bind-sidecar/bind-sidecar.py

#!/usr/bin/env python3
import argparse
import asyncio
import ecs_logging
import logging
import os
import signal
import socket
from kubernetes_asyncio.client.api_client import ApiClient
from kubernetes_asyncio import client, config, watch
from time import time

parser = argparse.ArgumentParser()
parser.add_argument("--replica", action="store_true")
args = parser.parse_args()

# Get the Logger
logger = logging.getLogger()
logger.setLevel(logging.INFO)

# Add an ECS formatter to the Handler
handler = logging.StreamHandler()
handler.setFormatter(ecs_logging.StdlibFormatter())
logger.addHandler(handler)

PATH_CONFIG = "/var/bind/bind.conf"
PATH_ZONEFILE = "/var/bind/db.%s"

active_zones = set()


def update_config():
    master = socket.gethostbyname("bind-primary")
    with open(PATH_CONFIG + ".part", "w") as fh:
        for zone in active_zones:
            path = PATH_ZONEFILE % zone
            if args.replica:
                fh.write("zone \"%s\" { type slave; masters { %s key zone-transfer; }; };\n" % (zone, master))
            else:
                fh.write("zone \"%s\" { type master; file \"%s\"; };\n" % (zone, path))
    os.rename(PATH_CONFIG + ".part", PATH_CONFIG)
    logger.debug("File %s updated", PATH_CONFIG)
    try:
        with open("/var/bind/named.pid") as fh:
            os.kill(int(fh.read()), signal.SIGHUP)
    except FileNotFoundError:
        logger.warn("File /var/bind/named.pid not found, assuming Bind not running yet")


async def update_loop(v1, apps_api, api_instance, revision):
    flt = "codemowers.io", "v1alpha1", "bindzones"
    method = api_instance.list_cluster_custom_object
    w = watch.Watch()
    latest_version = None
    logger.info("Subscribing to updates")
    async for event in w.stream(method, *flt, resource_version=latest_version):
        latest_version = event["object"]["metadata"]["resourceVersion"]
        if event["type"] == "ADDED":
            zone = event["object"]["metadata"]["name"]
            active_zones.add(zone)
            if not args.replica:
                path = PATH_ZONEFILE % zone
                logger.info("Adding zone: %s", zone)
                if not os.path.exists(path):
                    with open(path + ".part", "w") as fh:
                        fh.write("@ IN SOA ns1.%(zone)s. hostmaster.%(zone)s. (1 300 300 300 300)\n" % locals())
                        fh.write("     NS  ns1.%(zone)s.\n" % locals())
                        fh.write("ns1  A   127.0.0.1\n")
                    os.rename(path + ".part", path)
            update_config()
        elif event["type"] == "DELETED":
            logger.info("Removing zone: %s", zone)
            active_zones.remove(zone)
            os.unlink(PATH_ZONEFILE % event["object"]["metadata"]["name"])


async def main():
    if os.getenv("KUBECONFIG"):
        await config.load_kube_config()
    else:
        config.load_incluster_config()
    async with ApiClient() as api:
        v1 = client.CoreV1Api(api)
        apps_api = client.AppsV1Api()
        api_instance = client.CustomObjectsApi(api)
        revision = str(time())
        while True:
            try:
                await update_loop(v1, apps_api, api_instance, revision)
            except asyncio.exceptions.TimeoutError:
                pass


if __name__ == "__main__":
    loop = asyncio.new_event_loop()
    loop.run_until_complete(main())
    loop.close()