Problems with flask restful and async #30

gcarvellas · 2023-07-29T03:24:17Z

Flask Restful is a python module that allows routes to be formatted in a nice OOP model.

The problem with flask restful is that it does not support async. This is very problematic for performance since our DB and route calls will be blocking.

See if it's possible to add async support. If not, drop flask restful and just use regular blueprints.

gcarvellas · 2023-09-10T23:19:36Z

flask-restful/flask-restful#917 it doesn't seem like async support will be added anytime soon, so flask restful will be removed

gcarvellas · 2023-09-11T03:30:18Z

I ran into an issue where async functions with decorators don't work.

Will go back to this issue at a later point

Error message:

$ curl -X GET -H "Authorization: Bearer $token" -H 'Content-Type: application/json' -d '{"vendorType": "artist"}' localhost:3001/health
<!doctype html>
<html lang=en>
  <head>
    <title>TypeError: The view function did not return a valid response. The return type must be a string, dict, list, tuple with headers or status, Response instance, or WSGI callable, but it was a coroutine.
 // Werkzeug Debugger</title>
    <link rel="stylesheet" href="?__debugger__=yes&amp;cmd=resource&amp;f=style.css">
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  </head>
  <body style="background-color: #fff">
    <div class="debugger">
<h1>TypeError</h1>
<div class="detail">
  <p class="errormsg">TypeError: The view function did not return a valid response. The return type must be a string, dict, list, tuple with headers or status, Response instance, or WSGI callable, but it was a coroutine.
</p>
</div>
<h2 class="traceback">Traceback <em>(most recent call last)</em></h2>
<div class="traceback">
  <h3></h3>
  <ul><li><div class="frame" id="frame-140447334005920">
  <h4>File <cite class="filename">"/usr/local/lib/python3.10/site-packages/flask/app.py"</cite>,
      line <em class="line">2213</em>,
      in <code class="function">__call__</code></h4>
  <div class="source "><pre class="line before"><span class="ws">    </span>def __call__(self, environ: dict, start_response: t.Callable) -&gt; t.Any:</pre>
<pre class="line before"><span class="ws">        </span>&#34;&#34;&#34;The WSGI server calls the Flask application object as the</pre>
<pre class="line before"><span class="ws">        </span>WSGI application. This calls :meth:`wsgi_app`, which can be</pre>
<pre class="line before"><span class="ws">        </span>wrapped to apply middleware.</pre>
<pre class="line before"><span class="ws">        </span>&#34;&#34;&#34;</pre>
<pre class="line current"><span class="ws">        </span>return self.wsgi_app(environ, start_response)</pre></div>
</div>

<li><div class="frame" id="frame-140447334005696">
  <h4>File <cite class="filename">"/usr/local/lib/python3.10/site-packages/flask/app.py"</cite>,
      line <em class="line">2193</em>,
      in <code class="function">wsgi_app</code></h4>
  <div class="source "><pre class="line before"><span class="ws">            </span>try:</pre>
<pre class="line before"><span class="ws">                </span>ctx.push()</pre>
<pre class="line before"><span class="ws">                </span>response = self.full_dispatch_request()</pre>
<pre class="line before"><span class="ws">            </span>except Exception as e:</pre>
<pre class="line before"><span class="ws">                </span>error = e</pre>
<pre class="line current"><span class="ws">                </span>response = self.handle_exception(e)</pre>
<pre class="line after"><span class="ws">            </span>except:  # noqa: B001</pre>
<pre class="line after"><span class="ws">                </span>error = sys.exc_info()[1]</pre>
<pre class="line after"><span class="ws">                </span>raise</pre>
<pre class="line after"><span class="ws">            </span>return response(environ, start_response)</pre>
<pre class="line after"><span class="ws">        </span>finally:</pre></div>
</div>

<li><div class="frame" id="frame-140447334004912">
  <h4>File <cite class="filename">"/usr/local/lib/python3.10/site-packages/flask_cors/extension.py"</cite>,
      line <em class="line">176</em>,
      in <code class="function">wrapped_function</code></h4>
  <div class="source "><pre class="line before"><span class="ws">        </span># Wrap exception handlers with cross_origin</pre>
<pre class="line before"><span class="ws">        </span># These error handlers will still respect the behavior of the route</pre>
<pre class="line before"><span class="ws">        </span>if options.get(&#39;intercept_exceptions&#39;, True):</pre>
<pre class="line before"><span class="ws">            </span>def _after_request_decorator(f):</pre>
<pre class="line before"><span class="ws">                </span>def wrapped_function(*args, **kwargs):</pre>
<pre class="line current"><span class="ws">                    </span>return cors_after_request(app.make_response(f(*args, **kwargs)))</pre>
<pre class="line after"><span class="ws">                </span>return wrapped_function</pre>
<pre class="line after"><span class="ws"></span> </pre>
<pre class="line after"><span class="ws">            </span>if hasattr(app, &#39;handle_exception&#39;):</pre>
<pre class="line after"><span class="ws">                </span>app.handle_exception = _after_request_decorator(</pre>
<pre class="line after"><span class="ws">                    </span>app.handle_exception)</pre></div>
</div>

