Lambda控制台捕获非致命异常仍报错，寻求合规日志方案

问题情况 #

在Lambda控制台运行代码时，明明已经捕获了预期的非致命ClientError异常，并且在异常块里加了pass，但还是抛出了KeyError。注释掉异常块里的print语句后问题就消失了，但我想保留调试日志，想问是不是该用logger替代print？

报错详情 #

{"errorMessage": "'message'", "errorType": "KeyError", "requestId": "47445356-38a2-43ec-98f5-2dde22c6af1f", "stackTrace": ["  File \"/var/task/lambda_function.py\", line 11, in lambda_handler\n    dynamodb.pushPriceHistoryToDynamo(str(i.name))\n", "  File \"/opt/python/dynamodbPushData.py\", line 17, in pushPriceHistoryToDynamo\n    response = self.newTable.createPriceHistoryTable(tableName)\n", "  File \"/opt/python/createNewTable.py\", line 37, in createPriceHistoryTable\n    print(f\"[createNewTable]: {err.response['message']} Table already created\")\n"]}

异常处理代码 #

def createPriceHistoryTable(self, tableName: str) -> int:
    try:
        response = self.dynamodb.create_table(
            TableName=tableName,
            KeySchema=[
                {
                    'AttributeName': 'date',
                    'KeyType': 'HASH'  # Hash Key
                }
            ],
            AttributeDefinitions=[
                {
                    'AttributeName': 'date',
                    'AttributeType': 'S'  # string data type
                }
            ],
            ProvisionedThroughput={
                'ReadCapacityUnits': 1,
                'WriteCapacityUnits': 50
            }
        )
        print("[createNewTable]: New table created")
        return 200
    except ClientError  as err:
        if err.response['ResponseMetadata']['HTTPStatusCode'] == 400:
            print(f"[createNewTable]: {err.response['message']} Table already created")
        else:
            print(f"[createNewTable]: {err.response['message']}")
        pass
        return err.response['ResponseMetadata']['HTTPStatusCode']

Lambda主函数代码 #

import json
import dynamodbPushData
import RegionIdEnum
import ItemIdEnum
import time

def lambda_handler(event, context):

    dynamodb = dynamodbPushData.pushData()
    for i in list(ItemIdEnum.item):
        dynamodb.pushPriceHistoryToDynamo(str(i.name))
        # dynamodb.pushItemOrdersToDynamo(str(i.name))


    return {
        'statusCode': 200,
        'body': json.dumps('Hello from Lambda!')
    }

解决办法 #

1. 修复KeyError问题 #

你遇到的KeyError根本原因是**err.response里没有'message'这个键**，AWS SDK返回的错误信息存在err.response['Error']['Message']路径下，或者直接用err.message属性获取更稳妥。修改后的异常块代码如下：

except ClientError as err:
    status_code = err.response['ResponseMetadata']['HTTPStatusCode']
    error_msg = err.response['Error']['Message']
    if status_code == 400:
        print(f"[createNewTable]: {error_msg} Table already created")
    else:
        print(f"[createNewTable]: {error_msg}")
    return status_code

（pass语句在这里没必要，因为后面已经有return逻辑）

2. 日志推荐用logging替代print #

Lambda环境下确实更推荐使用Python的logging模块而非print：

• print的输出会直接混入Lambda的日志流，没有级别区分，不利于后续排查问题
• logging可以设置DEBUG、INFO、ERROR等级别，配合CloudWatch可以更灵活地过滤日志
• 能自动集成Lambda的日志上下文，比如请求ID等信息

示例用法：

import logging

# 初始化logger
logger = logging.getLogger()
logger.setLevel(logging.INFO)

def createPriceHistoryTable(self, tableName: str) -> int:
    try:
        # ... 创建表代码 ...
        logger.info("[createNewTable]: New table created")
        return 200
    except ClientError as err:
        status_code = err.response['ResponseMetadata']['HTTPStatusCode']
        error_msg = err.response['Error']['Message']
        if status_code == 400:
            logger.info(f"[createNewTable]: {error_msg} Table already created")
        else:
            logger.error(f"[createNewTable]: {error_msg}")
        return status_code

内容的提问来源于stack exchange，提问作者Steven