Openstack Nova 源码分析 — RPC 远程调用过程

目录

Nova Project Services

Project 的程序入口( setup.py )

console_scripts =

nova-api = nova.cmd.api:main

console_scripts

console_scripts =
nova-all = nova.cmd.all:main                          #启动所有Nova服务的辅助脚本
nova-api = nova.cmd.api:main                          #作为WSGI服务器对外提供Restful API服务，有三种类型nova-api-ec2/，通过nova.conf中的enable_apis选项值来决定。
nova-api-ec2 = nova.cmd.api_ec2:main                  #EC2 API支持
nova-api-metadata = nova.cmd.api_metadata:main
nova-api-os-compute = nova.cmd.api_os_compute:main    #Openstack API服务
nova-cells = nova.cmd.cells:main
nova-cert = nova.cmd.cert:main                        #管理X509证书
nova-compute = nova.cmd.compute:main                  #compute服务，负责虚拟机的生命周期管理
nova-conductor = nova.cmd.conductor:main              #conductor服务，负责与数据库的交互
nova-console = nova.cmd.console:main
nova-consoleauth = nova.cmd.consoleauth:main
nova-dhcpbridge = nova.cmd.dhcpbridge:main            #管理nova-network的DHCP bridge
nova-idmapshift = nova.cmd.idmapshift:main
nova-manage = nova.cmd.manage:main
nova-network = nova.cmd.network:main                  #已经被Neutron取代，只有在使用Devstack部署的时候才会被使用
nova-novncproxy = nova.cmd.novncproxy:main            #支持用户通过该代理服务以vnc连接到虚拟机实例
nova-objectstore = nova.cmd.objectstore:main          #兼容EC2的存储接口
nova-rootwrap = oslo_rootwrap.cmd:main                #在Openstack运行的过程中，支持以root的身份来运行某些shell指令
nova-rootwrap-daemon = oslo_rootwrap.cmd:daemon
nova-scheduler = nova.cmd.scheduler:main              #scheduler服务，服务计算节点物理资源的调度
nova-serialproxy = nova.cmd.serialproxy:main
nova-spicehtml5proxy = nova.cmd.spicehtml5proxy:main
nova-xvpvncproxy = nova.cmd.xvpvncproxy:main          #允许用户通过代理的方式来访问虚拟机实例的控制台。

nova.api.v21.extensions

nova.api.v21.extensions

Nova中RPC(远程过程调用)

nova-compute RPC API的实现

# nova/nova/compute/rpcapi.py
class ComputeAPI(object):

# 这是一个RPC远程调用的方法
def live_migration(self, ctxt, instance, dest, block_migration, host,
migration, migrate_data=None):
args = {'migration': migration}
version = '4.2'
if not self.client.can_send_version(version):
version = '4.0'

# 获取目标 compute 主机(DEST HOST)的RPC client，即被调用的服务进程的HostIP
cctxt = self.client.prepare(server=host, version=version)

# 通过目标主机对象的 RPC cliient 来调用远程过程方法 cast() ，以此来实现远程调用
cctxt.cast(ctxt, 'live_migration', instance=instance,
dest=dest, block_migration=block_migration,
migrate_data=migrate_data, **args)
# cast()异步远程调用，不会阻塞别的进程，适合于需要长时间进行的执行过程
# cast()的第二个参数是RPC client调用的函数名，case()后面的参数会继续作为参数传入该调用函数
# cast()函数内的live_migration()函数是 manager.live_migration() 视具体实现迁移功能的函数，在manager.py内实现。

#nova/nova/conductor/tasks/live_migrate.py

class LiveMigrationTask(base.TaskBase):
def __init__(self, context, instance, destination,
block_migration, disk_over_commit, migration, compute_rpcapi,
servicegroup_api, scheduler_client):
super(LiveMigrationTask, self).__init__(context, instance)
...

def _execute(self):
self._check_instance_is_active()
self._check_host_is_up(self.source)

if not self.destination:
self.destination = self._find_destination()
self.migration.dest_compute = self.destination
self.migration.save()
else:
self._check_requested_destination()

# TODO(johngarbutt) need to move complexity out of compute manager
# TODO(johngarbutt) disk_over_commit?

#调用 ComputeAPI 类中的 live_migration() RPC接口，以RPC的方式发出一个请求到Queue再被nova-compute接收
return self.compute_rpcapi.live_migration(self.context,
host=self.source,
instance=self.instance,
dest=self.destination,
block_migration=self.block_migration,
migration=self.migration,
migrate_data=self.migrate_data)

nova.compute.manager 模块

# nova/nova/compute/manager.py

5189     def live_migration(self, context, dest, instance, block_migration,
1                        migration, migrate_data):
2         """Executing live migration.
3
4         :param context: security context
5         :param dest: destination host
6         :param instance: a nova.objects.instance.Instance object
7         :param block_migration: if true, prepare for block migration
8         :param migration: an nova.objects.Migration object
9         :param migrate_data: implementation specific params
10
11         """
12
13         # NOTE(danms): Remove these guards in v5.0 of the RPC API
14         if migration:
15             migration.status = 'queued'
16             migration.save()
17
18         def dispatch_live_migration(*args, **kwargs):
19             with self._live_migration_semaphore:
20                 self._do_live_migration(*args, **kwargs)
21
22         # NOTE(danms): We spawn here to return the RPC worker thread back to
23         # the pool. Since what follows could take a really long time, we don't
24         # want to tie up RPC workers.
25         utils.spawn_n(dispatch_live_migration,
26                       context, dest, instance,
27                       block_migration, migration,
28                       migrate_data)

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