asyncio "任务已被破坏，但它正在等待处理！"在 pysnmp 示例程序中

Posted 2023-03-14

【中文标题】asyncio "任务已被破坏，但它正在等待处理！"在 pysnmp 示例程序中

【英文标题】：asyncio "Task was destroyed but it is pending!" in pysnmp sample program

【发布时间】：2017-01-08 23:57:25

【问题描述】：

我正在测试 pysnmp asyncio 模块，一开始使用的是随文档一起提供的sample program。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，但找不到我的（没有经验的）眼睛有什么问题。我在 Debian 8.5 上使用 Python 3.4.2 和随附的 asyncio 以及 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>

 

非常感谢任何帮助解决这个问题！

谢谢。

【问题讨论】：

这看起来像 pysnmp 中与关闭时定期定时器功能取消有关的错误。这是有关此事的更多信息docs.python.org/3/library/…。在 github 上打开问题或发送 PR 可能是一种方法。 ;)

谢谢！让我打开一个问题。

【参考方案1】：

pysnmp 中有一个内部计时器函数，用于处理缓存、重试等。使用异步传输，该计时器由 asyncio Future 驱动。您观察到的消息警告您，在主循环关闭之前，Future 对象仍处于挂起状态。

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 [hackerish] 方法是将以下 sn-p 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。