asyncio“任务已被销毁，但正在等待处理！”在 pysnmp 示例程序中

Question

我正在测试 pysnmp asyncio 模块，并开始使用随文档一起提供的 示例程序。当我运行示例程序时，它给出了

Task was destroyed but it is pending!

错误。我检查了类似的问题，但找不到我（缺乏经验的）眼睛的问题。我正在使用 Python 3.4.2 和它附带的 asyncio 以及 Debian 8.5 上的 pysnmp (4.3.2)

我使用的程序（与pysnmp文档中的示例程序相同）

 
    import asyncio
    from pysnmp.hlapi.asyncio import *


    @asyncio.coroutine
    def getone(snmpEngine, hostname):
        errorIndication, errorStatus, errorIndex, varBinds = yield from getCmd(
            snmpEngine,
            CommunityData('public'),
            UdpTransportTarget(hostname),
            ContextData(),
            ObjectType(ObjectIdentity('SNMPv2-MIB', 'sysDescr', 0))
        )

        if errorIndication:
            print(errorIndication)
        elif errorStatus:
            print('%s at %s' % (
                errorStatus.prettyPrint(),
                errorIndex and varBinds[int(errorIndex) - 1][0] or '?'
            )
                  )
        else:
            for varBind in varBinds:
                print(' = '.join([x.prettyPrint() for x in varBind]))


    @asyncio.coroutine
    def getall(snmpEngine, hostnames):
        for hostname in hostnames:
            yield from getone(snmpEngine, hostname)


    snmpEngine = SnmpEngine()

    loop = asyncio.get_event_loop()
    loop.run_until_complete(getall(snmpEngine, [('demo.snmplabs.com', 1161),
                                                ('demo.snmplabs.com', 2161),
                                                ('demo.snmplabs.com', 3161)]))
  

错误是：

 

     Executing  wait_for= cb=[_raise_stop_error() at /usr/lib/python3.4/asyncio/base_event
    s.py:101] created at /usr/lib/python3.4/asyncio/base_events.py:264> took 0.460 seconds
    SNMPv2-MIB::sysDescr.0 = SunOS zeus.snmplabs.com 4.1.3_U1 1 sun4m
    SNMPv2-MIB::sysDescr.0 = SunOS zeus.snmplabs.com 4.1.3_U1 1 sun4m
    SNMPv2-MIB::sysDescr.0 = SunOS zeus.snmplabs.com 4.1.3_U1 1 sun4m
    Task was destroyed but it is pending!
    source_traceback: Object created at (most recent call last):
      File "multiple-sequential-queries.py", line 58, in 
        ('demo.snmplabs.com', 3161)]))   
      File "/usr/lib/python3.4/asyncio/base_events.py", line 271, in run_until_complete
        self.run_forever()
      File "/usr/lib/python3.4/asyncio/base_events.py", line 244, in run_forever
        self._run_once()
      File "/usr/lib/python3.4/asyncio/base_events.py", line 1075, in _run_once
        handle._run()
      File "/usr/lib/python3.4/asyncio/events.py", line 120, in _run
        self._callback(*self._args)
      File "/usr/lib/python3.4/asyncio/tasks.py", line 237, in _step
        result = next(coro)
      File "/usr/lib/python3.4/asyncio/coroutines.py", line 79, in __next__
        return next(self.gen)
      File "multiple-sequential-queries.py", line 50, in getall
        yield from getone(snmpEngine, hostname)
      File "/usr/lib/python3.4/asyncio/coroutines.py", line 79, in __next__
        return next(self.gen)
      File "multiple-sequential-queries.py", line 31, in getone
        ObjectType(ObjectIdentity('SNMPv2-MIB', 'sysDescr', 0))
      File "/usr/lib/python3.4/asyncio/coroutines.py", line 79, in __next__
        return next(self.gen)
      File "/usr/lib/python3.4/asyncio/coroutines.py", line 141, in coro
        res = func(*args, **kw)
      File "/usr/local/lib/python3.4/dist-packages/pysnmp/hlapi/asyncio/cmdgen.py", line 138, in getCmd
        addrName, paramsName = lcd.configure(snmpEngine, authData, transportTarget)
      File "/usr/local/lib/python3.4/dist-packages/pysnmp/hlapi/lcd.py", line 87, in configure
        transport
      File "/usr/local/lib/python3.4/dist-packages/pysnmp/entity/config.py", line 308, in addTransport
        transport)
      File "/usr/local/lib/python3.4/dist-packages/pysnmp/carrier/asyncio/dispatch.py", line 70, in registerTransport
        self.loopingcall = asyncio.async(self.handle_timeout())
    task: :4> wait_for= created at /usr/local/lib/python3.4/dist-packages/pysnmp/carrier/asyncio/dispatch.py:70>

 

非常感谢任何解决此问题的帮助！

谢谢。

Answer 1

pysnmp 中有一个内部计时器函数，用于处理缓存、重试等。使用 asyncio 传输时，计时器由 asyncio 驱动

Future

。您观察到的消息警告您，在主循环关闭之前，Future 对象仍处于待处理状态。

要解决此问题，您需要在完成所有 SNMP I/O 后取消挂起的计时器任务。一种[黑客]方法是将以下代码片段附加到您提到的示例脚本中：

...

snmpEngine = SnmpEngine()

loop = asyncio.get_event_loop()

loop.run_until_complete(getall(snmpEngine, [('demo.snmplabs.com', 1161),
                                            ('demo.snmplabs.com', 2161),
                                            ('demo.snmplabs.com', 3161)]))

# run a coroutine to cancel pending timer task

from pysnmp.hlapi.asyncore.cmdgen import lcd

@asyncio.coroutine
def unconfigure(snmpEngine, authData=None):
    lcd.unconfigure(snmpEngine, authData)

loop.run_until_complete(unconfigure(snmpEngine))

我正在努力将类似的协程添加到 pysnmp 中，以便您可以开箱即用地运行它。

Answer 2

作为这个库的新维护者，我们团队与 Ilya 持有不同的意见。

就像我们在这个 GitHub 问题中解释的那样，

SnmpEngine

类型的用户应该通过调用

SnmpEngine.transportDispatcher.closeDispatcher()

来显式释放资源（包括任务）。