Question

我是Python的菜鸟，我正在尝试使用telnel.read_all函数捕获设备日志。我正在使用python的日志框架来实现此目的。如果我尝试执行以下操作，代码会挂起： logging.info（telnet.read_all（））

def telNetCallInitial():
 host  = "5.35.8.24"
 user  = "lab"
 password = "lab"
 telnet  = telnetlib.Telnet(host)
 telnet.read_until('Username: ', 3)
 telnet.write(user + '\r')
 telnet.read_until('Password: ', 3)
 telnet.write(password + '\r')
 telnet.write('enable' + '\r\n')
 telnet.write('enable_password' + '\r\n')
 logging.info(telnet.read_all())
 logging.info("inside telnet call initial")
 return telnet

但这不起作用，程序挂起。对此有任何想法。提前谢谢。

Answer 1

您遇到此问题是因为read_all（）是一个阻塞函数调用。也就是说，在telnet连接关闭之前它不会返回（这是一个eof或文件的结尾）。

Python执行从最里面到最外面的函数或方法调用。所以代码如下： logging.info（telnet.read_all（））真的在做： return_value = telnet.read_all（） logging.info（RETURN_VALUE）（return_value只是表示解释器将每次调用的结果传递给它之外的调用）。

对此的解决方案是使用不阻止的调用，可能类似于：

import telnet
import logging
import time

def prepare_connection(host, user, password):
    instance  = telnetlib.Telnet(host)
    instance.read_until('Username: ', 3)
    instance.write(user + '\r')
    instance.read_until('Password: ', 3)
    instance.write(password + '\r')
    instance.write('enable' + '\r\n')
    instance.write('enable_password' + '\r\n')
    # at this point, the connection is prepared so we can return the telnet object
    logging.info("*** Telnet connection prepared")
    return instance

def log_output(telnet_instance):
    """Given a connected telnet instance, sends all data received over it to logging.info."""
    running = True
    while running == True:
        try:
            data = telnet_instance.read_very_eager()
            logging.info(data)
            time.sleep(0.1) # sleep for 100 ms so we don't try too often to read data (read_very_eager won't block,
              # so without this CPU usage would spike)
        except EOFError as e:
            logging.info("*** telnet connection closed")
            running = False

if __name__ == '__main__':
    con = prepare_connection(host="5.35.8.24", user="lab", password="lab")
    log_output(con)

带有telnet read_all函数的python日志框架

1 个答案: