Flask结合Firebase Cloud Function访问request.json时出现超时循环问题

问题现象 #

用Flask结合Google Cloud Functions开发JSON API时，POST请求到/events端点后，控制台显示Flask已返回<Response 41 bytes [201 CREATED]>响应，但Cloud Functions却触发60秒超时，最终抛出ClientDisconnected异常。尝试用request.get_data(as_text=True)替代request.json后问题依旧。

原代码示例 #

@app.route("/events",methods=['POST'])
def post_event():
    # new_event = request.get_data(as_text=True)
    new_event = request.json
    print(new_event)
    return {"message":"Event created successfully"}, 201

# Expose Flask app as a single Cloud Function:

@https_fn.on_request(max_instances=10)
def httpsflaskexample(req: https_fn.Request) -> https_fn.Response:
    with app.request_context(req.environ):
        flask_response = app.full_dispatch_request()
        print(flask_response)
        return flask_response

控制台输出 #

>  WARNING: This is a development server. Do not use it in a production deployment. Use a production WSGI server instead.
>   * Running on http://127.0.0.1:8374
>  Press CTRL+C to quit
>  <Response streamed [404 NOT FOUND]>
>  127.0.0.1 - - [24/Sep/2023 20:51:58] "GET /__/health HTTP/1.1" 404 -
i  functions: Beginning execution of "us-central1-httpsflaskexample"
>  {'name': 'Add your name in the body'}
>  <Response 41 bytes [201 CREATED]>

(*疑似无限循环或异常情况发生)

超时错误日志 #

i  Your function timed out after ~60s. To configure this timeout, see
      https://firebase.google.com/docs/functions/manage-functions#set_timeout_and_memory_allocation.
i  Request to function failed: Error: socket hang up
>  [2023-09-24 20:52:58,110] ERROR in app: Exception on /events [POST]
>  Traceback (most recent call last):
>    File "...\functions\venv\lib\site-packages\flask\app.py", line 2190, in wsgi_app
>      response = self.full_dispatch_request()
>    File "...\functions\venv\lib\site-packages\flask\app.py", line 1487, in full_dispatch_request
>      return self.finalize_request(rv)
>    File "...\functions\venv\lib\site-packages\flask\app.py", line 1508, in finalize_request
>      response = self.process_response(response)
>    File "...\functions\venv\lib\site-packages\flask\app.py", line 2002, in process_response
>      response = self.ensure_sync(func)(response)
>    File "...\functions\venv\lib\site-packages\functions_framework\__init__.py", line 302, in read_request
>      flask.request.get_data()
>    File "...\functions\venv\lib\site-packages\werkzeug\wrappers\request.py", line 423, in get_data
>      rv = self.stream.read()
>    File "...\functions\venv\lib\site-packages\werkzeug\wsgi.py", line 829, in readall
>      data = self.read(1024 * 64)
>    File "...\functions\venv\lib\site-packages\werkzeug\wsgi.py", line 814, in readinto
>      self.on_disconnect()
>    File "...\functions\venv\lib\site-packages\werkzeug\wsgi.py", line 751, in on_disconnect
>      raise ClientDisconnected()
>  werkzeug.exceptions.ClientDisconnected: 400 Bad Request: The browser (or proxy) sent a request that this server could not understand.

解决方法 #

问题根源是直接将Flask的Response对象返回给Cloud Functions，两者响应处理机制不兼容，导致请求流读取异常。需提取Flask响应的内容、状态码和头部，构建成Cloud Functions兼容的https_fn.Response对象返回。

修改后的入口函数代码：

@https_fn.on_request(max_instances=10)
def httpsflaskexample(req: https_fn.Request) -> https_fn.Response:
    with app.request_context(req.environ):
        flask_response = app.full_dispatch_request()
        print(flask_response)
        # 转换为Cloud Functions兼容的响应格式
        return https_fn.Response(
            response=flask_response.get_data(),
            status=flask_response.status_code,
            headers=dict(flask_response.headers)
        )

关键说明 #

• flask_response.get_data()：读取Flask响应的原始字节内容
• flask_response.status_code：获取响应状态码
• dict(flask_response.headers)：将Flask响应头部转为字典，适配Cloud Functions的Response要求

修改后即可避免超时和ClientDisconnected异常。

内容的提问来源于stack exchange，提问作者Kevin Cespedes Arancibia