1. nova-api接收到request

在/etc/nova/api-paste.ini中，是这样配置nova v2的

[app:osapi_compute_app_v2]
paste.app_factory = nova.api.openstack.compute:APIRouter.factory

在/usr/lib/python2.7/dist-packages/nova/api/openstack/compute/__init__.py中

class APIRouter(nova.api.openstack.APIRouter):中的

from nova.api.openstack.compute import servers
def _setup_routes(self, mapper, ext_mgr, init_only):
    ……
    self.resources['servers'] = servers.create_resource(ext_mgr)
    mapper.resource("server", "servers",
                controller=self.resources['servers'],
                collection={'detail': 'GET'},
                member={'action': 'POST'})

……

对于发送给/servers的POST的请求，是发给controller的。

在/usr/lib/python2.7/dist-packages/nova/api/openstack/compute/servers.py中有下面的函数

def create_resource(ext_mgr):
return wsgi.Resource(Controller(ext_mgr))

class Controller(wsgi.Controller):
    @wsgi.response(202)
    @wsgi.serializers(xml=FullServerTemplate)
    @wsgi.deserializers(xml=CreateDeserializer)
    def create(self, req, body):
        ……

接收到的request的格式如下：

{"server": {"name": "world", "imageRef": "6a1489cb-5905-4f97-ae8b-012770818213", "availability_zone": "nova", "key_name": "153key", "flavorRef": "2", "OS-DCF:diskConfig": "AUTO", "max_count": 1, "min_count": 1, "networks": [{"uuid": "a29561e9-2f32-4765-a0f8-306b870f780b"}], "security_groups": [{"name": "default"}]}}

然后开始解析这个request，得到

password: 如果request中有的解析出，没有则随机generate一个
name
image_uuid
personality：从中得到config_drive或者injected_files
security_groups
requested_networks
flavor_id
key_name
user_data
availability_zone
block_device_mapping
min_count
max_count
auto_disk_config：是否自动配置硬盘到flavor指定的大小，OS-DCF，auto_disk_config
scheduler_hints：为scheduler提供参数

最终调用

(instances, resv_id) = self.compute_api.create(context,
                inst_type,
                image_uuid,
                display_name=name,
                display_description=name,
                key_name=key_name,
                metadata=server_dict.get('metadata', {}),
                access_ip_v4=access_ip_v4,
                access_ip_v6=access_ip_v6,
                injected_files=injected_files,
                admin_password=password,
                min_count=min_count,
                max_count=max_count,
                requested_networks=requested_networks,
                security_group=sg_names,
                user_data=user_data,
                availability_zone=availability_zone,
                config_drive=config_drive,
                block_device_mapping=block_device_mapping,
                auto_disk_config=auto_disk_config,
                scheduler_hints=scheduler_hints,
                legacy_bdm=legacy_bdm)

这一调用调用到/usr/lib/python2.7/dist-packages/nova/compute/api.py中

class API(base.Base):

@hooks.add_hook("create_instance")
    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, 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):
         ……
         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,
                       scheduler_hints=scheduler_hints,
                       legacy_bdm=legacy_bdm)

API的_create_instance的函数

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_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):

_check_and_transform_bdm
_provision_instances：在数据库中创建instance对象create_db_entry_for_new_instance，将状态设为vm_states.BUILDING
_build_filter_properties：从scheduler_hints中得到filter_properties['instance_type']，filter_properties['force_hosts']，filter_properties['force_nodes']
_update_instance_group：从scheduler_hints得到'group'，将instance加入group
_record_action_start:instance_actions.CREATE
self.compute_task_api.build_instances：调用conductor.ComputeTaskAPI()

/usr/lib/python2.7/dist-packages/nova/conductor/api.py中

class ComputeTaskAPI(object):
    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)

conductor_compute_rpcapi指向nova.conductor.rpcapi.ComputeTaskAPI()

def build_instances(self, context, instances, image, filter_properties,
        admin_password, injected_files, requested_networks,
        security_groups, block_device_mapping, legacy_bdm=True):
    image_p = jsonutils.to_primitive(image)
    cctxt = self.client.prepare(version='1.5')
    cctxt.cast(context, 'build_instances',
               instances=instances, 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)

