python twisted deferredlist ErrorBack（Deferred中未处理的错误）

Question

在我下面的代码中，我通过了主机：端口组合并尝试使用twisted Defered从服务器获取一些信息。我已经展示了我要做的事情的一个非常基本的代码。通过httplib连接到主机端口。如果主机启动，它将正常工作。调用正确的回调方法。但是当它失败时（当检索url失败时），它不会进入printError函数。我得到'Unhandled error in Deferred'错误，循环停止。请告诉我怎样才能摆脱这个错误。请提供解决方案。在

import httplib, time, sys

from twisted.internet import reactor, defer, task

from twisted.python import log

class Getter:

    def gotResults(self, x):

        ( host, port ) = x.split(":")
        conn = httplib.HTTPConnection( host, port )

        try :
            conn.request ( 'GET', '/get/data/' )
            response = conn.getresponse()
            self.d.callback ( response )
        except ( httplib.HTTPException ) :
            self.d.errback(ValueError("Error Connecting"))



    def getDummyData(self, x):
        currTime = time.strftime( "%H:%M:%S" )
        print currTime
        self.d = defer.Deferred()
        self.gotResults(x)
        return self.d



def printData(data):

    for d in data:
        print "Results %s %s" % ( str(d[1].status), str(d[1].reason)  )

def printError(data):

    print data



def testmessage():
# this series of callbacks and errbacks will print an error message
    g = Getter()
    deferred1 = g.getDummyData( 'valid_hostname1:port1' )
    # this should go to printData

    g = Getter()
    deferred2 = g.getDummyData('invalid_hostname2:port2')
    # this should go to printError

    d1 = defer.DeferredList ( [ deferred1, deferred2 ] )
    d1.addCallback ( printData )
    d1.addErrback  ( printError )



x = task.LoopingCall ( testmessage )
x.start ( 1 )
reactor.callLater(300, reactor.stop);
reactor.run()

Answer 1

问题是您假设conn.request（在第17行）将引发一个httplib.HTTPException，但这不是它引发的异常类型。由于您不太确定它将引发什么异常，所以我建议您使用一个覆盖的except...语句，并从sys.exc_info()获取异常数据。在

按照以下路线固定：

import httplib, time, sys

from twisted.internet import reactor, defer, task

from twisted.python import log

class Getter:

    def gotResults(self, x):

        ( host, port ) = x.split(":")
        conn = httplib.HTTPConnection( host, port )

        try :
            conn.request ( 'GET', '/get/data/' )
            response = conn.getresponse()
            self.d.callback ( response )
        except:
            self.d.errback(sys.exc_info())


    def getDummyData(self, x):
        currTime = time.strftime( "%H:%M:%S" )
        print currTime
        self.d = defer.Deferred()
        self.gotResults(x)
        return self.d



def printData(data):

    for d in data:
        print "Results %s %s" % ( str(d[1].status), str(d[1].reason)  )

def printError(data):

    print data



def testmessage():
# this series of callbacks and errbacks will print an error message
    g = Getter()
    deferred1 = g.getDummyData( 'valid_hostname1:port1' )
    # this should go to printData

    g = Getter()
    deferred2 = g.getDummyData('invalid_hostname2:port2')
    # this should go to printError

    d1 = defer.DeferredList ( [ deferred1, deferred2 ] )
    d1.addCallback ( printData )
    d1.addErrback  ( printError )



x = task.LoopingCall ( testmessage )
x.start ( 1 )
reactor.callLater(300, reactor.stop);
reactor.run()