UnleashClient/api/features.py

from typing import Tuple
import requests
from requests.adapters import HTTPAdapter
from urllib3 import Retry

from UnleashClient.constants import REQUEST_TIMEOUT, FEATURES_URL, \
    REQUEST_RETRIES
from UnleashClient.utils import LOGGER, log_resp_info


# pylint: disable=broad-except
def get_feature_toggles(url: str,
                        app_name: str,
                        instance_id: str,
                        custom_headers: dict,
                        custom_options: dict,
                        project: str = None,
                        cached_etag: str = '') -> Tuple[dict, str]:
    """
    Retrieves feature flags from unleash central server.

    Notes:
    * If unsuccessful (i.e. not HTTP status code 200), exception will be caught and logged.
      This is to allow "safe" error handling if unleash server goes down.

    :param url:
    :param app_name:
    :param instance_id:
    :param custom_headers:
    :param custom_options:
    :param project:
    :param cached_etag:
    :return: (Feature flags, etag) if successful, ({},'') if not
    """
    try:
        LOGGER.info("Getting feature flag.")

        headers = {
            "UNLEASH-APPNAME": app_name,
            "UNLEASH-INSTANCEID": instance_id
        }

        if cached_etag:
            headers['If-None-Match'] = cached_etag

        base_url = f"{url}{FEATURES_URL}"
        base_params = {}

        if project:
            base_params = {'project': project}

        adapter = HTTPAdapter(max_retries=Retry(total=REQUEST_RETRIES, status_forcelist=[500, 502, 504]))
        with requests.Session() as session:
            session.mount("https://", adapter)
            session.mount("http://", adapter)
            resp = session.get(base_url,
                               headers={**custom_headers, **headers},
                               params=base_params,
                               timeout=REQUEST_TIMEOUT, **custom_options)

        if resp.status_code not in [200, 304]:
            log_resp_info(resp)
            LOGGER.warning("Unleash Client feature fetch failed due to unexpected HTTP status code.")
            raise Exception("Unleash Client feature fetch failed!")

        etag = ''
        if 'etag' in resp.headers.keys():
            etag = resp.headers['etag']

        if resp.status_code == 304:
            return None, etag

        return resp.json(), etag
    except Exception as exc:
        LOGGER.exception("Unleash Client feature fetch failed due to exception: %s", exc)

    return {}, ''