Check app status in servers and add/remove accordingly

a_checks.py

import sys 
import argparse
import redis
import json
import requests


def parse_arguments():
    parser = argparse.ArgumentParser(description='')
    parser.add_argument(
        "-c", "--config", dest="config", default='config.json', 
        help="Configuration file"
    )   
    
    return parser.parse_args()


def get_config(config_file):
    try:
        with open(config_file) as f:
            config = json.loads(f.read())
    except (IOError, json.decoder.JSONDecodeError) as e:
        print("[%s]: %s" % (e.__class__.__name__, e)) 
        sys.exit(1)

    return config


def redis_connect(config):
    host = config['redis']['host']
    port = config['redis']['port']
    db = config['redis']['db']
    pwd = config['redis']['password']

    return redis.StrictRedis(host=host, port=port, db=db, password=pwd)

def exclude_host(_redis, host):
    print("Removing host %s from cluster" % host)

    # TODO: Remove DNS entry in case of DNS RR.
    
    # Add in failed set into redis
    _redis.sadd('failed', host)
    return True


def include_host(_redis, host):
    print("Including host %s to cluster again" % host)

    # TODO: Add DNS entry back in case of DNS RR.

    # Remove from failed set into redis
    _redis.srem('failed', host)
    return True


def do_checks(_redis, config):
    hosts = config['hosts']
    for host in hosts:
        # check API
        headers = {'Host': config['app']['domain_api']}
        url = 'http://' + host + '/api'
        try:
            response = requests.get(url, headers=headers)
        except requests.exceptions.ConnectionError as e:
            print(e)
            sys.exit(1)

        if response.status_code == 200:
            _redis.lpush(host, 0)
        else:
            _redis.lpush(host, 1)

        # trim to last N checks
        number_checks = int(config['number_checks'])
        _redis.ltrim(host, 0, number_checks - 1)

        # get last N checks
        checks = _redis.lrange(host, 0, -1)
        checks = [ int(e) for e in checks ]

        if response.status_code != 200:
            if _redis.sismember('failed', host):
                continue
            if sum(checks) == number_checks:
                exclude_host(_redis, host)
        else:
            if _redis.sismember('failed', host):
                if sum(checks) == 0:
                    include_host(_redis, host)


def main():
    args = parse_arguments()
    config = get_config(args.config)
    _redis = redis_connect(config)
    do_checks(_redis, config)


if __name__ == '__main__':
    main()

config.json

{
  "redis": {
    "host": "127.0.0.1",
    "port": 6379,
    "db": 0,
    "password": ""
  },  
  "number_checks": 5,
  "hosts": ["fe.domain.tld", "fe2.domain.tld"],
  "app": {
    "domain_api": "app-api.domain.tld"
  }
}