Openstack Periodic Task
Openstack Periodic Task
周期性任务在各个模块的manager.py（computer，scheduler，cell，network）中添加。
添加方法：在模块manager类实现中添加方法，并用装饰器periodic_task.periodic_task装饰。
实现机制
以ComputerManager类为例。
模块mananger类添加方法
在资源上报方法为例，装饰器指定该方法为周期性任务，并通过spacing参数指定任务执行间隔，不指定spacing参数则默认为60.0s。
nova.computer.manager.ComputerManager
@periodic_task.periodic_task(spacing=CONF.update_resources_interval)
def update_available_resource
…periodic_task装饰器
periodic_task装饰器指明方法是周期性任务，并给周期性方法增加一些属性，包括周期型任务名称，任务执行间隔等。
oslo_service.periodic_task.periodic_task
def periodic_task(*args, **kwargs):
...Manager类继承关系
nova.computer.manager.ComputerManager
nova.manager.Manager
nova.manager.PeriodicTask
oslo_service.periodic_task.PeriodicTask
PeriodicTask类对象通过元类PeriodicTasksMeta创建。
@six.add_metaclass(_PeriodicTasksMeta)
class PeriodicTasks(object):
...PeriodicTasksMeta元类
PeriodicTasksMeta元类收集模块manager类中定义的周期性任务，并保存在_periodic_tasks列表中。
oslo_service.PeriodicTasksMeta
DEFAULT_INTERVAL = 60.0
class _PeriodicTasksMeta(type):
def _add_periodic_task(cls, task):
"""Add a periodic task to the list of periodic tasks.
The task should already be decorated by @periodic_task.
:return: whether task was actually enabled
"""
name = task._periodic_name
…
if task._periodic_spacing == 0:
task._periodic_spacing = DEFAULT_INTERVAL
cls._periodic_tasks.append((name, task))
cls._periodic_spacing[name] = task._periodic_spacing
return True
def init(cls, names, bases, dict_):
"""Metaclass that allows us to collect decorated periodic tasks."""
…
for value in cls.dict.values():
if getattr(value, '_periodic_task', False):
cls._add_periodic_task(value)
触发执行周期性任务
Computer进程启动时调用service的start方法，start方法中创建定时器，定时执行periodic_tasks方法。
1、nova.service.Service.
class Service(service.Service):
"""Service object for binaries running on hosts.
def start(self):
…
if self.periodic_enable:
if self.periodic_fuzzy_delay:
initial_delay = random.randint(0, self.periodic_fuzzy_delay)
else:
initial_delay = None
self.tg.add_dynamic_timer(self.periodic_tasks,
initial_delay=initial_delay,
periodic_interval_max=
self.periodic_interval_max)
def periodic_tasks(self, raise_on_error=False):
"""Tasks to be run at a periodic interval."""
ctxt = context.get_admin_context()
return self.manager.periodic_tasks(ctxt, raise_on_error=raise_on_error)2、nova.manager.Manger
class Manager(base.Base, PeriodicTasks):
def periodic_tasks(self, context, raise_on_error=False):
"""Tasks to be run at a periodic interval."""
return self.run_periodic_tasks(context, raise_on_error=raise_on_error)3、oslo_service.periodic_task.PeriodicTask
run_periodic_tasks方法遍历执行_periodic_tasks中收集的周期性任务。
class PeriodicTasks(object):
def run_periodic_tasks(self, context, raise_on_error=False):
"""Tasks to be run at a periodic interval."""
idle_for = DEFAULT_INTERVAL
for task_name, task in self._periodic_tasks:
if (task._periodic_external_ok and not
self.conf.run_external_periodic_tasks):
continue
cls_name = reflection.get_class_name(self, fully_qualified=False)
full_task_name = '.'.join([cls_name, task_name])
spacing = self._periodic_spacing[task_name]
last_run = self._periodic_last_run[task_name]
# Check if due, if not skip
idle_for = min(idle_for, spacing)
if last_run is not None:
delta = last_run + spacing - now()
if delta > 0:
idle_for = min(idle_for, delta)
continue
LOG.debug("Running periodic task %(full_task_name)s",
{"full_task_name": full_task_name})
self._periodic_last_run[task_name] = _nearest_boundary(
last_run, spacing)
try:
task(self, context)
except Exception:
if raise_on_error:
raise
LOG.exception(_LE("Error during %(full_task_name)s"),
{"full_task_name": full_task_name})
time.sleep(0)
return idle_for