openstack创建instance的流程

http://ezzze.iteye.com/blog/1164920

workflow:




1.用户向nova-api发送请求

用户发送请求到nova-api,这里有两种：
a.通过openstack api
从 server.py's controller.create():

self.helper.create_instance(req,body,self.compute_api.create)

create_instance_helper.CreateInstanceHelper() 查表获取基本信息
b.通过ec2 api
从cloud.py.run_instances()

统一调 computer.api.create() 将新的数据插回去

self._ask_scheduler_to_create_instance(context,base_options,
instance_type,zone_blob,
availability_zone,injected_files,
admin_password,image,
instance_id=instance_id,
requested_networks=requested_networks)

2.API 将处理好的数据通过MQ 转发给scheduler .(code from Computer.api)

rpc.cast(context,
FLAGS.scheduler_topic,
{"method":"run_instance",
"args":{"topic":FLAGS.compute_topic,
"instance_id":instance_id,
"request_spec":request_spec,
"availability_zone":availability_zone,
"admin_password":admin_password,
"injected_files":injected_files,
"requested_networks":requested_networks}})

3.Scheduler 获取信息并作出决定 哪一个host 可以来run instance.

def__getattr__(self,key):
returnfunctools.partial(self._schedule,key)

def_schedule(self,method,context,topic,*args,**kwargs):
.......
rpc.cast(context,
db.queue_get_for(context,topic,host),
{"method":method,
"args":kwargs})
LOG.debug(_("Castedto%(topic)s%(host)sfor%(method)s")%locals())

4.Computer 从池中获取信息 并让 Networker 去准备一个ip ,让volume 准备卷, 然后初始化相应的信息,例如创建image,映射device,创建domain,
并将domain 放入running pool中 然后就进入等待直到instance的状态变为running.

a. networker 分配ip

network_info=self.network_api.allocate_for_instance(context,
instance,vpn=is_vpn,
requested_networks=requested_networks)

defallocate_floating_ip(self,context):
returnrpc.call(context,
FLAGS.network_topic,
{'method':'allocate_floating_ip',
'args':{'project_id':context.project_id}})

b 让 volume 准备卷

bd_mapping=self._setup_block_device_mapping(context,instance_id)
defcreate(self,context,size,snapshot_id,name,description,
volume_type=None,metadata=None,availability_zone=None):
rpc.cast(context,
FLAGS.scheduler_topic,
{"method":"create_volume",
"args":{"topic":FLAGS.volume_topic,
"volume_id":volume['id'],
"snapshot_id":snapshot_id}})

c call nova.virt.libvirt.firewall.IptablesFirewallDriver 建立网络规则
这里是重头戏，单独开个贴记录下....
d call libvirt 创建domian 并launch

domain=self._create_new_domain(xml)
def_create_new_domain(self,xml,persistent=True,launch_flags=0):
ifpersistent:
#Tocreateapersistentdomain,firstdefineit,thenlaunchit.
domain=self._conn.defineXML(xml)
domain.createWithFlags(launch_flags)
else:
#createXMLcallcreatesatransientdomain
domain=self._conn.createXML(xml,launch_flags)
returndomain

e call virt.libvirt.connetion.spwan 等待

defspawn(self,context,instance,network_info,
block_device_info=None):
..........
def_wait_for_boot():
instance_name=instance['name']
try:
state=self.get_info(instance_name)['state']
exceptexception.NotFound:
msg=_("Duringreboot,%sdisappeared.")%instance_name
LOG.error(msg)
raiseutils.LoopingCallDone

ifstate==power_state.RUNNING:
msg=_("Instance%sspawnedsuccessfully.")%instance_name
LOG.info(msg)
raiseutils.LoopingCallDone

timer=utils.LoopingCall(_wait_for_boot)
returntimer.start(interval=0.5,now=True)

5一旦instance的状态改变至running,他就会去通过networker获取网络信息, 这里有几种方式,取决于你的networkManager