通过 Python ftplib 传输文件不确定超时

Question

我正在尝试使用 ftplib 将一组文件从我的计算机（运行 64 位 Windows 7）传输到 Linux 服务器。过程类似于这个测试代码的sn-p（服务器地址，用户名和密码显然改变了）：

import ftplib
import os.path
import os

host     = "some.ftp.server.com"
username = "username"
password = "password"

outDir = "/some/output/directory"

def transfer_files():
    ftp = ftplib.FTP(host, username, password)

    ftp.cwd(outDir)
    names = ftp.nlst()
    if "transferred" not in names:
        ftp.mkd("transferred")
    ftp.cwd("transferred")
    names = ftp.nlst()

    # Transfrer arbitrary files to the server
    filesToTransfer = os.listdir('.')
    for fName in filesToTransfer:
        if not os.path.isfile(fName):
            continue
        if fName in names:
            ftp.delete(fName)
        with open(fName, 'r') as f:
            ftp.storbinary("STOR %s" % fName, f)
        print fName

    ftp.quit()

    print "Done"

if __name__ == "__main__":
    transfer_files()

我看到的行为是大多数文件传输快速且成功，但随机文件会超时并引发以下异常：

Traceback (most recent call last):
  File "Test.py", line 37, in <module>
    transfer_files()
  File "Test.py", line 29, in transfer_files
    ftp.storbinary("STOR %s" % base, f)
  File "C:\Python27\Lib\ftplib.py", line 471, in storbinary
    conn = self.transfercmd(cmd, rest)
  File "C:\Python27\Lib\ftplib.py", line 376, in transfercmd
    return self.ntransfercmd(cmd, rest)[0]
  File "C:\Python27\Lib\ftplib.py", line 335, in ntransfercmd
    conn = socket.create_connection((host, port), self.timeout)
  File "C:\Python27\Lib\socket.py", line 575, in create_connection
    raise err
socket.error: [Errno 10060] A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond

每次运行程序时超时的文件都不一样，但似乎总是发生在一个文件或另一个文件上。为什么传输会随机超时，我该怎么做才能防止这种情况发生？

Answer 1

在批量处理网络请求时，出现一定数量的超时是完全正常的，甚至是意料之中的。与其试图阻止超时发生（因为它们总是会发生），不如向应用程序添加逻辑以处理发生超时的情况。由于您正在批量上传文件，因此在引发异常时可能看起来像是重新尝试上传。