example.py

import argparse
import logging
import os
import sys
import time

import redis

from redis_hashring import RingNode

N_KEYS = 100

logging.basicConfig(level=logging.DEBUG)


def _parse_arguments():
    parser = argparse.ArgumentParser("Hash ring example.", add_help=False)
    parser.add_argument(
        "--host", "-h", default="localhost", help="Redis hostname."
    )
    parser.add_argument(
        "--port", "-p", type=int, default=6379, help="Redis port."
    )
    parser.add_argument(
        "--print",
        action="store_true",
        dest="print",
        help="Print the hash ring.",
    )
    parser.add_argument(
        "--help",
        action="help",
        default=argparse.SUPPRESS,
        help="Show this help message and exit.",
    )
    return parser.parse_args()


if __name__ == "__main__":
    args = _parse_arguments()

    print(f"Attempting to connect to Redis at {args.host}:{args.port}.")
    r = redis.Redis(args.host, args.port)
    try:
        r.ping()
    except redis.exceptions.ConnectionError:
        print("Failed to connect to Redis.")
        sys.exit(1)

    node = RingNode(r, "ring")

    if args.print:
        node.debug_print()
        sys.exit()

    pid = os.getpid()

    node.start()

    try:
        while True:
            keys = [key for key in range(N_KEYS) if node.contains(str(key))]
            logging.info("PID %d, %d keys (%s)", pid, len(keys), repr(keys))
            time.sleep(2)
    except KeyboardInterrupt:
        pass

    node.stop()