这是一个RPC调用，最终能够调用到/usr/lib/python2.7/dist-packages/nova/conductor/manager.py的class ConductorManager(manager.Manager)

2. nova-conductor

def build_instances(self, context, instances, image, filter_properties,
        admin_password, injected_files, requested_networks,
        security_groups, block_device_mapping, legacy_bdm=True):
    request_spec = scheduler_utils.build_request_spec(context, image,
                                                      instances)
    # NOTE(alaski): For compatibility until a new scheduler method is used.
    request_spec.update({'block_device_mapping': block_device_mapping,
                         'security_group': security_groups})
    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)

它调用/usr/lib/python2.7/dist-packages/nova/scheduler/rpcapi.py中class SchedulerAPI(object):

def run_instance(self, ctxt, request_spec, admin_password,
        injected_files, requested_networks, is_first_time,
        filter_properties, legacy_bdm_in_spec=True):
    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,
                  'legacy_bdm_in_spec': legacy_bdm_in_spec}
    cctxt = self.client.prepare()
    cctxt.cast(ctxt, 'run_instance', **msg_kwargs)

这是一个RPC调用，最终调用到/usr/lib/python2.7/dist-packages/nova/scheduler/manager.py的class SchedulerManager(manager.Manager):

3. nova-scheduler

def run_instance(self, context, request_spec, admin_password,
        injected_files, requested_networks, is_first_time,
        filter_properties, legacy_bdm_in_spec=True):
    return self.driver.schedule_run_instance(context,
        request_spec, admin_password, injected_files,
        requested_networks, is_first_time, filter_properties,
        legacy_bdm_in_spec)

scheduler的driver我们在nova.conf中配置如下：

#scheduler
compute_scheduler_driver=nova.scheduler.filter_scheduler.FilterScheduler

/usr/lib/python2.7/dist-packages/nova/scheduler/filter_scheduler.py的class FilterScheduler(driver.Scheduler):

def schedule_run_instance(self, context, request_spec,
                          admin_password, injected_files,
                          requested_networks, is_first_time,
                          filter_properties, legacy_bdm_in_spec):

instance_uuids = request_spec.get('instance_uuids')所有instance的id
weighed_hosts = self._schedule(context, request_spec, filter_properties, instance_uuids)
for num, instance_uuid in enumerate(instance_uuids):
- weighed_host = weighed_hosts.pop(0)
- 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)

_provision_resource调用

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)

调用/usr/lib/python2.7/dist-packages/nova/compute/rpcapi.py的class ComputeAPI(object):

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):
    # NOTE(russellb) Havana compat
    version = self._get_compat_version('3.0', '2.37')
    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,
                  'legacy_bdm_in_spec': legacy_bdm_in_spec}

cctxt = self.client.prepare(server=host, version=version)
cctxt.cast(ctxt, 'run_instance', **msg_kwargs)

这是一个RPC调用，最终调用/usr/lib/python2.7/dist-packages/nova/compute/manager.py的class ComputeManager(manager.Manager)

4. nova-compute

def run_instance(self, context, instance, request_spec,
                 filter_properties, requested_networks,
                 injected_files, admin_password,
                 is_first_time, node, legacy_bdm_in_spec):
    self._run_instance(context, request_spec,
        filter_properties, requested_networks, injected_files,
        admin_password, is_first_time, node, instance,
        legacy_bdm_in_spec)

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)

security_groups = request_spec.get('security_group')
node = self.driver.get_available_nodes(refresh=True)[0]
bdms = block_device_obj.BlockDeviceMappingList.get_by_instance_uuid(context, instance['uuid'])
injected_files = self._decode_files(injected_files)
rt = self._get_resource_tracker(node)
with rt.instance_claim(context, instance, limits):
- macs = self.driver.macs_for_instance(instance)
- dhcp_options = self.driver.dhcp_options_for_instance(instance)
- network_info = self._allocate_network(context, instance,
  requested_networks, macs, security_groups,
  dhcp_options)
- self._instance_update(
                          context, instance['uuid'],
                          vm_state=vm_states.BUILDING,
                          task_state=task_states.BLOCK_DEVICE_MAPPING)
- self._default_block_device_names(context, instance, image_meta, bdms)
- block_device_info = self._prep_block_device(context, instance, bdms)
- instance = self._spawn(context, instance, image_meta,
                                         network_info, block_device_info,
                                         injected_files, admin_password,
                                         set_access_ip=set_access_ip)

