问题
I have a code where i am executing a command on remote Linux machine and reading the output using Paramiko. The code def looks like this:
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect(IPAddress, username=user['username'], password=user['password'])
chan = self.ssh.get_transport().open_session()
chan.settimeout(10800)
try:
# Execute thecommand
chan.exec_command(cmd)
contents = StringIO.StringIO()
data = chan.recv(1024)
# Capturing data from chan buffer.
while data:
contents.write(data)
data = chan.recv(1024)
except socket.timeout:
raise socket.timeout
output = contents.getvalue()
return output,chan.recv_stderr(600),chan.recv_exit_status()
The above code works for small outputs, but it gets stuck for larger outputs.
Is there any buffer related issue in here?
回答1:
i see no problem related to stdout channel, but i'm not sure about the way you are handling stderr. Can you confirm, its not the stderr capturing thats causing problem? I'll try out your code and let you know.
Update:
when a command you execute gives lots of messages in STDERR, your code freezes. I'm not sure why, but recv_stderr(600) might be the reason.
So capture error stream the same way you capture standard output.
something like,
contents_err = StringIO.StringIO()
data_err = chan.recv_stderr(1024)
while data_err:
contents_err.write(data_err)
data_err = chan.recv_stderr(1024)
you may even first try and change recv_stderr(600) to recv_stderr(1024) or higher.
回答2:
I am posting the final code which worked with inputs from Bruce Wayne( :) )
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect(IPAddress, username=user['username'], password=user['password'])
chan = self.ssh.get_transport().open_session()
chan.settimeout(10800)
try:
# Execute the given command
chan.exec_command(cmd)
# To capture Data. Need to read the entire buffer to capture output
contents = StringIO.StringIO()
error = StringIO.StringIO()
while not chan.exit_status_ready():
if chan.recv_ready():
data = chan.recv(1024)
#print "Indside stdout"
while data:
contents.write(data)
data = chan.recv(1024)
if chan.recv_stderr_ready():
error_buff = chan.recv_stderr(1024)
while error_buff:
error.write(error_buff)
error_buff = chan.recv_stderr(1024)
exit_status = chan.recv_exit_status()
except socket.timeout:
raise socket.timeout
output = contents.getvalue()
error_value = error.getvalue()
return output, error_value, exit_status
回答3:
Actually I think all above answers can't resolve the real problem:
if the remote program produce large amount of stderr output first then
stdout.readlines()
stderr.readlines()
would hung forever. although
stderr.readlines()
stdout.readlines()
would resolve this case, but it will fail in case the remote program produce large amount of stdout output first.
I don't have a solution yet...
回答4:
It's easier if you use the high level representation of an open ssh session. Since you already use ssh-client to open your channel, you can just run your command from there, and avoid the extra work.
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect(IPAddress, username=user['username'], password=user['password'])
stdin, stdout, stderr = ssh.exec_command(cmd)
for line in stdout.readlines():
print line
for line in stderr.readlines():
print line
You will need to come back and read from these files handles again if you receive additional data afterwards.
回答5:
To have paramiko commands behave like a subprocess.call you may use this piece of code (tested with python-3.5 and paramiko-2.1.1):
#!/usr/bin/env /usr/bin/python3
import os
import sys
from paramiko import SSHClient, AutoAddPolicy
from socket import getfqdn
class SecureSHell(object):
reuser = os.environ['USER']
remote = ''
def __init__(self, *args, **kwargs):
for arg in args:
if hasattr(self, arg):
setattr(self, arg, True)
for (key, val) in kwargs.items():
if hasattr(self, key):
setattr(self, key, val)
@staticmethod
def _ssh_(remote, reuser, port=22):
if '@' in remote:
_reuser, remote = remote.split('@')
_fqdn = getfqdn(remote)
remote = _fqdn if _fqdn else remote
ssh = SSHClient()
ssh.set_missing_host_key_policy(AutoAddPolicy())
ssh.connect(remote, int(port), username=reuser)
return ssh
def call(self, cmd, remote=None, reuser=None):
remote = remote if remote else self.remote
reuser = reuser if reuser else self.reuser
ssh = self._ssh_(remote, reuser)
chn = ssh.get_transport().open_session()
chn.settimeout(10800)
chn.exec_command(cmd)
while not chn.exit_status_ready():
if chn.recv_ready():
och = chn.recv(1024)
while och:
sys.stdout.write(och.decode())
och = chn.recv(1024)
if chn.recv_stderr_ready():
ech = chn.recv_stderr(1024)
while ech:
sys.stderr.write(och.decode())
ech = chn.recv_stderr(1024)
return int(chn.recv_exit_status())
ssh = SecureSHell(remote='example.com', user='d0n')
ssh.call('find')
来源：https://stackoverflow.com/questions/14643861/paramiko-channel-stucks-when-reading-large-ouput