AWS Lambda 未显示 Python 3.8 中的异常堆栈跟踪原因

Question

我使用运行时 Python 3.8 将以下代码部署到 AWS Lambda。

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try:\n    raise Exception(\'my exception\')\nexcept Exception as e:\n    raise ValueError(\'my exception 2\') from e\n

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在 CloudWatch 中，我希望看到像这样的异常链：

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Traceback (most recent call last):\n  File "/var/task/handler.py", line 2, in <module>\n    raise Exception(\'my exception\')\nException: my exception\n\nThe above exception was the direct cause of the following exception:\n\nTraceback (most recent call last):\n  File "/var/task/handler.py", line 4, in <module>\n    raise ValueError(\'my exception 2\') from e\nValueError: my exception 2\n

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相反，我只看到 CloudWatch 中报告的第一个异常，如下所示：

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[ERROR] ValueError: my exception 2\nTraceback (most recent call last):\n\xc2\xa0\xc2\xa0File "/var/task/handler.py", line 21, in pevm_import_budget_file\n\xc2\xa0\xc2\xa0\xc2\xa0\xc2\xa0raise ValueError(\'my exception 2\') from e\n

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为什么日志中没有显示direct cause该语句的异常？from

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Answer 1

你提到的行为是预期的，我也看到过同样的情况。看来 Lambda 目前不支持链式异常。但是，为了解决这个问题，您可以添加自己的记录器来捕获异常。

例如，使用traceback检索异常堆栈：

import traceback

def lambda_handler(event, context):
    try:
        try:
            raise Exception('my exception')
        except Exception as e1:
            raise ValueError('my exception 2')
    except Exception as e2:
        traceback.print_exception(type(e2), value=e2, tb=e2.__traceback__)

    return {}

CloudWatch 日志如下所示：

Traceback (most recent call last):
  File "/var/task/lambda_function.py", line 6, in lambda_handler
    raise Exception('my exception')
Exception: my exception

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/var/task/lambda_function.py", line 8, in lambda_handler
    raise ValueError('my exception 2')
ValueError: my exception 2