4.1. 配置network

_allocate_network中，状态变成Networking

instance = self._instance_update(context, instance['uuid'],
                                 vm_state=vm_states.BUILDING,
                                 task_state=task_states.NETWORKING,
                                 expected_task_state=[None])

return nova.network.model.NetworkInfoAsyncWrapper(
        self._allocate_network_async, context, instance,
        requested_networks, macs, security_groups, is_vpn,
        dhcp_options)

def _allocate_network_async(self, context, instance, requested_networks,
                            macs, security_groups, is_vpn, dhcp_options):
    nwinfo = self.network_api.allocate_for_instance(
        context, instance, vpn=is_vpn,
        requested_networks=requested_networks,
        macs=macs,
        security_groups=security_groups,
        dhcp_options=dhcp_options)

调用network_api，调用neutron来创建network，nova.network.neutronv2.api.API

调用/usr/lib/python2.7/dist-packages/nova/network/neutronv2/api.py的allocate_for_instance函数

neutron = neutronv2.get_client(context)
nets = self._get_available_networks(context, instance['project_id'], net_ids)
- (Pdb) p nets
  [{u'status': u'ACTIVE', u'subnets': [u'bd652c3e-005e-4985-b65e-576c3045e890'], u'name': u'openstack-net', u'admin_state_up': True, u'tenant_id': u'8efa4856fe4b4aa0b6dcf05dc66d4efa', u'router:external': False, u'shared': False, u'id': u'a29561e9-2f32-4765-a0f8-306b870f780b'}]
user_security_groups = neutron.list_security_groups(**search_opts).get('security_groups')
- (Pdb) p security_groups
  [u'default']
self._populate_neutron_extension_values(context, instance, port_req_body)
- (Pdb) p port_req_body
  {'port': {'device_owner': u'compute:nova', 'device_id': u'3a5cd5d4-2676-447b-bab4-6acf21feacd6'}}
- RESP:{'status': '200', 'content-length': '3703', 'content-location': 'http://127.0.0.1:9696/v2.0/extensions.json', 'date': 'Mon, 02 Jun 2014 20:52:37 GMT', 'content-type': 'application/json; charset=UTF-8', 'x-openstack-request-id': 'req-518cd143-e3a5-4f5d-a71b-32b19d69bf2a'} {"extensions": [{"updated": "2012-10-05T10:00:00-00:00", "name": "security-group", "links": [], "namespace": "http://docs.openstack.org/ext/securitygroups/api/v2.0", "alias": "security-group", "description": "The security groups extension."}, {"updated": "2013-02-07T10:00:00-00:00", "name": "L3 Agent Scheduler", "links": [], "namespace": "http://docs.openstack.org/ext/l3_agent_scheduler/api/v1.0", "alias": "l3_agent_scheduler", "description": "Schedule routers among l3 agents"}, {"updated": "2013-03-28T10:00:00-00:00", "name": "Neutron L3 Configurable external gateway mode", "links": [], "namespace": "http://docs.openstack.org/ext/neutron/ext-gw-mode/api/v1.0", "alias": "ext-gw-mode", "description": "Extension of the router abstraction for specifying whether SNAT should occur on the external gateway"}, {"updated": "2014-02-03T10:00:00-00:00", "name": "Port Binding", "links": [], "namespace": "http://docs.openstack.org/ext/binding/api/v1.0", "alias": "binding", "description": "Expose port bindings of a virtual port to external application"}, {"updated": "2012-09-07T10:00:00-00:00", "name": "Provider Network", "links": [], "namespace": "http://docs.openstack.org/ext/provider/api/v1.0", "alias": "provider", "description": "Expose mapping of virtual networks to physical networks"}, {"updated": "2013-02-03T10:00:00-00:00", "name": "agent", "links": [], "namespace": "http://docs.openstack.org/ext/agent/api/v2.0", "alias": "agent", "description": "The agent management extension."}, {"updated": "2012-07-29T10:00:00-00:00", "name": "Quota management support", "links": [], "namespace": "http://docs.openstack.org/network/ext/quotas-sets/api/v2.0", "alias": "quotas", "description": "Expose functions for quotas management per tenant"}, {"updated": "2013-02-07T10:00:00-00:00", "name": "DHCP Agent Scheduler", "links": [], "namespace": "http://docs.openstack.org/ext/dhcp_agent_scheduler/api/v1.0", "alias": "dhcp_agent_scheduler", "description": "Schedule networks among dhcp agents"}, {"updated": "2013-06-27T10:00:00-00:00", "name": "Multi Provider Network", "links": [], "namespace": "http://docs.openstack.org/ext/multi-provider/api/v1.0", "alias": "multi-provider", "description": "Expose mapping of virtual networks to multiple physical networks"}, {"updated": "2013-01-14T10:00:00-00:00", "name": "Neutron external network", "links": [], "namespace": "http://docs.openstack.org/ext/neutron/external_net/api/v1.0", "alias": "external-net", "description": "Adds external network attribute to network resource."