Running In Serverless Lambda Using serverless-wsgi

[AhmedNourJamalElDin]

Hello,
Is there a way to use this package without app.run() where serverless doesnt require running the app using the aforementioned command?

When using this package, for some reason I can't use "contructor injection", nor injector.get(INTERFACE) but this works:

flask_injector = FlaskInjector(app, modules=modules)

# some code
# some other code
# also some other code

flask_injector.get(INTERFACE)

Thanks :D

[jstasiak]

I'm not entirely sure what this question is about. It'd help if you could provide

• a minimal, complete piece of code to reproduce the issue
• the interaction with the piece of code (the way you run it etc.) to reproduce the issue
• what the issue is (stack trace)
• the versions of the software you're running (Python, Flask, Flask-Injector, injector)

[AhmedNourJamalElDin]

• a minimal, complete piece of code to reproduce the issue

init_app.py

from flask import Flask
from flask_restful import Api
from flask_injector import FlaskInjector
from injector import Module, singleton, provider

app = Flask(__name__)
api = Api(app)

class InjectorModule(Module):
    @singleton
    @provider
    def provide_email_client(self) -> EmailClient:
        return SesClient(some_region)

flask_injector = FlaskInjector(app=app, modules=[InjectorModule])

from src.resources import *
app.register_blueprint(routes)

app.app_context().push()

some resource file

class SomeResource(Resource):
    @inject
    def __init__(self, email_client: EmailClient):
          self.email_client = email_client

    def post(self):
        # some code using self.email_client

• what the issue is (stack trace)

the exception:

TypeError: __init__() missing 1 required positional argument: 'email_client'

Stacktrace:

Traceback (most recent call last):
  File "/home/anjd/.local/share/virtualenvs/nfx-ares-0nfxTZOd/lib/python3.7/site-packages/flask/app.py", line 2463, in __call__
    return self.wsgi_app(environ, start_response)
  File "/home/anjd/.local/share/virtualenvs/nfx-ares-0nfxTZOd/lib/python3.7/site-packages/flask/app.py", line 2449, in wsgi_app
    response = self.handle_exception(e)
  File "/home/anjd/.local/share/virtualenvs/nfx-ares-0nfxTZOd/lib/python3.7/site-packages/flask_restful/__init__.py", line 269, in error_router
    return original_handler(e)
  File "/home/anjd/.local/share/virtualenvs/nfx-ares-0nfxTZOd/lib/python3.7/site-packages/flask_cors/extension.py", line 161, in wrapped_function
    return cors_after_request(app.make_response(f(*args, **kwargs)))
  File "/home/anjd/.local/share/virtualenvs/nfx-ares-0nfxTZOd/lib/python3.7/site-packages/flask/app.py", line 1866, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/home/anjd/.local/share/virtualenvs/nfx-ares-0nfxTZOd/lib/python3.7/site-packages/flask/_compat.py", line 38, in reraise
    raise value.with_traceback(tb)
  File "/home/anjd/.local/share/virtualenvs/nfx-ares-0nfxTZOd/lib/python3.7/site-packages/flask/app.py", line 2446, in wsgi_app
    response = self.full_dispatch_request()
  File "/home/anjd/.local/share/virtualenvs/nfx-ares-0nfxTZOd/lib/python3.7/site-packages/flask/app.py", line 1951, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/home/anjd/.local/share/virtualenvs/nfx-ares-0nfxTZOd/lib/python3.7/site-packages/flask_restful/__init__.py", line 269, in error_router
    return original_handler(e)
  File "/home/anjd/.local/share/virtualenvs/nfx-ares-0nfxTZOd/lib/python3.7/site-packages/flask_cors/extension.py", line 161, in wrapped_function
    return cors_after_request(app.make_response(f(*args, **kwargs)))
  File "/home/anjd/.local/share/virtualenvs/nfx-ares-0nfxTZOd/lib/python3.7/site-packages/flask/app.py", line 1820, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/home/anjd/.local/share/virtualenvs/nfx-ares-0nfxTZOd/lib/python3.7/site-packages/flask/_compat.py", line 38, in reraise
    raise value.with_traceback(tb)
  File "/home/anjd/.local/share/virtualenvs/nfx-ares-0nfxTZOd/lib/python3.7/site-packages/flask/app.py", line 1949, in full_dispatch_request
    rv = self.dispatch_request()
  File "/home/anjd/.local/share/virtualenvs/nfx-ares-0nfxTZOd/lib/python3.7/site-packages/flask/app.py", line 1935, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/home/anjd/.local/share/virtualenvs/nfx-ares-0nfxTZOd/lib/python3.7/site-packages/flask_restful/__init__.py", line 458, in wrapper
    resp = resource(*args, **kwargs)
  File "/home/anjd/.local/share/virtualenvs/nfx-ares-0nfxTZOd/lib/python3.7/site-packages/flask/views.py", line 88, in view
    self = view.view_class(*class_args, **class_kwargs)
TypeError: __init__() missing 1 required positional argument: 'email_client'

• the versions of the software you're running (Python, Flask, Flask-Injector, injector)

Python: 3.7
Flask: 1.1.1 and 1.0.2
Flask-RESTful: 0.3.7
injector: 0.18.3
Flask-Injector: 0.12.3

Anything else? :D

TBH the code doesn't run app.run() at all because, you know, it's AWS Lambda, which acts like a normal python function which takes two arguments: event and context. Some wrappers are there to integrate AWS Lambda with WSGI hence it works with Flask, and one of them is serverless-wsgi which I use.

[jstasiak]

app.run() shouldn't matter, Flask-Injector doesn't need it per se. I don't really know AWS Lambda, but what stands out from your example (which still seems incomplete so I can't run it) is this part:

flask_injector = FlaskInjector(app=app, modules=[InjectorModule])

from src.resources import *
app.register_blueprint(routes)

Registering all views (even those owned by blueprints) needs to happen before FlaskInjector instance is created, otherwise they're not gonna be injected into.

[AhmedNourJamalElDin]

Hollllllllllllllly :D

My bad, this solved my problem.

Thanks soooooooooooooooooo much <3

[jstasiak]

No worries, good to hear it's working for you now. Also this should be documented better I think :)