qos.py
QosAgentDriver类
主要定义了QoS agent driver的抽象接口，并定义了create、update、delete方法，这个方法需要一定的参数，包括具体的action、port和qos_policy。对于QosAgent来说
主要通过实现QoS agent driver的抽象接口来调用QoS agent driver实现相应的QOS policy。
# 定义抽象的接口
@abc.abstractmethod
def initialize(self):
"""Perform QoS agent driver initialization.
"""
def create(self, port, qos_policy):
"""Apply QoS rules on port for the first time.
:param port: port object.
:param qos_policy: the QoS policy to be applied on port.
"""
self._handle_update_create_rules('create', port, qos_policy)
def update(self, port, qos_policy):
"""Apply QoS rules on port.
:param port: port object.
:param qos_policy: the QoS policy to be applied on port.
"""
self._handle_update_create_rules('update', port, qos_policy)
def delete(self, port, qos_policy=None):
"""Remove QoS rules from port.
:param port: port object.
:param qos_policy: the QoS policy to be removed from port.
"""
if qos_policy is None:
rule_types = self.SUPPORTED_RULES
else:
rule_types = set(
[rule.rule_type
for rule in self._iterate_rules(qos_policy.rules)])
for rule_type in rule_types:
self._handle_rule_delete(port, rule_type)
下面具体来看_handle_update_create_rules()方法，这是一个内部类的方法，主要就是更新一下创建的policy规则。
def _handle_update_create_rules(self, action, port, qos_policy):
for rule in self._iterate_rules(qos_policy.rules):
if rule.should_apply_to_port(port):
# handler的rule类型和qos driver定义保持一致，包括create_、update_、delete_
handler_name = "".join((action, "_", rule.rule_type))
# Get a named attribute from an object; getattr(x, 'y') is equivalent to x.y.
handler = getattr(self, handler_name)
handler(port, rule)
else:
LOG.debug("Port %(port)s excluded from QoS rule %(rule)s",
{'port': port, 'rule': rule.id})
_iterate_rules()是一个有关rule的generator
def _iterate_rules(self, rules):
for rule in rules:
rule_type = rule.rule_type
# qos driver应该定义好可以支持的rules类型，包括create_、update_、delete_等，并与handler保持一致，这里使用yield来定义有关rule的generator。
if rule_type in self.SUPPORTED_RULES:
yield rule
else:
LOG.warning(_LW('Unsupported QoS rule type for %(rule_id)s: '
'%(rule_type)s; skipping'),
{'rule_id': rule.id, 'rule_type': rule_type})
PortPolicyMap类
主要实现port和policy之间的映射，比如将port绑定到新的policy，并返回该port的所有policy，或者将port和之前的policy分离，并删除有关该policy的所有数据。
def set_port_policy(self, port, policy):
# 将port和policy进行绑定
"""Attach a port to policy and return any previous policy on port."""
port_id = port['port_id']
old_policy = self.get_port_policy(port)
self.known_policies[policy.id] = policy
self.port_policies[port_id] = policy.id
# port和policy进行绑定
self.qos_policy_ports[policy.id][port_id] = port
if old_policy and old_policy.id != policy.id:
del self.qos_policy_ports[old_policy.id][port_id]
return old_policy
QosAgentExtension类
继承父类agent_extension.AgentCoreResourceExtension，并覆盖了原有的一些方法。
SUPPORTED_RESOURCES = [resources.QOS_POLICY]
def initialize(self, connection, driver_type):
"""Perform Agent Extension initialization.
"""
# 初始化qos_driver的RPC消息通信，实现了server端的CallBack
self.resource_rpc = resources_rpc.ResourcesPullRpcApi()
# 调用NeutronManager的load_class_for_provider方法
# namespace是'neutron.qos.agent_drivers'，plugin_provider就是driver_type
self.qos_driver = manager.NeutronManager.load_class_for_provider(
'neutron.qos.agent_drivers', driver_type)()
self.qos_driver.initialize()
# 映射port和policy之间的关系
self.policy_map = PortPolicyMap()
# 定义resources.QOS_POLICY的callback，即_handle_notification
registry.subscribe(self._handle_notification, resources.QOS_POLICY)
# 定义consumer的RPC通信连接，这里应该就是server端
self._register_rpc_consumers(connection)
这里其实还存在一个问题，就是如何根据resource_type生成具体的callback方法，上面的resource_type对应的就是resources.QOS_POLICY，而neutron.api.rpc.callbacks.consumer中的subscribe()方法如下所示：
def _get_manager():
return resource_manager.ConsumerResourceCallbacksManager()
def subscribe(callback, resource_type):
_get_manager().register(callback, resource_type)
neutron.api.rpc.callbacks.comsumer是继承了父类neutron.api.rpc.callbacks，而subscribe()也是调用了ConsumerResourceCallbacksManager()的类方法，ConsumerResourceCallbacksManager类继承了父类ResourceCallbacksManager，父类的register方法如下：
def register(self, callback, resource_type):
"""Register a callback for a resource type.
:param callback: the callback. It must raise or return NeutronObject.
:param resource_type: must be a valid resource type.
"""
LOG.debug("Registering callback for %s", resource_type)
_validate_resource_type(resource_type)
self._add_callback(callback, resource_type)
但是_add_callback()是一个抽象接口，具体实现是在ConsumerResourceCallbacksManager类中，
def _add_callback(self, callback, resource_type):
self._callbacks[resource_type].add(callback)
即生成一个带有resource_type和callback的set集合，到此就已经注册好了一个指定resource_type类型的callback方法。
handle_port()方法的具体实现
@lockutils.synchronized('qos-port')
def handle_port(self, context, port):
"""Handle agent QoS extension for port.
This method applies a new policy to a port using the QoS driver.
Update events are handled in _handle_notification.
"""
port_id = port['port_id']
port_qos_policy_id = port.get('qos_policy_id')
network_qos_policy_id = port.get('network_qos_policy_id')
qos_policy_id = port_qos_policy_id or network_qos_policy_id
if qos_policy_id is None:
self._process_reset_port(port)
return
if not self.policy_map.has_policy_changed(port, qos_policy_id):
return
qos_policy = self.resource_rpc.pull(
context, resources.QOS_POLICY, qos_policy_id)
if qos_policy is None:
LOG.info(_LI("QoS policy %(qos_policy_id)s applied to port "
"%(port_id)s is not available on server, "
"it has been deleted. Skipping."),
{'qos_policy_id': qos_policy_id, 'port_id': port_id})
self._process_reset_port(port)
else:
old_qos_policy = self.policy_map.set_port_policy(port, qos_policy)
if old_qos_policy:
self.qos_driver.delete(port, old_qos_policy)
self.qos_driver.update(port, qos_policy)
else:
self.qos_driver.create(port, qos_policy)
python学习小结：有关yield的用法。当一个函数包含了yield，那么表示该函数已经是一个generator。在Python中，这种一边循环一边计算的机制，称为生成器（Generator），generator和函数的执行流程不一样。函数是顺序执行，遇到return语句或者最后一行函数语句就返回。而变成generator的函数，在每次调用next()的时候执行，遇到yield语句返回，再次执行时从上次返回的yield语句处继续执行。