}, {"updated": "2012-07-20T10:00:00-00:00", "name": "Neutron L3 Router", "links": [], "namespace": "http://docs.openstack.org/ext/neutron/router/api/v1.0", "alias": "router", "description": "Router abstraction for basic L3 forwarding between L2 Neutron networks and access to external networks via a NAT gateway."}, {"updated": "2013-07-23T10:00:00-00:00", "name": "Allowed Address Pairs", "links": [], "namespace": "http://docs.openstack.org/ext/allowedaddresspairs/api/v2.0", "alias": "allowed-address-pairs", "description": "Provides allowed address pairs"}, {"updated": "2013-03-17T12:00:00-00:00", "name": "Neutron Extra DHCP opts", "links": [], "namespace": "http://docs.openstack.org/ext/neutron/extra_dhcp_opt/api/v1.0", "alias": "extra_dhcp_opt", "description": "Extra options configuration for DHCP. For example PXE boot options to DHCP clients can be specified (e.g. tftp-server, server-ip-address, bootfile-name)"}, {"updated": "2013-02-01T10:00:00-00:00", "name": "Neutron Extra Route", "links": [], "namespace": "http://docs.openstack.org/ext/neutron/extraroutes/api/v1.0", "alias": "extraroute", "description": "Extra routes configuration for L3 router"}]}
created_port = self._create_port(port_client, instance, network_id, port_req_body, fixed_ips.get(network_id),security_group_ids, available_macs, dhcp_opts)
- (Pdb) p port_req_body
  {'port': {'binding:host_id': u'OpenstackIcehouse2', 'admin_state_up': True, 'network_id': u'a29561e9-2f32-4765-a0f8-306b870f780b', 'tenant_id': u'8efa4856fe4b4aa0b6dcf05dc66d4efa', 'device_owner': u'compute:nova', 'security_groups': [u'b4a79ec8-8552-4074-a410-faa52b30424d'], 'device_id': u'3a5cd5d4-2676-447b-bab4-6acf21feacd6'}}
- RESP:{'date': 'Mon, 02 Jun 2014 20:56:01 GMT', 'status': '201', 'content-length': '717', 'content-type': 'application/json; charset=UTF-8', 'x-openstack-request-id': 'req-a9ef458b-adfe-41f9-b66a-640cb8d56833'} {"port": {"status": "DOWN", "binding:host_id": "OpenstackIcehouse2", "name": "", "allowed_address_pairs": [], "admin_state_up": true, "network_id": "a29561e9-2f32-4765-a0f8-306b870f780b", "tenant_id": "8efa4856fe4b4aa0b6dcf05dc66d4efa", "binding:vif_details": {"port_filter": true, "ovs_hybrid_plug": true}, "binding:vnic_type": "normal", "binding:vif_type": "ovs", "device_owner": "compute:nova", "mac_address": "fa:16:3e:64:b6:8a", "binding:profile": {}, "fixed_ips": [{"subnet_id": "bd652c3e-005e-4985-b65e-576c3045e890", "ip_address": "192.168.2.19"}], "id": "9d6cd91a-dac8-4523-a692-01dc61c04b21", "security_groups": ["b4a79ec8-8552-4074-a410-faa52b30424d"], "device_id": "3a5cd5d4-2676-447b-bab4-6acf21feacd6"}}
nw_info = self.get_instance_nw_info(context, instance, networks=nets, port_ids=ports_in_requested_order)
- (Pdb) p nw_info
  [VIF({'ovs_interfaceid': u'9d6cd91a-dac8-4523-a692-01dc61c04b21', 'network': Network({'bridge': 'br-int', 'subnets': [Subnet({'ips': [FixedIP({'meta': {}, 'version': 4, 'type': 'fixed', 'floating_ips': [], 'address': u'192.168.2.19'})], 'version': 4, 'meta': {'dhcp_server': u'192.168.2.2'}, 'dns': [IP({'meta': {}, 'version': 4, 'type': 'dns', 'address': u'8.8.8.8'})], 'routes': [], 'cidr': u'192.168.2.0/24', 'gateway': IP({'meta': {}, 'version': 4, 'type': 'gateway', 'address': u'192.168.2.1'})})], 'meta': {'injected': False, 'tenant_id': u'8efa4856fe4b4aa0b6dcf05dc66d4efa'}, 'id': u'a29561e9-2f32-4765-a0f8-306b870f780b', 'label': u'openstack-net'}), 'devname': u'tap9d6cd91a-da', 'qbh_params': None, 'meta': {}, 'details': {u'port_filter': True, u'ovs_hybrid_plug': True}, 'address': u'fa:16:3e:64:b6:8a', 'active': False, 'type': u'ovs', 'id': u'9d6cd91a-dac8-4523-a692-01dc61c04b21', 'qbg_params': None})]

