Question

您好我在执行一个通过Ubuntu 10服务器执行100mb文件的wget的命令时遇到问题。除此之外，较短的命令工作正常。下面的类包含我如何使用paramiko和我克服这个问题的不同尝试（请参阅不同的run或exec方法）。在exec_cmd的情况下，执行挂起在这一行：

        out = self.in_buffer.read(nbytes, self.timeout)

来自paramiko的channel.py模块的recv方法。

使用Mac中的普通ssh实用程序，相同的wget命令在shell中完美运行。

"""
Management of SSH connections
"""

import logging
import os
import paramiko
import socket
import time
import StringIO


class SSHClient():
    def __init__(self):
        self._ssh_client = paramiko.SSHClient()
        self._ssh_client.load_system_host_keys()
        self._ssh_client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
        self.time_out = 300
        self.wait = 5

    def connect(self, hostname, user, pkey):
        retry = self.time_out
        self.hostname = hostname
        logging.info("connecting to:%s user:%s key:%s" % (hostname, user, pkey))
        while retry > 0:
            try:
                self._ssh_client.connect(hostname,
                                         username=user,
                                         key_filename=os.path.expanduser(pkey),
                                         timeout=self.time_out)
                return
            except socket.error, (value,message):
                if value == 61 or value == 111:
                    logging.warning('SSH Connection refused, will retry in 5 seconds')
                    time.sleep(self.wait)
                    retry -= self.wait
                else:
                    raise
            except paramiko.BadHostKeyException:
                logging.warning("%s has an entry in ~/.ssh/known_hosts and it doesn't match" % self.server.hostname)
                logging.warning('Edit that file to remove the entry and then try again')
                retry = 0
            except EOFError:
                logging.warning('Unexpected Error from SSH Connection, retry in 5 seconds')
                time.sleep(self.wait)
                retry -= self.wait
        logging.error('Could not establish SSH connection')

    def exists(self, path):
        status = self.run('[ -a %s ] || echo "FALSE"' % path)
        if status[1].startswith('FALSE'):
            return 0
        return 1

    def shell(self):
        """
        Start an interactive shell session on the remote host.
        """
        channel = self._ssh_client.invoke_shell()
        interactive_shell(channel)

    def run(self, command):
        """
        Execute a command on the remote host.  Return a tuple containing
        an integer status and a string containing all output from the command.
        """
        logging.info('running:%s on %s' % (command, self.hostname))
        log_fp = StringIO.StringIO()
        status = 0
        try:
            t = self._ssh_client.exec_command(command)
        except paramiko.SSHException:
            logging.error("Error executing command: " + command)
            status = 1
        log_fp.write(t[1].read())
        log_fp.write(t[2].read())
        t[0].close()
        t[1].close()
        t[2].close()
        logging.info('output: %s' % log_fp.getvalue())
        return (status, log_fp.getvalue())

    def run_pty(self, command):
        """
        Execute a command on the remote host with a pseudo-terminal.
        Returns a string containing the output of the command.
        """
        logging.info('running:%s on %s' % (command, self.hostname))
        channel = self._ssh_client.get_transport().open_session()
        channel.get_pty()
        status = 0
        try:
            channel.exec_command(command)
        except:
            logging.error("Error executing command: " + command)
            status = 1
        return status, channel.recv(1024)

    def close(self):
        transport = self._ssh_client.get_transport()
        transport.close()

    def run_remote(self, cmd, check_exit_status=True, verbose=True, use_sudo=False):
        logging.info('running:%s on %s' % (cmd, self.hostname))
        ssh = self._ssh_client
        chan = ssh.get_transport().open_session()
        stdin = chan.makefile('wb')
        stdout = chan.makefile('rb')
        stderr = chan.makefile_stderr('rb')
        processed_cmd = cmd
        if use_sudo:
            processed_cmd = 'sudo -S bash -c "%s"' % cmd.replace('"', '\\"')
        chan.exec_command(processed_cmd)
        result = {
            'stdout': [],
            'stderr': [],
        }
        exit_status = chan.recv_exit_status()
        result['exit_status'] = exit_status

        def print_output():
            for line in stdout:
                result['stdout'].append(line)
                logging.info(line)
            for line in stderr:
                result['stderr'].append(line)
                logging.info(line)
        if verbose:
            print processed_cmd
            print_output()
        return exit_status,result 

    def exec_cmd(self, cmd):
        import select
        ssh = self._ssh_client
        channel = ssh.get_transport().open_session()
        END = "CMD_EPILOGqwkjidksjk58754dskhjdksjKDSL"
        cmd += ";echo " + END
        logging.info('running:%s on %s' % (cmd, self.hostname))
        channel.exec_command(cmd)
        out = ""
        buf = ""
        while END not in buf:
          rl, wl, xl = select.select([channel],[],[],0.0)
          if len(rl) > 0:
              # Must be stdout
              buf = channel.recv(1024)
              logging.info(buf)
              out += buf
        return 0, out

Answer 1

在这种情况下，我会使用列表追加，然后连接。为什么？好吧，字符串在Python中是不可变的。这意味着每次使用+=时，您基本上都会创建两个新字符串并读取第三个字符串。另一方面，如果创建一个列表并附加它，则将创建的字符串数量减半。
你真的需要多次拨打电话吗？我的理解是你并不关心进程是否是线程阻塞的。由于select或多或少是同名C方法的包装器：

select（）和pselect（）允许程序监视多个文件描述符，等待一个或多个文件描述符变为“准备好”某类I / O操作（例如，输入可能）。文件描述符是con 如果可以在不阻塞的情况下执行相应的I / O操作（例如，读取（2）），则备用就绪。
您没有在代码中侦听socket.timeout异常。
写入stdout /文件系统可能很昂贵，但是您要记录recv返回的每一行。你能移动日志线吗？
您是否考虑过手动阅读频道？您技术上唯一需要的代码是：

try:
    out = self.in_buffer.read(nbytes, self.timeout)
except PipeTimeout, e:
    # do something with error

不保证，但会减少额外处理。

Answer 2

我遇到了同样的问题，当我在远程ssh客户端上运行shell脚本时，我的python脚本挂起，在400Mb文件上执行了wget命令。

我发现在wget命令中添加超时可以解决问题。原来我有：

wget http://blah:8888/file.zip

现在用这个：

wget -q -T90 http://blah:8888/file.zip

它就像一个魅力！

希望它有所帮助。

Paramiko在执行大型wget命令时挂起

2 个答案: