Twisted Producer 延迟写入答案

【问题标题】：Twisted Producer deferred writeTwisted Producer 延迟写入
【发布时间】：2013-02-18 15:45:34
【问题描述】：

在 FTP 服务器示例中，它使用 IWriteFile，它期望消费者我现在拥有的代码缓冲并将 4mb 块发送到服务器，但是生产者写入似乎不期望延迟，但同步写入是安全的使用延迟？

代码

# Deals with giving the FTP Connection a FileConsumer then the File Consumer takes over
class EmailWriter(object):
    implements(IWriteFile)

    def __init__(self, filename):
        print "EmailWriter: %s" % filename
        self.filename = filename
        self._receive = False

    def receive(self):
        assert not self._receive, "Can only call IWriteFile.receive *once* per instance"
        self._receive = True
        # FileConsumer will close the file object
        self.consumer = EmailConsumer("user@gmail.com", "password", "gmail.com", "smtp.gmail.com", 587, self.filename)
        return defer.succeed(self.consumer)

    def close(self):
        # signals that the upload is done
        pass


# Writing Data
class EmailConsumer(object):
    # implements
    # Consumer
    def __init__(self, path, server):
        self.path = path
        self.json_db = JsonDB(path)
        self.server = server

        self.indexes = {}
        self.blocks = 0

        self.start = False
        self.stop = False
        self.producer = None
        self.streaming = None




    def registerProducer(self, producer, streaming):
        # start expecting data
        assert (self.stop == False), "Cannot register multiple times..."
        self.start = True
        self.producer = producer
        self.streaming = streaming


    def unregisterProducer(self):
        # stop expecting data
        self.start = False
        self.stop = True
        self.producer = None
        self.streming = None

    def write(self, bytes):
        # recieve data
        self.buffer += bytes
        if len(self.buffer) > BLOCK_SIZE:
            self.blocks += 1
            d = self.server.send_file(self.buffer)
            d.addCallback(self._done_uploadng, hash(self.buffer), self.blocks)
            self.buffer = ""

    def self._done_uploadng(self, result, hash, block):
        self.index[block] = (hash, self.server.account)
        self.json_db.set_data("index", self.index)

        return result

【问题讨论】：

标签： python asynchronous twisted deferred

【解决方案1】：

简短的回答是肯定的，返回 Deferred 是安全的。

twisted.internet.interfaces.IConsumer 的文档中还有另一个提示：

def write(data):
    """
    The producer will write data by calling this method.

    The implementation must be non-blocking and perform whatever
    buffering is necessary.  If the producer has provided enough data
    for now and it is a L{IPushProducer}, the consumer may call its
    C{pauseProducing} method.
    """

所以我建议您使用 self.producer.pauseProducing() 和 self.producer.resumeProducing() 来包装对 self.server.send_file() 的调用。这样您就不会以可重入的方式调用它，这对于大文件会发生。

【讨论】：