import sysfrom nova.cmd.api import mainif __name__ == "__main__":　　sys.exit(main())

def main():    config.parse_args(sys.argv)    logging.setup("nova")    utils.monkey_patch()    launcher = service.process_launcher()    for api in CONF.enabled_apis:        should_use_ssl = api in CONF.enabled_ssl_apis        if api == ‘ec2‘:            """为了与ec2兼容"""            server = service.WSGIService(api, use_ssl=should_use_ssl,                                         max_url_len=16384)         else:            server = service.WSGIService(api, use_ssl=should_use_ssl) 【1】        launcher.launch_service(server, workers=server.workers or 1)【2】    """当前进程处于等待状态"""　　launcher.wait()

WSGIService类：def __init__(self, name, loader=None, use_ssl=False, max_url_len=None):    self.name = name    self.manager = self._get_manager()    self.loader = loader or wsgi.Loader()    self.app = self.loader.load_app(name)    self.host = getattr(CONF, ‘%s_listen‘ % name, "0.0.0.0")    self.port = getattr(CONF, ‘%s_listen_port‘ % name, 0)    self.workers = getattr(CONF, ‘%s_workers‘ % name, None)    self.use_ssl = use_ssl    """封装了wsgi.py中的server"""    self.server = wsgi.Server(name,                              self.app,                              host=self.host,                              port=self.port,                              use_ssl=self.use_ssl,                              max_url_len=max_url_len)    # Pull back actual port used    self.port = self.server.port    self.backdoor_port = None

Loader类：def __init__(self, config_path=None):　　"""试图寻找api-paste.ini配置文件"""　　self.config_path = None　　config_path = config_path or CONF.api_paste_config　　if not os.path.isabs(config_path):　　　　self.config_path = CONF.find_file(config_path)　　elif os.path.exists(config_path):　　　　self.config_path = config_path　　if not self.config_path:　　　　raise exception.ConfigNotFound(path=config_path)def load_app(self, name):　　try:　　　　LOG.debug("Loading app %(name)s from %(path)s",                {‘name‘: name, ‘path‘: self.config_path})　　　　return deploy.loadapp("config:%s" % self.config_path, name=name)　　except LookupError as err:　　　　LOG.error(err)　　　　raise exception.PasteAppNotFound(name=name, path=self.config_path)    

ProcessLauncher类：def launch_service(self, service, workers=1):　　wrap = ServiceWrapper(service, workers)　　LOG.info(_(‘Starting %d workers‘), wrap.workers)　　"""循环启动workers数目的子进程"""　　while self.running and len(wrap.children) < wrap.workers:　　　　self._start_child(wrap)def _start_child(self, wrap):　　...　　"""创建子进程"""　　pid = os.fork()　　if pid == 0:            　　　　status = 0　　　　try:　　　　　　"""子进程进行处理"""　　　　　　self._child_process(wrap.service)　　　　except SignalExit as exc:　　　　　　signame = {signal.SIGTERM: ‘SIGTERM‘,                    signal.SIGINT: ‘SIGINT‘}[exc.signo]　　　　　　LOG.info(_(‘Caught %s, exiting‘), signame)　　　　　　status = exc.code　　　　except SystemExit as exc:　　　　　　status = exc.code　　　　except BaseException:　　　　　　LOG.exception(_(‘Unhandled exception‘))　　　　　　status = 2　　　　finally:　　　　　　"""出现异常停掉服务"""　　　　　　wrap.service.stop()　　　　"""子进程退出"""　　　　os._exit(status)　　LOG.info(_(‘Started child %d‘), pid)　　wrap.children.add(pid)　　self.children[pid] = wrap　　return piddef _child_process(self, service):　　...　　launcher = Launcher()　　launcher.run_service(service)

Launcher类：def __init__(self):    self._services = threadgroup.ThreadGroup()    self.backdoor_port = eventlet_backdoor.initialize_if_enabled() @staticmethoddef run_service(service):    service.start()    service.wait()

WSGIService类：def start(self):
    if self.manager:        self.manager.init_host()        self.manager.pre_start_hook()        if self.backdoor_port is not None:            self.manager.backdoor_port = self.backdoor_port    self.server.start()    if self.manager:        self.manager.post_start_hook()def wait(self):    self.server.wait()

Server类：def start(self):    ...    wsgi_kwargs = {        ‘func‘: eventlet.wsgi.server,        ‘sock‘: self._socket,        ‘site‘: self.app,        ‘protocol‘: self._protocol,        ‘custom_pool‘: self._pool,        ‘log‘: self._wsgi_logger,        ‘log_format‘: CONF.wsgi_log_format        }    if self._max_url_len:        wsgi_kwargs[‘url_length_limit‘] = self._max_url_len    """创建一个green thread，运行func函数，在其中传入后面的参数。此处为调用eventlet.wsgi.server函数，传入sock=self._socket等参数到server函数中。其中eventlet.wsgi.server函数负责启动一个wsgi服务器程序接受客户端发来的请求，
可以参考：http://eventlet.net/doc/modules/wsgi.html?highlight=wsgi.server#eventlet.wsgi.server"""    self._server = eventlet.spawn(**wsgi_kwargs)def wait(self):    try:        """green thread阻塞等待"""        self._server.wait()    except greenlet.GreenletExit:        LOG.info(_("WSGI server has stopped."))