<li><div class="frame" id="frame-140447334004800">
  <h4>File <cite class="filename">"/usr/local/lib/python3.10/site-packages/flask/app.py"</cite>,
      line <em class="line">2190</em>,
      in <code class="function">wsgi_app</code></h4>
  <div class="source "><pre class="line before"><span class="ws">        </span>ctx = self.request_context(environ)</pre>
<pre class="line before"><span class="ws">        </span>error: BaseException | None = None</pre>
<pre class="line before"><span class="ws">        </span>try:</pre>
<pre class="line before"><span class="ws">            </span>try:</pre>
<pre class="line before"><span class="ws">                </span>ctx.push()</pre>
<pre class="line current"><span class="ws">                </span>response = self.full_dispatch_request()</pre>
<pre class="line after"><span class="ws">            </span>except Exception as e:</pre>
<pre class="line after"><span class="ws">                </span>error = e</pre>
<pre class="line after"><span class="ws">                </span>response = self.handle_exception(e)</pre>
<pre class="line after"><span class="ws">            </span>except:  # noqa: B001</pre>
<pre class="line after"><span class="ws">                </span>error = sys.exc_info()[1]</pre></div>
</div>

<li><div class="frame" id="frame-140447334005024">
  <h4>File <cite class="filename">"/usr/local/lib/python3.10/site-packages/flask/app.py"</cite>,
      line <em class="line">1487</em>,
      in <code class="function">full_dispatch_request</code></h4>
  <div class="source "><pre class="line before"><span class="ws">            </span>rv = self.preprocess_request()</pre>
<pre class="line before"><span class="ws">            </span>if rv is None:</pre>
<pre class="line before"><span class="ws">                </span>rv = self.dispatch_request()</pre>
<pre class="line before"><span class="ws">        </span>except Exception as e:</pre>
<pre class="line before"><span class="ws">            </span>rv = self.handle_user_exception(e)</pre>
<pre class="line current"><span class="ws">        </span>return self.finalize_request(rv)</pre>
<pre class="line after"><span class="ws"></span> </pre>
<pre class="line after"><span class="ws">    </span>def finalize_request(</pre>
<pre class="line after"><span class="ws">        </span>self,</pre>
<pre class="line after"><span class="ws">        </span>rv: ft.ResponseReturnValue | HTTPException,</pre>
<pre class="line after"><span class="ws">        </span>from_error_handler: bool = False,</pre></div>
</div>

<li><div class="frame" id="frame-140447334004464">
  <h4>File <cite class="filename">"/usr/local/lib/python3.10/site-packages/flask/app.py"</cite>,
      line <em class="line">1506</em>,
      in <code class="function">finalize_request</code></h4>
  <div class="source "><pre class="line before"><span class="ws">        </span>with the `from_error_handler` flag.  If enabled, failures in</pre>
<pre class="line before"><span class="ws">        </span>response processing will be logged and otherwise ignored.</pre>
<pre class="line before"><span class="ws"></span> </pre>
<pre class="line before"><span class="ws">        </span>:internal:</pre>
<pre class="line before"><span class="ws">        </span>&#34;&#34;&#34;</pre>
<pre class="line current"><span class="ws">        </span>response = self.make_response(rv)</pre>
<pre class="line after"><span class="ws">        </span>try:</pre>
<pre class="line after"><span class="ws">            </span>response = self.process_response(response)</pre>
<pre class="line after"><span class="ws">            </span>request_finished.send(</pre>
<pre class="line after"><span class="ws">                </span>self, _async_wrapper=self.ensure_sync, response=response</pre>
<pre class="line after"><span class="ws">            </span>)</pre></div>
</div>

<li><div class="frame" id="frame-140447334004576">
  <h4>File <cite class="filename">"/usr/local/lib/python3.10/site-packages/flask/app.py"</cite>,
      line <em class="line">1837</em>,
      in <code class="function">make_response</code></h4>
  <div class="source "><pre class="line before"><span class="ws">                        </span>&#34; dict, list, tuple with headers or status,&#34;</pre>
<pre class="line before"><span class="ws">                        </span>&#34; Response instance, or WSGI callable, but it&#34;</pre>
<pre class="line before"><span class="ws">                        </span>f&#34; was a {type(rv).__name__}.&#34;</pre>
<pre class="line before"><span class="ws">                    </span>).with_traceback(sys.exc_info()[2]) from None</pre>
<pre class="line before"><span class="ws">            </span>else:</pre>
<pre class="line current"><span class="ws">                </span>raise TypeError(</pre>
<pre class="line after"><span class="ws">                    </span>&#34;The view function did not return a valid&#34;</pre>
<pre class="line after"><span class="ws">                    </span>&#34; response. The return type must be a string,&#34;</pre>
<pre class="line after"><span class="ws">                    </span>&#34; dict, list, tuple with headers or status,&#34;</pre>
<pre class="line after"><span class="ws">                    </span>&#34; Response instance, or WSGI callable, but it was a&#34;</pre>
<pre class="line after"><span class="ws">                    </span>f&#34; {type(rv).__name__}.&#34;</pre></div>
</div>
</ul>
  <blockquote>TypeError: The view function did not return a valid response. The return type must be a string, dict, list, tuple with headers or status, Response instance, or WSGI callable, but it was a coroutine.
</blockquote>
</div>

