cinder api启动过程源码分析

1、启动cinder-api服务

当你通过cinder-api命令（如：/usr/bin/cinder-api --config-file /etc/cinder/cinder.conf）启动api服务时，执行的实际上是
cinder/cmd/api.py/main()函数， 如下：

[root@xgto02n010027244133 ~]# cat /usr/bin/cinder-api
#!/usr/bin/python2
# PBR Generated from u'console_scripts'
import sys
from cinder.cmd.api import main
if __name__ == "__main__":
    sys.exit(main())

cinder/cmd/api.py/main()函数，内容如下：

def main():

    objects.register_all() #加载辅助对象，封装与数据库相关的操作
    gmr_opts.set_defaults(CONF) #oslo_reports模块，用于生成错误报告，如内存泄漏等
    CONF(sys.argv[1:], project='cinder',
         version=version.version_string())
    config.set_middleware_defaults()
    logging.setup(CONF, "cinder")
    python_logging.captureWarnings(True)
    utils.monkey_patch() # monkey-patch，替换库比如socket、thread等，不改变import的行为，改变的是操作的指向函数

    gmr.TextGuruMeditation.setup_autorun(version, conf=CONF)
    """初始化rpc：
    设置全局Transport和Notifier,Transport是
    oslo_messaging/transport.py/Transport实例，我采用的是默认的
    rpc_backend=rabbit，所以Transport采用的driver=oslo_messaging/
    _drivers/impl_rabbit.py/RabbitDriver；Notifier是一个通知消息发
    送器，它借助Transport将通知发送发送给ceilometer
    """
    rpc.init(CONF)
	#通过服务启动器启动WSGI服务（`osapi_volume`）并等待服务启动成功
    #在初始化WSGI服务时，会设置路由映射以及加载WSGI应用程序
    #在启动WSGI服务时，会启动http监听
    launcher = service.process_launcher()
    server = service.WSGIService('osapi_volume') #创建一个名为`osapi_volume`的`WSGIService`服务对象 ，2里面详解
    launcher.launch_service(server, workers=server.workers)
    launcher.wait()

2、创建 WSGIService 服务对象

from oslo_service import wsgi
from cinder import service
cinder/service.py:class WSGIService(service.ServiceBase):
class WSGIService(service.ServiceBase):
    """Provides ability to launch API from a 'paste' configuration."""

    def __init__(self, name, loader=None):
        """Initialize, but do not start the WSGI server.
		初始化，但是并不启动wsgi server服务
        :param name: The name of the WSGI server given to the loader.
        :param loader: Loads the WSGI application using the given name.
        :returns: None

        """
        self.name = name #服务名`osapi_volume`
        self.manager = self._get_manager()  #加载名为（`osapi_volume_manager`）的管理器，返回值为None）
		#创建WSGI应用加载器，并根据配置文件(`cinder.conf`)设置应用配置路径，config_path` = `/etc/cinder/api-paste.ini‘
        self.loader = loader or wsgi.Loader(CONF) #该函数会寻找cinder.conf文件中 api_paste_config 参数对应的配置文件，并保存到变量中
        self.app = self.loader.load_app(name)  #加载WSGI应用并设置路由映射，return paste.urlmap.URLMap

		 """
		 根据配置文件(`cinder.conf`)设置监听地址及工作线程数
		 如果未指定监听ip及端口就分别设置为`0.0.0.0`及`0`
		 如果为指定工作线程数就设置为cpu个数
		 如果设置的工作线程数小于1，则抛异常
		 """
        self.host = getattr(CONF, '%s_listen' % name, "0.0.0.0")
        self.port = getattr(CONF, '%s_listen_port' % name, 0)
        self.use_ssl = getattr(CONF, '%s_use_ssl' % name, False)
        self.workers = (getattr(CONF, '%s_workers' % name, None) or
                        processutils.get_worker_count())
        if self.workers and self.workers < 1:
            worker_name = '%s_workers' % name
            msg = (_("%(worker_name)s value of %(workers)d is invalid, "
                     "must be greater than 0.") %
                   {'worker_name': worker_name,
                    'workers': self.workers})
            raise exception.InvalidInput(msg)

