问题导读 1.资源的加载是如何实现的？ cinder服务启动源码分析 中，我们知道在服务类cinder.service.WSGIService的初始化过程中，有这样的源码实现： class WSGIService(object):
"""
Provides ability to launch API from a 'paste' configuration.
实现启动API的类；
"""
def __init__(self, name, loader=None):
"""
Initialize, but do not start the WSGI server.
类的初始化方法，但是不启动服务；
:param name: The name of the WSGI server given to the loader.
给定的要加载的服务的名称；
:param loader: Loads the WSGI application using the given name.
:returns: None
"""
# 给定的要加载的服务的名称；
# osapi_volume
self.name = name
# 根据给定的服务名称导入对应的管理类；
self.manager = self._get_manager()
self.loader = loader or wsgi.Loader()
self.app = self.loader.load_app(name)
# 获取主机host；
self.host = getattr(CONF, '%s_listen' % name, "0.0.0.0")
# 获取主机端口；
self.port = getattr(CONF, '%s_listen_port' % name, 0)
# Server：管理WSGI服务的类；
self.server = wsgi.Server(name,
self.app,
host=self.host,
port=self.port) 复制代码 class Loader(object):
"""
Used to load WSGI applications from paste configurations.
"""
def __init__(self, config_path=None):
"""Initialize the loader, and attempt to find the config.
:param config_path: Full or relative path to the paste config.
:returns: None
"""
# 此处指向/etc/cinder/api-paste.ini
config_path = config_path or CONF.api_paste_config
# 获取config_path的全路径；
self.config_path = utils.find_config(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: `cinder.exception.PasteAppNotFound`
加载osapi_volume程序；
"""
try:
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) 复制代码 Paste Deployment简介以及cinder-api-paste.ini的解析（1） 和Paste 中，已经进行过解析，cinder通过api-paste.ini中的配置信息来进行指定WSGI Application的实现。这里可以看到，在方法load_app中，调用了模块库deploy来实现对api-paste.ini中配置信息的解析和指定WSGI<font face="Consolas, Courier New, Courier, mono, serif" color="#000000"><span style="font-size: 12px; line-height: 18px;">def factory(cls, global_config, **local_config): </span></font>
return cls() 复制代码 class APIRouter(cinder.api.openstack.APIRouter):
"""
Routes requests on the OpenStack API to the appropriate controller
and method.
"""
ExtensionManager = extensions.ExtensionManager
def _setup_routes(self, mapper, ext_mgr):
...... 复制代码 class APIRouter(base_wsgi.Router):
def __init__(self, ext_mgr=None):
if ext_mgr is None:
if self.ExtensionManager:
ext_mgr = self.ExtensionManager() (1)
else:
raise Exception(_("Must specify an ExtensionManager class"))
mapper = ProjectMapper()
self.resources = {}
self._setup_routes(mapper, ext_mgr) (2)
self._setup_ext_routes(mapper, ext_mgr) （3）
self._setup_extensions(ext_mgr) （4）
super(APIRouter, self).__init__(mapper) （5） 复制代码 class ExtensionManager(object):
"""
Load extensions from the configured extension path.
See cinder/tests/api/extensions/foxinsocks/extension.py for an
example extension implementation.
"""
def __init__(self):
LOG.audit(_('Initializing extension manager.'))
self.extensions = {}
self._load_extensions() 复制代码 def _load_extensions(self):
"""
Load extensions specified on the command line.
"""
# extensions=['cinder.api.contrib.standard_extensions']
extensions = list(self.cls_list)
old_contrib_path = ('cinder.api.openstack.volume.contrib.'