<div class="plain">
    <p>
      This is the Copy/Paste friendly version of the traceback.
    </p>
    <textarea cols="50" rows="10" name="code" readonly>Traceback (most recent call last):
  File &#34;/usr/local/lib/python3.10/site-packages/flask/app.py&#34;, line 2213, in __call__
    return self.wsgi_app(environ, start_response)
  File &#34;/usr/local/lib/python3.10/site-packages/flask/app.py&#34;, line 2193, in wsgi_app
    response = self.handle_exception(e)
  File &#34;/usr/local/lib/python3.10/site-packages/flask_cors/extension.py&#34;, line 176, in wrapped_function
    return cors_after_request(app.make_response(f(*args, **kwargs)))
  File &#34;/usr/local/lib/python3.10/site-packages/flask/app.py&#34;, line 2190, in wsgi_app
    response = self.full_dispatch_request()
  File &#34;/usr/local/lib/python3.10/site-packages/flask/app.py&#34;, line 1487, in full_dispatch_request
    return self.finalize_request(rv)
  File &#34;/usr/local/lib/python3.10/site-packages/flask/app.py&#34;, line 1506, in finalize_request
    response = self.make_response(rv)
  File &#34;/usr/local/lib/python3.10/site-packages/flask/app.py&#34;, line 1837, in make_response
    raise TypeError(
TypeError: The view function did not return a valid response. The return type must be a string, dict, list, tuple with headers or status, Response instance, or WSGI callable, but it was a coroutine.
</textarea>
</div>
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<!--

Traceback (most recent call last):
  File "/usr/local/lib/python3.10/site-packages/flask/app.py", line 2213, in __call__
    return self.wsgi_app(environ, start_response)
  File "/usr/local/lib/python3.10/site-packages/flask/app.py", line 2193, in wsgi_app
    response = self.handle_exception(e)
  File "/usr/local/lib/python3.10/site-packages/flask_cors/extension.py", line 176, in wrapped_function
    return cors_after_request(app.make_response(f(*args, **kwargs)))
  File "/usr/local/lib/python3.10/site-packages/flask/app.py", line 2190, in wsgi_app
    response = self.full_dispatch_request()
  File "/usr/local/lib/python3.10/site-packages/flask/app.py", line 1487, in full_dispatch_request
    return self.finalize_request(rv)
  File "/usr/local/lib/python3.10/site-packages/flask/app.py", line 1506, in finalize_request
    response = self.make_response(rv)
  File "/usr/local/lib/python3.10/site-packages/flask/app.py", line 1837, in make_response
    raise TypeError(
TypeError: The view function did not return a valid response. The return type must be a string, dict, list, tuple with headers or status, Response instance, or WSGI callable, but it was a coroutine.


-->

gcarvellas · 2023-09-14T23:20:17Z

I tried using flask method views to allow us to use async with our OOP controller model. However, according to this page https://flask.palletsprojects.com/en/2.3.x/async-await/ , flask method views don't support async. Thus, the only way for us to have async is to not have our controllers wrapped in classes and use blueprints.

gcarvellas · 2023-09-23T18:30:53Z

moved to #40

gcarvellas added the bug Something isn't working label Jul 29, 2023

gcarvellas self-assigned this Jul 29, 2023

gcarvellas mentioned this issue Sep 23, 2023

Switch from Flask to FastAPI #40

Closed

gcarvellas closed this as completed Sep 23, 2023

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Problems with flask restful and async #30

Problems with flask restful and async #30

gcarvellas commented Jul 29, 2023

gcarvellas commented Sep 10, 2023

gcarvellas commented Sep 11, 2023 •

edited

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gcarvellas commented Sep 14, 2023

gcarvellas commented Sep 23, 2023

Problems with flask restful and async #30

Problems with flask restful and async #30

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gcarvellas commented Jul 29, 2023

gcarvellas commented Sep 10, 2023

gcarvellas commented Sep 11, 2023 • edited Loading

gcarvellas commented Sep 14, 2023

gcarvellas commented Sep 23, 2023

gcarvellas commented Sep 11, 2023 •

edited

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