token_validator giving urllib3 error

[pratibhajagnere]

Hi,

Under normal load, the library works fine but when load increases I start to get below error

File "/usr/local/lib/python3.8/site-packages/django_cognito_jwt/validator.py", line 30, in _json_web_keys
	response = requests.get(self.pool_url + "/.well-known/jwks.json")
File "/usr/local/lib/python3.8/site-packages/requests/api.py", line 75, in get
	return request('get', url, params=params, **kwargs)
File "/usr/local/lib/python3.8/site-packages/requests/api.py", line 60, in request
	return session.request(method=method, url=url, **kwargs)
File "/usr/local/lib/python3.8/site-packages/requests/sessions.py", line 533, in request
	resp = self.send(prep, **send_kwargs)
File "/usr/local/lib/python3.8/site-packages/requests/sessions.py", line 646, in send
	r = adapter.send(request, **kwargs)
File "/usr/local/lib/python3.8/site-packages/requests/adapters.py", line 516, in send
	raise ConnectionError(e, request=request)
requests.exceptions.ConnectionError: HTTPSConnectionPool(host='cognito-idp.xx-xxxx.amazonaws.com', port=443): Max retries exceeded with url: /us-west-2_xxxxxxxxxx/.well-known/jwks.json (Caused by NewConnectionError('<urllib3.connection.VerifiedHTTPSConnection object at 0x7f72c1d67400>: Failed to establish a new connection: [Errno -2] Name does not resolve'))

I propose to initialize the token_validator just once in backend.py like below

class JSONWebTokenAuthentication(BaseAuthentication):
    """Token based authentication using the JSON Web Token standard."""

    token_validator = None

    def authenticate(self, request):
        """Entrypoint for Django Rest Framework"""
        jwt_token = self.get_jwt_token(request)
        if jwt_token is None:
            return None
        if not self.token_validator:
            self.token_validator = self.get_token_validator(request)

        # Authenticate token
        try:
            #token_validator = self.get_token_validator(request)
            jwt_payload = self.token_validator.validate(jwt_token)
        except TokenError as e:
            raise exceptions.AuthenticationFailed()