What is the difference between calling open_sftp() locally and via a separate function?

问题

In the following code, the first test passes, and the second one does not, which I find puzzling.

import paramiko

def test1():
    client = paramiko.SSHClient()
    client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
    client.connect('10.0.0.107', username='test', password='test')
    sftp = client.open_sftp()
    sftp.stat('/tmp')
    sftp.close()

def get_sftp():
    client = paramiko.SSHClient()
    client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
    client.connect('10.0.0.107', username='test', password='test')
    return client.open_sftp()

def test2():
    sftp = get_sftp()
    sftp.stat('/tmp')
    sftp.close()

if __name__ == '__main__':
    test1()
    print 'test1 done'
    test2()
    print 'test2 done'

Here's what I get:

$ ./script.py
test1 done
Traceback (most recent call last):
  File "./play.py", line 25, in <module>
    test2()
  File "./play.py", line 20, in test2
    sftp.stat('/tmp')
  File "/usr/lib/pymodules/python2.6/paramiko/sftp_client.py", line 337, in stat
    t, msg = self._request(CMD_STAT, path)
  File "/usr/lib/pymodules/python2.6/paramiko/sftp_client.py", line 627, in _request
    num = self._async_request(type(None), t, *arg)
  File "/usr/lib/pymodules/python2.6/paramiko/sftp_client.py", line 649, in _async_request
    self._send_packet(t, str(msg))
  File "/usr/lib/pymodules/python2.6/paramiko/sftp.py", line 172, in _send_packet
    self._write_all(out)
  File "/usr/lib/pymodules/python2.6/paramiko/sftp.py", line 138, in _write_all
    raise EOFError()
EOFError

This happens both on Ubuntu (Python 2.6 and paramiko 1.7.6) and Debian (Python 2.7 and paramiko 1.7.7).

If I run test2 first, I only get the stack trace, meaning test2 indeed fails.

回答1:

Ok, I've verified it on debian/python2.6/paramiko1.7.6.

The reason is that the client object goes out of scope in get_sftp (and closes the "channel"). If you cange it so you return the client:

import paramiko

def get_sftp():
    client = paramiko.SSHClient()
    client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
    client.connect('localhost', username='root', password='B4nan-purr(en)')
    return client

def test2():
    client = get_sftp()
    sftp = client.open_sftp()
    sftp.stat('/tmp')
    sftp.close()


if __name__ == "__main__":
    test2()

then everything will work (the function name should probably be changed..).

来源：https://stackoverflow.com/questions/11925895/what-is-the-difference-between-calling-open-sftp-locally-and-via-a-separate-fu

标签

python

paramiko