for num, instance_uuid in enumerate(instance_uuids):
request_spec['instance_properties']['launch_index'] = num
try:
try:
weighed_host = weighed_hosts.pop(0)
LOG.info(_("Choosing host %(weighed_host)s "
"for instance %(instance_uuid)s"),
{'weighed_host': weighed_host,
'instance_uuid': instance_uuid})
except IndexError:
raise exception.NoValidHost(reason="")
"""创建虚拟机"""
self._provision_resource(context, weighed_host,
request_spec,
filter_properties,
requested_networks,
injected_files, admin_password,
is_first_time,
instance_uuid=instance_uuid,
legacy_bdm_in_spec=legacy_bdm_in_spec)
except Exception as ex:
driver.handle_schedule_error(context, ex, instance_uuid,
request_spec)
retry = filter_properties.get('retry', {})
retry['hosts'] = []
self.notifier.info(context, 'scheduler.run_instance.end', payload)
1、 选择用来创建虚拟机的主机，代码如下：
weighed_hosts = self._schedule(context, request_spec,
filter_properties, instance_uuids)
接着看_schedule函数，如下：
def _schedule(self, context, request_spec, filter_properties,
instance_uuids=None):
...
hosts = self.host_manager.get_all_host_states(elevated)
selected_hosts = []
if instance_uuids:
num_instances = len(instance_uuids)
else:
num_instances = request_spec.get('num_instances', 1)
for num in xrange(num_instances):
"""根据规则过滤掉特定的主机。例如可以设定忽略某些主机，这样就不会选择这些主机来创建虚拟机"""
hosts = self.host_manager.get_filtered_hosts(hosts,
filter_properties, index=num)
if not hosts:
break
LOG.debug(_("Filtered %(hosts)s"), {'hosts': hosts})
"""根据规则为候选主机分配权重以便选取最佳的主机创建虚拟机，此处暂时不详述权重分配的过程"""
weighed_hosts = self.host_manager.get_weighed_hosts(hosts,
filter_properties)
LOG.debug(_("Weighed %(hosts)s"), {'hosts': weighed_hosts})
scheduler_host_subset_size = CONF.scheduler_host_subset_size
if scheduler_host_subset_size > len(weighed_hosts):
scheduler_host_subset_size = len(weighed_hosts)
if scheduler_host_subset_size < 1:
scheduler_host_subset_size = 1
chosen_host = random.choice(
weighed_hosts[0:scheduler_host_subset_size])
selected_hosts.append(chosen_host)
chosen_host.obj.consume_from_instance(instance_properties)
if update_group_hosts is True:
filter_properties['group_hosts'].append(chosen_host.obj.host)
return selected_hosts
2、开始创建虚拟机，代码如下：
self._provision_resource(context, weighed_host,
request_spec,
filter_properties,
requested_networks,
injected_files, admin_password,
is_first_time,
instance_uuid=instance_uuid,
legacy_bdm_in_spec=legacy_bdm_in_spec)
接着看_provision_resource函数，如下：
def _provision_resource(self, context, weighed_host, request_spec,
filter_properties, requested_networks, injected_files,
admin_password, is_first_time, instance_uuid=None,
legacy_bdm_in_spec=True):
...
try:
"""更新数据库"""
updated_instance = driver.instance_update_db(context,
instance_uuid, extra_values=values)
except exception.InstanceNotFound:
LOG.warning(_("Instance disappeared during scheduling"),
context=context, instance_uuid=instance_uuid)
else:
scheduler_utils.populate_filter_properties(filter_properties,
weighed_host.obj)
"""这里self.compute_rpcapi为 nova.compute.rpcapi.ComputeAPI对象"""
self.compute_rpcapi.run_instance(context,
instance=updated_instance,
host=weighed_host.obj.host,
request_spec=request_spec,
filter_properties=filter_properties,
requested_networks=requested_networks,
injected_files=injected_files,
admin_password=admin_password, is_first_time=is_first_time,
node=weighed_host.obj.nodename,
legacy_bdm_in_spec=legacy_bdm_in_spec)
nova/compute/rpcapi.py
ComputeAPI类：
def run_instance(self, ctxt, instance, host, request_spec,
filter_properties, requested_networks,
injected_files, admin_password,
is_first_time, node=None, legacy_bdm_in_spec=True):
instance_p = jsonutils.to_primitive(instance)
msg_kwargs = {'instance': instance_p, 'request_spec': request_spec,
'filter_properties': filter_properties,
'requested_networks': requested_networks,
'injected_files': injected_files,
'admin_password': admin_password,
'is_first_time': is_first_time, 'node': node}
if _icehouse_compat() or self.client.can_send_version('2.37'):
version = _get_version('2.37')
msg_kwargs['legacy_bdm_in_spec'] = legacy_bdm_in_spec
else:
version = '2.19'
cctxt = self.client.prepare(server=host,
version=version)
cctxt.cast(ctxt, 'run_instance', **msg_kwargs)
根据http://www.cnblogs.com/littlebugfish/p/4058007.html中简述的消息队列调用原理，这里将转到nova-compute进程中进行处理。
四、在nova-compute进程中进行处理
nova/compute/manager.py
ComputeManager类：
@wrap_exception()
@reverts_task_state
@wrap_instance_event
@wrap_instance_fault
def run_instance(self, context, instance, request_spec=None,
filter_properties=None, requested_networks=None,
injected_files=None, admin_password=None,
is_first_time=False, node=None, legacy_bdm_in_spec=True):
if filter_properties is None:
filter_properties = {}
@utils.synchronized(instance['uuid'])
def do_run_instance():
self._run_instance(context, request_spec,
filter_properties, requested_networks, injected_files,
admin_password, is_first_time, node, instance,
legacy_bdm_in_spec)
do_run_instance()
def _run_instance(self, context, request_spec,
filter_properties, requested_networks, injected_files,
admin_password, is_first_time, node, instance,
legacy_bdm_in_spec):
...
instance, network_info = self._build_instance(context,
request_spec, filter_properties, requested_networks,
injected_files, admin_password, is_first_time, node,
instance, image_meta, legacy_bdm_in_spec)
notify("end", msg=_("Success"), network_info=network_info)
...
def _build_instance(self, context, request_spec, filter_properties,
requested_networks, injected_files, admin_password, is_first_time,
node, instance, image_meta, legacy_bdm_in_spec):
context = context.elevated()
...
try:
limits = filter_properties.get('limits', {})
with rt.instance_claim(context, instance, limits):
...
instance = self._spawn(context, instance, image_meta,
network_info, block_device_info,
injected_files, admin_password,
set_access_ip=set_access_ip)
...
# spawn success
return instance, network_info
def _spawn(self, context, instance, image_meta, network_info,
block_device_info, injected_files, admin_password,
set_access_ip=False):
"""Spawn an instance with error logging and update its power state."""
instance = self._instance_update(context, instance['uuid'],
vm_state=vm_states.BUILDING,
task_state=task_states.SPAWNING,
expected_task_state=task_states.BLOCK_DEVICE_MAPPING)
try:
self.driver.spawn(context, instance, image_meta,
injected_files, admin_password,
network_info,
block_device_info)
...
return self._instance_update(context, instance['uuid'],
**update_data)
这里将调用相应的Driver对象进行虚拟机的创建，此处以LibvirtDriver类对象为例，后续处理过程可以查看：http://www.cnblogs.com/littlebugfish/p/4058115.html中的分析！