python - 扭曲的延迟以不期望的方式触发

Question

我有以下代码

# logging
from twisted.python import log

import sys

# MIME Multipart handling
import email
import email.mime.application
import uuid

# IMAP Connection
from twisted.mail import imap4
from twisted.internet import protocol


#SMTP Sending
import os.path
from OpenSSL.SSL import SSLv3_METHOD
from twisted.internet import ssl
from twisted.mail.smtp import ESMTPSenderFactory
from twisted.internet.ssl import ClientContextFactory
from twisted.internet.defer import Deferred
from twisted.internet import reactor

#class AccountsManager(object):


def connectToIMAPServer(imap_server, username, password):
    factory = IMAP4ClientFactory(username, password, login_insecure = True)

    host, port = imap_server.split(":")

    # connect to reactor
    if port == '993':
        reactor.connectSSL(host, int(port), factory, ssl.ClientContextFactory())
    else:
        if not port:
            port = 143
        reactor.connectTCP(host, int(port), factory)

    d = factory.deferred
    d.addCallback(lambda r: factory.proto)

    return d

class IMAP4Client(imap4.IMAP4Client):
    """
        A client with callbacks for greeting messages from an IMAP server.
        """
    greetDeferred = None

    def serverGreeting(self, caps):
        self.serverCapabilities = caps
        if self.greetDeferred is not None:
            d, self.greetDeferred = self.greetDeferred, None
            d.callback(self)

class IMAP4ClientFactory(protocol.ClientFactory):
    usedUp = False

    protocol = IMAP4Client


    def __init__(self, username, password, mailbox = "INBOX", login_insecure = False):
        self.ctx = ssl.ClientContextFactory()

        self.username = username
        self.password = password
        self.mailbox  = mailbox
        self.login_insecure = login_insecure

        self.deferred = Deferred()

    def buildProtocol(self, addr):
        """
            Initiate the protocol instance. Since we are building a simple IMAP
            client, we don't bother checking what capabilities the server has. We
            just add all the authenticators twisted.mail has.  Note: Gmail no
            longer uses any of the methods below, it's been using XOAUTH since
            2010.
            """
        assert not self.usedUp
        self.usedUp = True

        p = self.protocol(self.ctx)
        p.factory = self

        p.greetDeferred = self.deferred

        p.registerAuthenticator(imap4.PLAINAuthenticator(self.username))
        p.registerAuthenticator(imap4.LOGINAuthenticator(self.username))
        p.registerAuthenticator(imap4.CramMD5ClientAuthenticator(self.username))

        self.deferred.addCallback(self.GreetingCallback)
        self.deferred.addErrback(self.GreetingErrback)

        self.proto = p

        return p

    def GreetingCallback(self, result):
        print "Secure Login"
        auth_d = self.proto.authenticate(self.password)
        auth_d.addCallback(self.AuthenticationCallback)
        auth_d.addErrback(self.AuthenticationErrback)

        return auth_d # attach it to the main deferred

    def GreetingErrback(self, error):
        log.err(error)
        self.CloseConnection()
        return error

    def AuthenticationCallback(self, result):
        print "Selecting Mailbox"
        d = self.proto.examine(self.mailbox)
        return d

    def AuthenticationErrback(self, failure):
        if self.login_insecure:
            failure.trap(imap4.NoSupportedAuthentication)
            return self.InsecureLogin()
        else:
            return error

    def InsecureLogin(self):
        print "Insecure Login"
        d = self.proto.login(self.username, self.password)
        d.addCallback(self.AuthenticationCallback)
        return d

    def CloseConnection(self):
        self.proto.transport.loseConnection()

    def clientConnectionFailed(self, connector, reason):
        d, self.deferred = self.deferred, None
        d.errback(reason)


class MailServer(object):
    "Manages a server"

    size = 0
    used_space = 0


    def __init__(self, smtp_server, imap_server, username, password):
        self.smtp_server, self.smtp_port = smtp_server.split(":")
        self.imap_server, self.imap_port = imap_server.split(":")
        self.username = username
        self.password = password

        self.imap_connection = IMAP4ClientFactory(username, password)


    def upload_data(self, data):
        """
        Uploads data to email server returns deferred that will return with the imap uid
        """

        # Create a text/plain message
        id = str(uuid.uuid4()).upper()

        msg = email.mime.Multipart.MIMEMultipart()
        msg['Subject'] = 'GMA ID: %s' % id
        msg['From'] = self.email_address
        msg['To'] = self.email_address

        # The main body is just another attachment
        body = email.mime.Text.MIMEText("GMA ID: %s" % (self.uuid_id))
        msg.attach(body)
        att = email.mime.application.MIMEApplication(data,_subtype="raw")
        att.add_header('Content-Disposition','attachment',filename = os.path.basename(self.filename))
        msg.attach(att)

        # Create a context factory which only allows SSLv3 and does not verify
        # the peer's certificate.
        contextFactory = ClientContextFactory()
        contextFactory.method = SSLv3_METHOD

        d = Deferred()

        mime_obj = StringIO(str(msg))

        senderFactory = ESMTPSenderFactory(
                                           self.username,
                                           self.password,
                                           self.email_address,
                                           self.email_address,
                                           mime_obj,
                                           d,
                                           contextFactory=contextFactory)

        d.addCallback(lambda r: self.email_sent(id, int(self.parts)) )
        d.addErrback(self.email_error)

        reactor.connectTCP(self.smtp_server, self.smtp_port, senderFactory)

        d.addCallback(self.upload_success, *args, **kw)
        d.addErrback(self.upload_error, 1)

        return d


    def upload_success(self, result):
        print "upload was succesful!"

    def upload_error(self, result):
        print "upload error"

    def download_data(self, uid):
        """
        Downloads data from the email server returns a deferred that will return with the data
        """
        print "uid"


if __name__ == "__main__":
    log.startLogging(sys.stdout)
    d = connectToIMAPServer("imap.gmail.com:993", "username", "password")
    def f(s):
        print s


    d.addCallback(lambda r: f("These are fired before the auth and examine callbacks, why?"))
    d.addCallback(lambda r: f("These are fired before the auth and examine callbacks, why?"))
    reactor.run()

该类应该处理登录和选择邮箱，并很好地返回一个可供使用的 IMAP 原型(prototype)，但是底部的两个回调在其他回调之前触发，我明白为什么，回调是在其他回调之前添加的因为 buildProtocol 尚未被调用，所以处理此问题的最佳方法是什么，只需在 init 中添加一个虚拟回调来“保留”第一个位置？

Answer 1

from twisted.internet.endpoints import TCP4ClientEndpoint
d = TCP4ClientEndpoint(reactor, host, int(port)).connect(factory)

和

d.addCallback(lambda r: factory.deferred)    

而不是

d = factory.deferred

在 connectToIMAPServer 中应该这样做 - 只有在协议(protocol)准备好后，您的 factory.deferred 才会返回。 (Twisted Documentation on writing clients)