falcon_gateway.py

# falcon_gateway.py
import falcon
import os
import json
import pickle
from data_handler import invoke_predict

# Falcon follows the REST architectural style, meaning (among
# other things) that you think in terms of resources and state
# transitions, which map to HTTP verbs.

class InfoResource(object):
    def on_get(self, req, resp):
        """Handles GET requests"""
        resp.status = falcon.HTTP_200  # This is the default status
        resp.body = ('\nThis is an API for a deployed Datmo model, '
                     'where it takes flower lengths as input and returns the predicted Iris species.\n'
                     'To learn more about this model, send a GET request to the /predicts endpoint or visit the repository online at: \n\n'
                     'https://datmo.com/nmwalsh/falcon-api-model\n\n')


class PredictsResource(object):
    def on_get(self, req, resp):
        """Handles GET requests"""
        resp.status = falcon.HTTP_200  # This is the default status
        resp.body = ('\nThis is the PREDICT endpoint. \n'
        			 'Both requests and responses are served in JSON. \n'
        		     '\n'
        		     'INPUT:  Flower Lengths (in cm) \n'
                     '   "sepal_length":[num]        \n'
                     '   "sepal_width": [num]        \n'
                     '   "petal_length":[num]        \n'
                     '   "petal_width": [num]      \n\n'
        		     'OUTPUT: Prediction (Species)   \n'
                     '   "Species": [string]       \n\n')

    def on_post(self, req, resp): 
        """Handles POST requests"""
        try:
            raw_json = req.stream.read()
        except Exception as ex:
            raise falcon.HTTPError(falcon.HTTP_400,
                'Error',
                ex.message)
 
        try:
            result_json = json.loads(raw_json.decode(), encoding='utf-8')
            # For Python 2.x, replace with
            # result_json = json.loads(raw_json, encoding='utf-8')
        except ValueError:
            raise falcon.HTTPError(falcon.HTTP_400,
                'Malformed JSON',
                'Could not decode the request body. The '
                'JSON was incorrect.')
        
        # loading model file
        model_filename = os.path.join('model.dat')
        model = pickle.load(open(model_filename, 'rb'))

        resp.status = falcon.HTTP_200
        resp.body = json.dumps(invoke_predict(model, raw_json))  
        # For Python 2.x, replace with
        # resp.body = json.dumps(invoke_predict(model, raw_json), encoding='utf-8') encoding not necessary in python3.
         

# falcon.API instances are callable WSGI apps. Never change this.
app = falcon.API()

# Resources are represented by long-lived class instances. Each Python class becomes a different "URL directory"
info = InfoResource()
predicts = PredictsResource()
# things will handle all requests to the '/things' URL path
app.add_route('/info', info)
app.add_route('/predicts', predicts)