我们通过 rest api 可以访问、删除、创造 neutron 的资源，那么当我们通过 rest api 发起一个请求时，后台是如何处理这个请求的？本文就来探讨这个问题。
curl -s -X GET http://172.16.100.106:9696/v2.0/networks \
-H "Content-Type: application/json" \
-H "X-Auth-Token: 7eb90d76addc4a5bafeb380bf47f37fd"
RESOURCES = {'network': 'networks',
'subnet': 'subnets',
'subnetpool': 'subnetpools',
'port': 'ports'}
SUB_RESOURCES = {}
COLLECTION_ACTIONS = ['index', 'create']
MEMBER_ACTIONS = ['show', 'update', 'delete']
REQUIREMENTS = {'id': constants.UUID_PATTERN, 'format': 'json'}
col_kwargs = dict(collection_actions=COLLECTION_ACTIONS,
member_actions=MEMBER_ACTIONS)
def _map_resource(collection, resource, params, parent=None):
allow_bulk = cfg.CONF.allow_bulk
allow_pagination = cfg.CONF.allow_pagination
allow_sorting = cfg.CONF.allow_sorting
controller = base.create_resource(
collection, resource, plugin, params, allow_bulk=allow_bulk,
parent=parent, allow_pagination=allow_pagination,
allow_sorting=allow_sorting)
path_prefix = None
if parent:
path_prefix = "/%s/{%s_id}/%s" % (parent['collection_name'],
parent['member_name'],
collection)
mapper_kwargs = dict(controller=controller,
requirements=REQUIREMENTS,
path_prefix=path_prefix,
**col_kwargs)
return mapper.collection(collection, resource,
**mapper_kwargs)
for resource in RESOURCES:
_map_resource(RESOURCES[resource], resource,
attributes.RESOURCE_ATTRIBUTE_MAP.get(
RESOURCES[resource], dict()))
resource_registry.register_resource_by_name(resource)
for resource in SUB_RESOURCES:
_map_resource(SUB_RESOURCES[resource]['collection_name'], resource,
attributes.RESOURCE_ATTRIBUTE_MAP.get(
SUB_RESOURCES[resource]['collection_name'],
dict()),
SUB_RESOURCES[resource]['parent'])
**作用：**对 routes.Mapper().collection 方法的封装，建立映射关系。
allow_bulk允许使用批量API（比如说我们可通过 reset api 批量创建网络）；allow_paginaion允许使用分页（已被丢弃的选项，恒为 True）;allow_sorting允许使用排序（已被丢弃的选项，恒为 True）;
# Allow the usage of the bulk API (boolean value)
#allow_bulk = true
# DEPRECATED: Allow the usage of the pagination. This option has been
# deprecated and will now be enabled unconditionally. (boolean value)
# This option is deprecated for removal.
# Its value may be silently ignored in the future.
#allow_pagination = true
# DEPRECATED: Allow the usage of the sorting. This option has been deprecated
# and will now be enabled unconditionally. (boolean value)
# This option is deprecated for removal.
# Its value may be silently ignored in the future.
#allow_sorting = true
import routes
map = routes.Mapper()
collection = 'entries'
resource = 'entry'
controller = dict()
path_prefix = None
requirements = {'id': 'id', 'format': 'json'}
collection_actions = ['index', 'create']
member_actions = ['show', 'update', 'delete']
mapper_kwargs = dict(controller = controller,
requirements = requirements,
path_prefix = path_prefix,
collection_actions = collection_actions,
member_actions = member_actions)
map.collection(collection, resource, **mapper_kwargs)
那么我们构造的映射关系如下：
>>> print map
Route name Methods Path Controller action
entries GET /entries{.format} {} index
create_entry POST /entries{.format} {} create
entry GET /entries/{id}{.format} {} show
update_entry PUT /entries/{id}{.format} {} update
delete_entry DELETE /entries/{id}{.format} {} delete
create_resource很简单，就是实现了一个 Controller 实例，并返回了一个 把 Controller 实例进行包装的 Resource实例。
def create_resource(collection, resource, plugin, params, allow_bulk=False,
member_actions=None, parent=None, allow_pagination=False,
allow_sorting=False):
controller = Controller(plugin, collection, resource, params, allow_bulk,
member_actions=member_actions, parent=parent,
allow_pagination=allow_pagination,
allow_sorting=allow_sorting)
return wsgi_resource.Resource(controller, FAULT_MAP)
neutron.api.v2.base.py 就是实现了 Contrller 类和 create_resource 方法。
Controller** 是 neutron 中 wsgi 实现的关键类，我们一点点分析。**
我们不是 neutron 架构的设计者，单看这个类的实现是很难理解其用处的，我么就结合其使用来看（见上面）。
class Controller(object):
LIST = 'list'
SHOW = 'show'
CREATE = 'create'
UPDATE = 'update'
DELETE = 'delete'
@property
def plugin(self):
return self._plugin
@property
def resource(self):
return self._resource
@property
def attr_info(self):
return self._attr_info
@property
def member_actions(self):
return self._member_actions
def _init_policy_attrs(self):
"""Create the list of attributes required by policy.
