Python日志代码导致类运行终止，请求排查原因

以下代码导致我的Netweb类无法运行，我推测问题出在logger.FileHandler模块，但相同代码在其他脚本里能正常执行。已经确认文件路径存在，且IIS服务器用户有写入权限。日志通过logger.info(f'get_vlans({ip_address}, {int_len}, {type})')调用，所有传入变量值都验证正确。

日志代码 #

import logging
import datetime

now = datetime.datetime.now()
now = now.strftime("%m-%Y")

# create logger with the name 'gp_uccx_app'
logger = logging.getLogger('netweb_logger')
logger.setLevel(logging.DEBUG)

# # create file handler
fh = logging.FileHandler(f'C:/inetpub/wwwroot/site1/python/custom/logs/log-{now}.txt')
fh.setLevel(logging.DEBUG)

# create formatter and add it to the handler
formatter = logging.Formatter(
    '%(asctime)s - %(name)s - %(levelname)s - %(message)s'
)
fh.setFormatter(formatter)

# add the handler to the logger
logger.addHandler(fh)

Netweb类代码 #

class Netweb:


# Collects the vlans for all interfaces in the stack that have the line 'switchport access vlan' in the running config
def get_vlans(ip_address, int_len, type):
    logger.info(f'get_vlans({ip_address}, {int_len}, {type})')
    vlans = []
    try:
        reSearch = ''
        if int_len == 'long' and type == 'gigabitethernet':
            reSearch = "^interface GigabitEthernet\d\/0\/\d"
        elif int_len == 'long' and type == 'fastethernet':
            reSearch = "^interface FastEthernet\d\/\d"
        elif int_len == 'short' and type == 'gigabitethernet':
            reSearch = "^interface GigabitEthernet\d\/\d"
        elif int_len == 'short' and type == 'fastethernet':
            reSearch = "^interface FastEthernet\d\/\d"
        net_connect = ConnectHandler( device_type=platform, ip=ip_address, username=cisco_username, password=cisco_password )

        output = net_connect.send_command( 'show run | i (interface)|.(access vlan)' )
        net_connect.disconnect()

        output = output.splitlines()

        x = 0

        for out in output:
            if re.search( reSearch, out ):
                interface = out.split()
                interface = interface[ 1 ]
                if 'access vlan' in output[ x + 1 ]:
                    vlan = output[ x + 1 ].split( 'switchport access vlan' )[1].strip()
                else:
                    vlan = '1'
                vlans.append( [ interface, vlan ] )

            x = x + 1
            
        return vlans
    except Exception as e:
        logger.info(e)

排查方向 #

• 类方法定义错误：get_vlans是Netweb类中的方法，但未添加self参数，也没有@staticmethod装饰器。如果是实例方法，第一个参数必须是self；如果不需要实例化调用，要加上@staticmethod，否则调用时会抛出参数不匹配的异常。这很可能是类无法运行的核心原因。
• 日志处理器重复添加：若日志模块被多次导入，会重复给netweb_logger添加FileHandler，引发文件占用或写入失败。可以在添加处理器前做判断：

  if not logger.hasHandlers():
      fh = logging.FileHandler(f'C:/inetpub/wwwroot/site1/python/custom/logs/log-{now}.txt')
      # 后续设置格式、添加处理器的代码
  

• 未导入依赖模块/变量：Netweb类中用到的re、ConnectHandler、platform、cisco_username、cisco_password均未在代码中体现导入或定义，这些未定义项会直接抛出异常。如果日志初始化失败，异常信息无法被记录，会误导你认为是日志模块的问题。
• IIS权限验证：虽然确认了写入权限，但需验证IIS应用池身份是否真的拥有该路径的创建、修改文件权限。可以用该身份手动执行一个简单的文件写入脚本，比如：

  with open('C:/inetpub/wwwroot/site1/python/custom/logs/test.txt', 'w') as f:
      f.write('test')
  

  看是否能成功写入。
• 异常日志降级排查：如果怀疑日志模块有问题，可在get_vlans的异常块中添加基础文件写入，绕过日志模块直接记录异常：

  except Exception as e:
      with open('C:/inetpub/wwwroot/site1/python/custom/logs/error.txt', 'a') as f:
          f.write(f'{datetime.datetime.now()}: {str(e)}\n')
  

  以此确认到底是日志模块的问题，还是其他代码逻辑的问题。

内容的提问来源于stack exchange，提问作者Blinkydamo