main.py

import os
import logging
from time import sleep
from redis import Sentinel
from kubernetes import client, config

logging.basicConfig(
    level=logging.INFO, 
)

SENTINEL_NAME = os.getenv('SENTINEL_NAME', 'localhost')
SENTINEL_PORT = int(os.getenv('SENTINEL_PORT', 26379))
MASTER_SET_NAME = os.getenv('MASTER_SET_NAME', 'mymaster')
NAMESPACE = os.getenv('NAMESPACE', 'default')
SERVICE_NAME = os.getenv('SERVICE_NAME', 'redis-bitnami-master')
KUBECONFIG = os.getenv('KUBECONFIG', '/code/config/kubeconfig')
SLEEP_TIME = int(os.getenv('SLEEP_TIME', 10))

logging.info('Load kube config')
config.load_incluster_config()
v1 = client.CoreV1Api()

external_name = ""

def main():
    while True:
        sentinel = Sentinel([(SENTINEL_NAME, SENTINEL_PORT)], socket_timeout=0.5)
        try:
            redis_master_name = sentinel.discover_master(MASTER_SET_NAME)[0]
        except Exception as e:
            logging.exception(e)
            sleep(1)
            continue

        service_exist = False

        try:
            service = v1.read_namespaced_service(name = SERVICE_NAME, namespace = NAMESPACE)
            external_name = service.spec.external_name
            service_exist = True
        except Exception as e:
            logging.exception(e)

        service_metadata = client.V1ObjectMeta(name=SERVICE_NAME)
        service_spec = client.V1ServiceSpec(type="ExternalName", external_name=redis_master_name)
        service_body = client.V1Service(
            metadata=service_metadata,
            spec=service_spec,
            kind='Service',
            api_version='v1'
            )

        if not service_exist:
            logging.info(f'Service not exist. Create service: {SERVICE_NAME}. Master is {redis_master_name}')
            try:
                service = v1.create_namespaced_service(namespace=NAMESPACE, body=service_body)
            except Exception as e:
                logging.exception(e)
            continue

        if redis_master_name != external_name:
            logging.info(f'Detected new master - {redis_master_name}. Update service {SERVICE_NAME}')
            try:
                service = v1.patch_namespaced_service(name=SERVICE_NAME,namespace=NAMESPACE, body=service_body)
            except Exception as e:
                logging.exception(e)

        sleep (SLEEP_TIME)

if __name__ == "__main__":
  main()