4.2. _spawn instances

/usr/lib/python2.7/dist-packages/nova/compute/manager.py的

def _spawn(self, context, instance, image_meta, network_info,
           block_device_info, injected_files, admin_password,
           set_access_ip=False):
    self.driver.spawn(context, instance, image_meta,
                  injected_files, admin_password,
                  network_info,
                  block_device_info)

在nova.conf中compute_driver=libvirt.LibvirtDriver

所以会最终调用/usr/lib/python2.7/dist-packages/nova/virt/libvirt/driver.py

5. libvirt

/usr/lib/python2.7/dist-packages/nova/virt/libvirt/driver.py的class LibvirtDriver(driver.ComputeDriver):

def spawn(self, context, instance, image_meta, injected_files,
admin_password, network_info=None, block_device_info=None):

disk_info = blockinfo.get_disk_info(CONF.libvirt.virt_type, instance, block_device_info, image_meta)
- (Pdb) p disk_info
  {'disk_bus': 'virtio', 'cdrom_bus': 'ide', 'mapping': {'disk': {'bus': 'virtio', 'boot_index': '1', 'type': 'disk', 'dev': 'vda'}, 'root': {'bus': 'virtio', 'boot_index': '1', 'type': 'disk', 'dev': 'vda'}}}
self._create_image(context, instance,
                   disk_info['mapping'],
                   network_info=network_info,
                   block_device_info=block_device_info,
                   files=injected_files,
                   admin_pass=admin_password)
xml = self.to_xml(context, instance, network_info,
                  disk_info, image_meta,
                  block_device_info=block_device_info,
                  write_to_disk=True)
self._create_domain_and_network(context, xml, instance, network_info,
block_device_info)

5.1. 获取Image

/usr/lib/python2.7/dist-packages/nova/virt/libvirt/driver.py的

def _create_image(self, context, instance,
                  disk_mapping, suffix='',
                  disk_images=None, network_info=None,
                  block_device_info=None, files=None,
                  admin_pass=None, inject_files=True):

在这个函数中参数

(Pdb) p disk_images
{'kernel_id': u'', 'image_id': u'6a1489cb-5905-4f97-ae8b-012770818213', 'ramdisk_id': u''}

得到flavor

inst_type = flavors.extract_flavor(instance)

(Pdb) p inst_type
{'root_gb': 20, 'name': 'm1.small', 'ephemeral_gb': 0, 'memory_mb': 2048, 'vcpus': 1, 'swap': 0, 'rxtx_factor': 1.0, 'flavorid': '2', 'vcpu_weight': None, 'id': 5}

