Injecting a Flask Request into another Flask App

Question

Is there a way to inject a Flask request object into a different Flask app. This is what I'm trying to do:

app = flask.Flask(__name__)

@app.route('/foo/<id>')
def do_something(id):
  return _process_request(id)

def say_hello(request):
   # request is an instance of flask.Request.
   # I want to inject it into 'app'

I'm trying this with Google Cloud Functions, where say_hello() is a function that is invoked by the cloud runtime. It receives a flask.Request as the argument, which I want to then process through my own set of routes.

I tried the following, which doesn't work:

def say_hello(request):
    with app.request_context(request.environ):
        return app.full_dispatch_request()

This responds with 404 errors for all requests.

Edit:

The simple way to implement say_hello() is as follows:

def say_hello(request):
    if request.method == 'GET' and request.path.startswith('/foo/'):
        return do_something(_get_id(request.path))
    flask.abort(404)

This essentially requires me to write the route matching logic myself. I'm wondering if there's a way to avoid doing that, and instead use Flask's built-in decorators and routing capabilities.

Edit 2:

Interestingly, dispatching across apps work locally:

app = flask.Flask(__name__)

# Add app.routes here

functions = flask.Flask('functions')

@functions.route('/', defaults={'path': ''})
@functions.route('/<path:path>', methods=['GET', 'POST', 'PUT', 'DELETE'])
def catch_all(path):
    with app.request_context(flask.request.environ):
        return app.full_dispatch_request()

if __name__ == '__main__':
    functions.run()

But the same technique doesn't seem to work on GCF.

you mean multiple instances of an app? other than that, you might be able to get away with requests and actually making a request to a view of the other app you have. — senaps
Not quite sure I follow you. I added some more details to the post, further explaining what I'm attempting to do. — Hiranya Jayathilaka

Dustin Ingram Dustin Ingram · Accepted Answer · 2018-08-24T21:15:48

I wouldn't recommend this method, but this is technically possible by abusing the request stack and rewriting the current request and re-dispatching it.

However, you'll still need to do some type of custom "routing" to properly set the url_rule, as the incoming request from GCF won't have it (unless you explicitly provide it via the request):

from flask import Flask, _request_ctx_stack
from werkzeug.routing import Rule

app = Flask(__name__)

@app.route('/hi')
def hi(*args, **kwargs):
    return 'Hi!'

def say_hello(request):
    ctx = _request_ctx_stack.top
    request = ctx.request
    request.url_rule = Rule('/hi', endpoint='hi')
    ctx.request = request
    _request_ctx_stack.push(ctx)
    return app.dispatch_request()

Injecting a Flask Request into another Flask App

1 Answers