		"""如果CONF.profiler.enabled = True就开启性能分析
		创建一个类型为`Messaging`的通知器(`_notifier`)，将性能数据发送给
		ceilometer
		"""
        setup_profiler(name, self.host)
		##创建WSGI服务器对象
        self.server = wsgi.Server(CONF,
                                  name,
                                  self.app,
                                  host=self.host,
                                  port=self.port,
                                  use_ssl=self.use_ssl)

在cinder.conf配置文件中与cinder api服务有关的参数
# File name for the paste.deploy config for api service (string value)
api_paste_config = /etc/cinder/api-paste.ini
在初始化WSGIService服务对象过程中，主要完成了如下操作：
1)加载WSGI Application（Python Paste Deployment）
2)设置路由映射（Python Routes）
3)创建WSGI服务器对象并完成初始化

2.1 对wsgi的使用

oslo_service/wsgi.py
class Loader(object):
    """Used to load WSGI applications from paste configurations."""

    def __init__(self, conf):
        """Initialize the loader, and attempt to find the config.
        :param conf: Application config
        :returns: None
        """
        conf.register_opts(_options.wsgi_opts)
        self.config_path = None

        config_path = 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 ConfigNotFound(path=config_path)

    def load_app(self, name):
        """Return the paste URLMap wrapped WSGI application.
        :param name: Name of the application to load.
        :returns: Paste URLMap object wrapping the requested application.
        :raises: PasteAppNotFound
        """
        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:
            LOG.exception("Couldn't lookup app: %s", name)
            raise PasteAppNotFound(name=name, path=self.config_path)

配置文件api-paste.ini内容如下

[composite:osapi_volume]
use = call:cinder.api:root_app_factory
/: apiversions
/v1: openstack_volume_api_v1
/v2: openstack_volume_api_v2
/v3: openstack_volume_api_v3

[composite:openstack_volume_api_v1]
use = call:cinder.api.middleware.auth:pipeline_factory
noauth = cors http_proxy_to_wsgi request_id faultwrap sizelimit osprofiler noauth apiv1
keystone = cors http_proxy_to_wsgi request_id faultwrap sizelimit osprofiler authtoken keystonecontext apiv1
keystone_nolimit = cors http_proxy_to_wsgi request_id faultwrap sizelimit osprofiler authtoken keystonecontext apiv1

[composite:openstack_volume_api_v2]
use = call:cinder.api.middleware.auth:pipeline_factory
noauth = cors http_proxy_to_wsgi request_id faultwrap sizelimit osprofiler noauth apiv2
keystone = cors http_proxy_to_wsgi request_id faultwrap sizelimit osprofiler authtoken keystonecontext apiv2
keystone_nolimit = cors http_proxy_to_wsgi request_id faultwrap sizelimit osprofiler authtoken keystonecontext apiv2

cinder.conf文件中的api启动的配置
这三个参数控制的是api 版本的控制
# DEPRECATED: Deploy v1 of the Cinder API. (boolean value)
# This option is deprecated for remoervice_down_timeal.
# Its value may be silently ignored in the future.
#enable_v1_api = false--------不加载v1对应的app

# DEPRECATED: Deploy v2 of the Cinder API. (boolean value)
# This option is deprecated for removal.
# Its value may be silently ignored in the future.
#enable_v2_api = True------------加载v2对应的app

# Deploy v3 of the Cinder API. (boolean value)
enable_v3_api = True-------------加载v3对应的app

# The strategy to use for auth. Supports noauth or keystone. (string value)
# Allowed values: noauth, keystone
auth_strategy = keystone----------这个参数控制的api-paste.ini中选择哪一种认证方式