下载和缓存image

image('disk').cache(fetch_func=libvirt_utils.fetch_image,
                    context=context,
                    filename=root_fname,
                    size=size,
                    image_id=disk_images['image_id'],
                    user_id=instance['user_id'],
                    project_id=instance['project_id'])

首先会调用/usr/lib/python2.7/dist-packages/nova/virt/libvirt/utils.py的fetch_image
- images.fetch_to_raw(context, image_id, target, user_id, project_id, max_size=max_size)
- 会调用/usr/lib/python2.7/dist-packages/nova/virt/images.py的fetch_to_raw，最终调用image_service.download(context, image_id, dst_path=path)，会从glance下载下来image
其次，会调用/usr/lib/python2.7/dist-packages/nova/virt/libvirt/imagebackend.py的cache函数
- (Pdb) p base
  '/var/lib/nova/instances/_base/4b1ad1f3fa1222ea960f8e373baa4eef880c5ff1'
- (Pdb) p size
  21474836480
- 会调用class Qcow2(Image)的create_image(self, prepare_template, base, size, *args, **kwargs)并最后调用到copy_qcow2_image
- copy_qcow2_image是调用了两个命令：
  - ('qemu-img', 'create', '-f', 'qcow2', '-o', 'backing_file=/var/lib/nova/instances/_base/4b1ad1f3fa1222ea960f8e373baa4eef880c5ff1', '/var/lib/nova/instances/4d169b6a-b921-4e24-83b0-2c36ea4da7d0/disk')
  - ('qemu-img', 'resize', '/var/lib/nova/instances/4d169b6a-b921-4e24-83b0-2c36ea4da7d0/disk', 21474836480)

配置configuration drive

inst_md = instance_metadata.InstanceMetadata(instance, content=files, extra_md=extra_md, network_info=network_info)

with configdrive.ConfigDriveBuilder(instance_md=inst_md) as cdb:
configdrive_path = self._get_disk_config_path(instance)
cdb.make_drive(configdrive_path)

配置injection file

self._inject_data(instance, network_info, admin_pass, files, suffix)

5.2. 生成XML

to_xml xml=<domain type="kvm">
<uuid>33985948-f19d-4d01-be63-989f302c218e</uuid>
<name>instance-0000001a</name>
<memory>2097152</memory>
<vcpu>1</vcpu>
<sysinfo type="smbios">
    <system>
      <entry name="manufacturer">OpenStack Foundation</entry>
      <entry name="product">OpenStack Nova</entry>
      <entry name="version">2014.1</entry>
      <entry name="serial">21172311-7f0c-44b5-b57c-48e5cc032d12</entry>
      <entry name="uuid">33985948-f19d-4d01-be63-989f302c218e</entry>
    </system>
</sysinfo>
<os>
    <type>hvm</type>
    <boot dev="hd"/>
    <smbios mode="sysinfo"/>
</os>
<features>
    <acpi/>
    <apic/>
</features>
<clock offset="utc">
    <timer name="pit" tickpolicy="delay"/>
    <timer name="rtc" tickpolicy="catchup"/>
    <timer name="hpet" present="no"/>
</clock>
<cpu mode="host-model" match="exact"/>
<devices>
    <disk type="file" device="disk">
      <driver name="qemu" type="qcow2" cache="none"/>
      <source file="/var/lib/nova/instances/33985948-f19d-4d01-be63-989f302c218e/disk"/>
      <target bus="virtio" dev="vda"/>
    </disk>
    <interface type="bridge">
      <mac address="fa:16:3e:f0:c0:b4"/>
      <model type="virtio"/>
      <source bridge="qbr4700fff8-b4"/>
      <target dev="tap4700fff8-b4"/>
    </interface>
    <serial type="file">
      <source path="/var/lib/nova/instances/33985948-f19d-4d01-be63-989f302c218e/console.log"/>
    </serial>
    <serial type="pty"/>
    <input type="tablet" bus="usb"/>
    <graphics type="vnc" autoport="yes" keymap="en-us" listen="0.0.0.0"/>
    <video>
      <model type="cirrus"/>
    </video>
</devices>
</domain>

