I am writing a REST API GET endpoint that needs to both return a response and store records to either GCP Cloud SQL (MySQL), but I want the return to not be dependent on completion of the writing of the records. Basically, my code will look like:

def predict():
    req = request.json.get("instances")
    resp = make_response(req)
    write_to_bq(req)
    write_to_bq(resp)
    return resp

Is there any easy way to do this with Cloud SQL Client Library or something?

CodePudding user response：

Turns our flask has a functionality that does what I require:

@app.route("predict", method=["GET"]):
def predict():
    # do some stuff with the request.json object
    return jsonify(response)

@app.after_request
def after_request_func(response):
    # do anything you want that relies on context of predict()
    @response.call_on_close
    def persist():
        # this will happen after response is sent,
        # so even if this function fails, the predict()
        # will still get it's response out
        write_to_db()
    return response

One important thing is that a method tagged with after_request must take an argument and return something of type flask.Response. Also I think if method has call_on_close tag, you cannot access from context of main method, so you need to define anything you want to use from the main method inside the after_request tagged method but outside (above) the call_on_close method.