serve_http.py

"""
Script for serving.
"""
import json
import pickle

import numpy as np
from boxkite.monitoring.service import ModelMonitoringService
from flask import Flask, Response, current_app, request

from utils.constants import AREA_CODES, STATES, SUBSCRIBER_FEATURES

OUTPUT_MODEL_NAME = "/artefact/lgb_model.pkl"


def predict_prob(subscriber_features,
                 model=pickle.load(open(OUTPUT_MODEL_NAME, "rb"))):
    """Predict churn probability given subscriber_features.

    Args:
        subscriber_features (dict)
        model

    Returns:
        churn_prob (float): churn probability
    """
    row_feats = list()
    for col in SUBSCRIBER_FEATURES:
        row_feats.append(subscriber_features[col])

    for area_code in AREA_CODES:
        if subscriber_features["Area_Code"] == area_code:
            row_feats.append(1)
        else:
            row_feats.append(0)

    for state in STATES:
        if subscriber_features["State"] == state:
            row_feats.append(1)
        else:
            row_feats.append(0)

    # Score
    churn_prob = (
        model
        .predict_proba(np.array(row_feats).reshape(1, -1))[:, 1]
        .item()
    )

    # Log the prediction
    current_app.monitor.log_prediction(
        request_body=json.dumps(subscriber_features),
        features=row_feats,
        output=churn_prob
    )

    return churn_prob


# pylint: disable=invalid-name
app = Flask(__name__)


@app.route("/", methods=["POST"])
def get_churn():
    """Returns the `churn_prob` given the subscriber features"""

    subscriber_features = request.json
    result = {
        "churn_prob": predict_prob(subscriber_features)
    }
    return result


@app.before_first_request
def init_background_threads():
    """Global objects with daemon threads will be stopped by gunicorn --preload flag.
    So instantiate them here instead.
    """
    current_app.monitor = ModelMonitoringService()


@app.route("/metrics", methods=["GET"])
def get_metrics():
    """Returns real time feature values recorded by prometheus
    """
    body, content_type = current_app.monitor.export_http(
        params=request.args.to_dict(flat=False),
        headers=request.headers,
    )
    return Response(body, content_type=content_type)


def main():
    """Starts the Http server"""
    app.run()


if __name__ == "__main__":
    main()