'standard_extensions')
new_contrib_path = 'cinder.api.contrib.standard_extensions'
if old_contrib_path in extensions:
extensions = [e.replace(old_contrib_path, new_contrib_path)
for e in extensions]
for ext_factory in extensions:
try:
self.load_extension(ext_factory)
except Exception as exc:
LOG.warn(......) 复制代码 def load_extension(self, ext_factory):
"""
ext_factory=['cinder.api.contrib.standard_extensions']
"""
# ext_factory = cinder.api.contrib.standard_extensions
factory = importutils.import_class(ext_factory)
factory(self) 复制代码 def standard_extensions(ext_mgr):
extensions.load_standard_extensions(ext_mgr, LOG, __path__, __package__) 复制代码 def load_standard_extensions(ext_mgr, logger, path, package, ext_list=None):
"""
Registers all standard API extensions.
ext_mgr =
logger =
path = ['/usr/lib/python2.6/site-packages/cinder/api/contrib']
package = cinder.api.contrib
ext_list = None
"""
# our_dir = path[0] = /usr/lib/python2.6/site-packages/cinder/api/contrib
our_dir = path[0]
for dirpath, dirnames, filenames in os.walk(our_dir):
# Compute the relative package name from the dirpath
relpath = os.path.relpath(dirpath, our_dir)
if relpath == '.':
relpkg = ''
else:
relpkg = '.%s' % '.'.join(relpath.split(os.sep))
# Now, consider each file in turn, only considering .py files
for fname in filenames:
root, ext = os.path.splitext(fname)
# Skip __init__ and anything that's not .py
if ext != '.py' or root == '__init__':
continue
# Try loading it
classname = "%s%s" % (root[0].upper(), root[1:])
classpath = ("%s%s.%s.%s" % (package, relpkg, root, classname))
if ext_list is not None and classname not in ext_list:
logger.debug("Skipping extension: %s" % classpath)
continue
try:
ext_mgr.load_extension(classpath)
except Exception as exc:
logger.warn(_('Failed to load extension %(classpath)s: '
'%(exc)s'),
{'classpath': classpath, 'exc': exc})
# Now, let's consider any subdirectories we may have...
subdirs = []
for dname in dirnames:
# Skip it if it does not have __init__.py
if not os.path.exists(os.path.join(dirpath, dname, '__init__.py')):
continue
ext_name = ("%s%s.%s.extension" %
(package, relpkg, dname))
try:
ext = importutils.import_class(ext_name)
except ImportError:
# extension() doesn't exist on it, so we'll explore
# the directory for ourselves
subdirs.append(dname)
else:
try:
ext(ext_mgr)
except Exception as exc:
logger.warn(_('Failed to load extension %(ext_name)s: %(exc)s), {'ext_name': ext_name, 'exc': exc})
# Update the list of directories we'll explore...
dirnames[:] = subdirs 复制代码 def load_extension(self, ext_factory):
"""
Execute an extension factory.
"""
LOG.debug(_("Loading extension %s"), ext_factory)
# Load the factory
factory = importutils.import_class(ext_factory)
# Call it
LOG.debug(_("Calling extension factory %s"), ext_factory)
factory(self) 复制代码 class Backups(extensions.ExtensionDescriptor):
"""Backups support."""
name = 'Backups'
alias = 'backups'
namespace = 'http://docs.openstack.org/volume/ext/backups/api/v1'
updated = '2012-12-12T00:00:00+00:00'
def get_resources(self):
resources = []
res = extensions.ResourceExtension(
Backups.alias,
BackupsController(),
collection_actions={'detail': 'GET'},
member_actions={'restore': 'POST'})
resources.append(res)
return resources 复制代码 class ExtensionDescriptor(object):
"""
Base class that defines the contract for extensions.
Note that you don't have to derive from this class to have a valid
extension; it is purely a convenience.
API扩展描述的基类；
"""
name = None
alias = None
namespace = None
updated = None
def __init__(self, ext_mgr):
"""
Register extension with the extension manager.
"""
ext_mgr.register(self) 复制代码 def register(self, ext):
# Do nothing if the extension doesn't check out
if not self._check_extension(ext):
return
alias = ext.alias
LOG.audit(_('Loaded extension: %s'), alias)
if alias in self.extensions:
raise exception.Error("Found duplicate extension: %s" % alias)
self.extensions[alias] = ext 复制代码 相关文章 OpenStack Cinder服务启动过程中的资源加载和扩展源码解析之二 http://www.aboutyun.com/thread-10223-1-1.html OpenStack Cinder服务启动过程中的资源加载和扩展源码解析之三 http://www.aboutyun.com/thread-10224-1-1.html http://blog.csdn.net/gaoxingnengjisuan/article/details/21722111 
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