5.3.创建Instance，并连接到network

/usr/lib/python2.7/dist-packages/nova/virt/libvirt/driver.py的

def _create_domain_and_network(self, context, xml, instance, network_info,
block_device_info=None, power_on=True,
reboot=False, vifs_already_plugged=False):

self.plug_vifs(instance, network_info)
self.firewall_driver.setup_basic_filtering(instance, network_info)
self.firewall_driver.prepare_instance_filter(instance, network_info)
domain = self._create_domain(xml, instance=instance, launch_flags=launch_flags, power_on=power_on)

首先是调用/usr/lib/python2.7/dist-packages/nova/virt/libvirt/vif.py的def plug_ovs_hybrid(self, instance, vif):

iface_id = self.get_ovs_interfaceid(vif)
- (Pdb) p iface_id
  u'4700fff8-b437-45fb-8b81-dbd69dec2b5a'
br_name = self.get_br_name(vif['id'])
- (Pdb) p br_name
  u'qbr4700fff8-b4'
v1_name, v2_name = self.get_veth_pair_names(vif['id'])
- (Pdb) p v1_name
  u'qvb4700fff8-b4'
- (Pdb) p v2_name
  u'qvo4700fff8-b4'
utils.execute('brctl', 'addbr', br_name, run_as_root=True)
utils.execute('brctl', 'setfd', br_name, 0, run_as_root=True)
utils.execute('brctl', 'stp', br_name, 'off', run_as_root=True)
utils.execute('tee', ('/sys/class/net/%s/bridge/multicast_snooping' % br_name), process_input='0', run_as_root=True, check_exit_code=[0, 1])
linux_net._create_veth_pair(v1_name, v2_name)
utils.execute('ip', 'link', 'set', br_name, 'up', run_as_root=True)
utils.execute('brctl', 'addif', br_name, v1_name, run_as_root=True)
linux_net.create_ovs_vif_port(self.get_bridge_name(vif), v2_name, iface_id, vif['address'], instance['uuid'])
- (Pdb) p vif
  VIF({'ovs_interfaceid': u'4700fff8-b437-45fb-8b81-dbd69dec2b5a', 'network': Network({'bridge': 'br-int', 'subnets': [Subnet({'ips': [FixedIP({'meta': {}, 'version': 4, 'type': 'fixed', 'floating_ips': [], 'address': u'192.168.2.18'})], 'version': 4, 'meta': {'dhcp_server': u'192.168.2.2'}, 'dns': [IP({'meta': {}, 'version': 4, 'type': 'dns', 'address': u'8.8.8.8'})], 'routes': [], 'cidr': u'192.168.2.0/24', 'gateway': IP({'meta': {}, 'version': 4, 'type': 'gateway', 'address': u'192.168.2.1'})})], 'meta': {'injected': False, 'tenant_id': u'8efa4856fe4b4aa0b6dcf05dc66d4efa'}, 'id': u'a29561e9-2f32-4765-a0f8-306b870f780b', 'label': u'openstack-net'}), 'devname': u'tap4700fff8-b4', 'qbh_params': None, 'meta': {}, 'details': {u'port_filter': True, u'ovs_hybrid_plug': True}, 'address': u'fa:16:3e:f0:c0:b4', 'active': False, 'type': u'ovs', 'id': u'4700fff8-b437-45fb-8b81-dbd69dec2b5a', 'qbg_params': None})
- _ovs_vsctl(['--', '--if-exists', 'del-port', dev, '--',
                  'add-port', bridge, dev,
                  '--', 'set', 'Interface', dev,
                  'external-ids:iface-id=%s' % iface_id,
                  'external-ids:iface-status=active',
                  'external-ids:attached-mac=%s' % mac,
                  'external-ids:vm-uuid=%s' % instance_id])
- _set_device_mtu(dev)

其次调用/usr/lib/python2.7/dist-packages/nova/virt/libvirt/driver.py的

def _create_domain(self, xml=None, domain=None,
instance=None, launch_flags=0, power_on=True):

domain = self._conn.defineXML(xml)
domain.createWithFlags(launch_flags)

机器运行起来了。

秒客网

Icehouse 创建Instance代码分析