Lua والـ Atomicity في Redis: كام أمر كأنهم أمر واحد

import Redis from "ioredis";

const redis = new Redis(process.env.REDIS_URL);
await redis.flushall();
await redis.set("stock:book", 10);

// ❌ اقرا، وقرّر في Node، واكتب: 3 أوامر منفصلة
async function buy() {
  const stock = Number(await redis.get("stock:book"));
  if (stock <= 0) return false;
  await redis.set("stock:book", stock - 1);
  return true;
}

const results = await Promise.all(Array.from({ length: 30 }, buy));
console.log("اتباع:", results.filter(Boolean).length, "| المخزون:", await redis.get("stock:book"));
redis.disconnect();

$ node main.js
اتباع: 30 | المخزون: 9

import Redis from "ioredis";

const redis = new Redis(process.env.REDIS_URL);
await redis.flushall();
await redis.set("stock:book", 10);

// WATCH + MULTI: optimistic locking. لو حد غيّر الـ key بعد WATCH، الـ EXEC بيفشل (null)
async function buy() {
  const c = redis.duplicate(); // WATCH مربوط بالـ connection
  try {
    for (let attempt = 0; attempt < 50; attempt++) {
      await c.watch("stock:book");
      const stock = Number(await c.get("stock:book"));
      if (stock <= 0) {
        await c.unwatch();
        return false;
      }
      const ok = await c.multi().set("stock:book", stock - 1).exec();
      if (ok) return true; // null = حد سبقنا، جرّب تاني
    }
    return false;
  } finally {
    c.disconnect();
  }
}

const results = await Promise.all(Array.from({ length: 30 }, buy));
console.log("اتباع:", results.filter(Boolean).length, "| المخزون:", await redis.get("stock:book"));
redis.disconnect();

$ node main.js
اتباع: 10 | المخزون: 0

import Redis from "ioredis";

const redis = new Redis(process.env.REDIS_URL);
await redis.flushall();
await redis.set("stock:book", 10);

// Lua: الـ script كله بيتنفذ كأنه أمر واحد، ومحدش يدخل في النص
redis.defineCommand("buy", {
  numberOfKeys: 1,
  lua: `
    local stock = tonumber(redis.call('GET', KEYS[1]) or '0')
    if stock <= 0 then return 0 end
    redis.call('DECR', KEYS[1])
    return 1
  `,
});

const results = await Promise.all(Array.from({ length: 30 }, () => redis.buy("stock:book")));
console.log("اتباع:", results.filter((r) => r === 1).length, "| المخزون:", await redis.get("stock:book"));

// الاستخدام الكلاسيكي: فك lock بس لو أنا صاحبه
redis.defineCommand("unlock", {
  numberOfKeys: 1,
  lua: `
    if redis.call('GET', KEYS[1]) == ARGV[1] then
      return redis.call('DEL', KEYS[1])
    end
    return 0
  `,
});
await redis.set("lock:report", "worker-1", "PX", 30000);
console.log("worker-2 بيفك lock مش بتاعه:", await redis.unlock("lock:report", "worker-2"));
console.log("worker-1 بيفك الـ lock بتاعه:", await redis.unlock("lock:report", "worker-1"));
redis.disconnect();

$ node main.js
اتباع: 10 | المخزون: 0
worker-2 بيفك lock مش بتاعه: 0
worker-1 بيفك الـ lock بتاعه: 1

import Redis from "ioredis";

const redis = new Redis(process.env.REDIS_URL);
await redis.flushall();
await redis.set("seats:node-live", 50);


redis.defineCommand("reserve", {
  numberOfKeys: 2,
  lua: `
    if redis.call('SISMEMBER', KEYS[2], ARGV[1]) == 1 then return -1 end
    local seats = tonumber(redis.call('GET', KEYS[1]) or '0')
    if seats <= 0 then return 0 end
    redis.call('DECR', KEYS[1])
    redis.call('SADD', KEYS[2], ARGV[1])
    return 1
  `,
});

const users = [
  ...Array.from({ length: 120 }, (_, i) => `user-${i + 1}`),
  ...Array.from({ length: 80 }, (_, i) => `user-${i + 1}`),
];
const results = await Promise.all(users.map((u) => redis.reserve("seats:node-live", "booked:node-live", u)));
const count = (x) => results.filter((r) => r === x).length;
console.log("1:", count(1), "| 0:", count(0), "| -1:", count(-1));
console.log("seats:", await redis.get("seats:node-live"), "| booked:", await redis.scard("booked:node-live"));
redis.disconnect();

$ node main.js
1: 50 | 0: 100 | -1: 50
seats: 0 | booked: 50