If the attribute map contains a tenant_id policy, then include
project_id to bring the resource into the brave new world.
:return: sorted list of attributes required by policy
"""
policy_attrs = {name for (name, info) in self._attr_info.items()
if info.get('required_by_policy')}
if 'tenant_id' in policy_attrs:
policy_attrs.add('project_id')
# Could use list(), but sorted() makes testing easier.
return sorted(policy_attrs)
def __init__(self, plugin, collection, resource, attr_info,
allow_bulk=False, member_actions=None, parent=None,
allow_pagination=False, allow_sorting=False):
if member_actions is None:
member_actions = []
self._plugin = plugin
self._collection = collection.replace('-', '_')
self._resource = resource.replace('-', '_')
self._attr_info = attr_info
self._allow_bulk = allow_bulk
self._allow_pagination = allow_pagination
self._allow_sorting = allow_sorting
self._native_bulk = self._is_native_bulk_supported()
self._native_pagination = self._is_native_pagination_supported()
self._native_sorting = self._is_native_sorting_supported()
self._policy_attrs = self._init_policy_attrs()
self._notifier = n_rpc.get_notifier('network')
self._member_actions = member_actions
self._primary_key = self._get_primary_key()
if self._allow_pagination and self._native_pagination:
# Native pagination need native sorting support
if not self._native_sorting:
raise exceptions.Invalid(
_("Native pagination depend on native sorting")
)
if not self._allow_sorting:
LOG.info(_LI("Allow sorting is enabled because native "
"pagination requires native sorting"))
self._allow_sorting = True
self.parent = parent
if parent:
self._parent_id_name = '%s_id' % parent['member_name']
parent_part = '_%s' % parent['member_name']
else:
self._parent_id_name = None
parent_part = ''
self._plugin_handlers = {
self.LIST: 'get%s_%s' % (parent_part, self._collection),
self.SHOW: 'get%s_%s' % (parent_part, self._resource)
}
for action in [self.CREATE, self.UPDATE, self.DELETE]:
self._plugin_handlers[action] = '%s%s_%s' % (action, parent_part,
self._resource)
-
_init_policy_attrs创建一个 policy 所需要的属性列表。 -
__init__方法主要是做了一些属性初始化的工作，一个主要的工作就是构造self._plugin_handlers。- 如果我们的
self._collection为ports，self._resource为port，self.parent为None，那么我们得到的self._plugin_handlers将会是：
- 如果我们的
self._plugin_handlers = {
self.list : get_ports,
self.show : get_port,
self.create : create_port,
self.update : update_port,
self.delete : delete_port}
def _get_primary_key(self, default_primary_key='id'):
for key, value in six.iteritems(self._attr_info):
if value.get('primary_key', False):
return key
return default_primary_key
def _is_native_bulk_supported(self):
native_bulk_attr_name = ("_%s__native_bulk_support"
% self._plugin.__class__.__name__)
return getattr(self._plugin, native_bulk_attr_name, False)
def _is_native_pagination_supported(self):
return api_common.is_native_pagination_supported(self._plugin)
def _is_native_sorting_supported(self):
return api_common.is_native_sorting_supported(self._plugin)
def __getattr__(self, name):
if name in self._member_actions:
@db_api.retry_db_errors
def _handle_action(request, id, **kwargs):
arg_list = [request.context, id]
# Ensure policy engine is initialized
policy.init()
# Fetch the resource and verify if the user can access it
try:
parent_id = kwargs.get(self._parent_id_name)
resource = self._item(request,
id,
do_authz=True,
field_list=None,
parent_id=parent_id)
except oslo_policy.PolicyNotAuthorized:
msg = _('The resource could not be found.')
raise webob.exc.HTTPNotFound(msg)
body = kwargs.pop('body', None)
# Explicit comparison with None to distinguish from {}
if body is not None:
arg_list.append(body)
# It is ok to raise a 403 because accessibility to the
# object was checked earlier in this method
policy.enforce(request.context,
name,
resource,
pluralized=self._collection)
ret_value = getattr(self._plugin, name)(*arg_list, **kwargs)
# It is simply impossible to predict whether one of this
# actions alters resource usage. For instance a tenant port
# is created when a router interface is added. Therefore it is
# important to mark as dirty resources whose counters have
# been altered by this operation
resource_registry.set_resources_dirty(request.context)
return ret_value
return _handle_action
else:
raise AttributeError()