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#!/usr/bin/env python3

"""

main.py

Run a single cache shard *or* spin-up a 3-node demo cluster.

• one shard: python main.py --port 5001

• demo: python main.py --demo

Extra flags

-----------

--threads N worker threads per shard (Waitress only, default 8)

--capacity N max cache items (default from config)

--default-ttl N seconds default TTL (default from config)

--no-quiet show Flask/Waitress access log

"""

from __future__ import annotations

import argparse

import logging

import multiprocessing as mp

import time

from typing import List

from flask import Flask, jsonify, request

import config

from lru_cache import LRUCache

from replication import Replicator

from shard_manager import ShardManager

# ─────────────────────────────────────────────────────────────────────────────

# Flask factory – each shard gets its *own* cache instance

# ─────────────────────────────────────────────────────────────────────────────

def create_app(capacity: int, default_ttl: int) -> Flask:

app = Flask(__name__)

cache = LRUCache(capacity=capacity, default_ttl=default_ttl)

@app.route("/cache/<key>", methods=["GET"])

def http_get(key: str):

val = cache.get(key)

return jsonify({"value": val}), (200 if val is not None else 404)

@app.route("/cache/<key>", methods=["POST"])

def http_put(key: str):

data = request.get_json(force=True)

cache.put(key, data["value"], ttl=data.get("ttl"))

return jsonify(ok=True), 200

@app.route("/health", methods=["GET"])

def health():

return jsonify(status="up"), 200

return app

# ─────────────────────────────────────────────────────────────────────────────

# Shard launcher – Waitress w/ keep-alive, falls back to Flask dev server

# ─────────────────────────────────────────────────────────────────────────────

def run_shard(

port: int,

capacity: int,

default_ttl: int,

threads: int,

quiet: bool,

) -> None:

if quiet:

logging.getLogger("werkzeug").setLevel(logging.WARNING)

logging.getLogger("waitress").setLevel(logging.WARNING)

app = create_app(capacity, default_ttl)

try:

from waitress import serve

serve(

app,

host="127.0.0.1",

port=port,

threads=threads,

connection_limit=10_000, # plenty for local benchmarks

)

except ImportError:

# ── fallback: Flask dev server (good for quick tests, not for load) ──

app.run(

host="127.0.0.1",

port=port,

threaded=True,

use_reloader=False, # no double-fork on Windows

)

# ─────────────────────────────────────────────────────────────────────────────

# Demo helper – launches three shard processes, runs the original test

# ─────────────────────────────────────────────────────────────────────────────

def run_demo(

ports: List[int],

capacity: int,

default_ttl: int,

threads: int,

quiet: bool,

) -> None:

procs: List[mp.Process] = [

mp.Process(

target=run_shard,

args=(p, capacity, default_ttl, threads, quiet),

daemon=True,

)

for p in ports

]

for p in procs:

p.start()

time.sleep(2) # give the servers time to bind

shard_mgr = ShardManager(config.SHARD_ENDPOINTS)

replicator = Replicator(

list(config.SHARD_ENDPOINTS.items()), config.REPLICATION_FACTOR

)

replicator.put("foo", "bar", ttl=60)

time.sleep(0.5)

print("GET foo:", shard_mgr.get("foo"))

# LRU eviction

for i in range(capacity + 5):

shard_mgr.put(f"key{i}", f"val{i}")

print("GET key0 (evicted):", shard_mgr.get("key0"))

# TTL expiry

shard_mgr.put("temp", "123", ttl=1)

time.sleep(2)

print("GET temp (expired):", shard_mgr.get("temp"))

# shutdown

for p in procs:

p.terminate()

p.join()

# ─────────────────────────────────────────────────────────────────────────────

# CLI

# ─────────────────────────────────────────────────────────────────────────────

def parse_args() -> argparse.Namespace:

p = argparse.ArgumentParser(description="Distributed-LRU cache shard / demo")

g = p.add_mutually_exclusive_group(required=True)

g.add_argument("--port", type=int, help="Run a single shard on this port")

g.add_argument("--demo", action="store_true", help="Run the 3-node demo")

p.add_argument("--threads", type=int, default=8, help="Worker threads per shard")

p.add_argument("--capacity", type=int, default=config.CAPACITY)

p.add_argument("--default-ttl", type=int, default=config.DEFAULT_TTL)

p.add_argument(

"--no-quiet", action="store_true", help="Show access log (very noisy)"

)

return p.parse_args()

def main() -> None:

args = parse_args()

quiet = not args.no_quiet

if args.demo:

run_demo([5001, 5002, 5003], args.capacity, args.default_ttl, args.threads, quiet)

else:

run_shard(args.port, args.capacity, args.default_ttl, args.threads, quiet)

if __name__ == "__main__":

main()