Python3.8 - FastAPI 和无服务器 (AWS Lambda) - 无法处理发送到 api 端点的文件

Question

几个月来，我一直通过 AWS Lambda 函数将 FastAPI 与 Serverless 结合使用，并且效果很好。

我正在创建一个新的 api 端点，它需要发送一个文件。

在我的本地机器上使用时它可以完美运行，但是当我部署到 AWS Lambda 时，当我尝试使用与本地工作完全相同的文件调用我的端点时出现以下错误。我目前正在通过 swagger UI 进行此测试，除了运行代码的“机器”之外，我的无服务器或本地机器之间没有任何变化。

你知道发生了什么吗？

Python 3.8 FastAPI 0.54.1

我的代码：

from fastapi import FastAPI, File, UploadFile
import pandas as pd

app = FastAPI()

@app.post('/process_data_import_quote_file')
def process_data_import_quote_file(file: UploadFile = File(...)): # same error if I put bytes instead of UploadFile
    file = file.file.read()
    print(f"file {file}")
    quote_number = pd.read_excel(file, sheet_name='Data').iloc[:, 0].dropna()

它在最后一行失败

我尝试打印文件，当我将打印的数据与我在本地读取的数据进行比较时，它是不同的。我发誓这是我在 2 上使用的同一个文件，所以我不知道有什么可以解释的？这是一个非常基本的excel文件，没有什么特别之处。

[ERROR] 2020-05-07T14:25:17.878Z    25ff37a5-e313-4db5-8763-1227e8244457    Exception in ASGI application

Traceback (most recent call last):
  File "/var/task/mangum/protocols/http.py", line 39, in run
    await app(self.scope, self.receive, self.send)
  File "/var/task/fastapi/applications.py", line 149, in __call__
    await super().__call__(scope, receive, send)
  File "/var/task/starlette/applications.py", line 102, in __call__
    await self.middleware_stack(scope, receive, send)
  File "/var/task/starlette/middleware/errors.py", line 181, in __call__
    raise exc from None
  File "/var/task/starlette/middleware/errors.py", line 159, in __call__
    await self.app(scope, receive, _send)
  File "/var/task/starlette/exceptions.py", line 82, in __call__
    raise exc from None
  File "/var/task/starlette/exceptions.py", line 71, in __call__
    await self.app(scope, receive, sender)
  File "/var/task/starlette/routing.py", line 550, in __call__
    await route.handle(scope, receive, send)
  File "/var/task/starlette/routing.py", line 227, in handle
    await self.app(scope, receive, send)
  File "/var/task/starlette/routing.py", line 41, in app
    response = await func(request)
  File "/var/task/fastapi/routing.py", line 196, in app
    raw_response = await run_endpoint_function(
  File "/var/task/fastapi/routing.py", line 150, in run_endpoint_function
    return await run_in_threadpool(dependant.call, **values)
  File "/var/task/starlette/concurrency.py", line 34, in run_in_threadpool
    return await loop.run_in_executor(None, func, *args)
  File "/var/lang/lib/python3.8/concurrent/futures/thread.py", line 57, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/var/task/app/quote/processing.py", line 100, in process_data_import_quote_file
    quote_number = pd.read_excel(file, sheet_name='Data').iloc[:, 0].dropna()
  File "/var/task/pandas/io/excel/_base.py", line 304, in read_excel
    io = ExcelFile(io, engine=engine)
  File "/var/task/pandas/io/excel/_base.py", line 821, in __init__
    self._reader = self._engines[engine](self._io)
  File "/var/task/pandas/io/excel/_xlrd.py", line 21, in __init__
    super().__init__(filepath_or_buffer)
  File "/var/task/pandas/io/excel/_base.py", line 355, in __init__
    self.book = self.load_workbook(BytesIO(filepath_or_buffer))
  File "/var/task/pandas/io/excel/_xlrd.py", line 34, in load_workbook
    return open_workbook(file_contents=data)
  File "/var/task/xlrd/__init__.py", line 115, in open_workbook
    zf = zipfile.ZipFile(timemachine.BYTES_IO(file_contents))
  File "/var/lang/lib/python3.8/zipfile.py", line 1269, in __init__
    self._RealGetContents()
  File "/var/lang/lib/python3.8/zipfile.py", line 1354, in _RealGetContents
    fp.seek(self.start_dir, 0)
ValueError: negative seek value -62703616

Answer 1

这是由于 AWS API Gateway。

我不得不继续允许 API Gateway 中的 multipart/form-data 并更正file = BytesIO(file).read()以能够正确使用文件流。