Node.js中Redis的并发问题

问题

我在Redis中有一个名为stocks的键，它的值是stocks0.假设300个客户同时请求购买(每个客户购买stocks只股票).最后，只有10个客户可以购买.

解决方案

我知道它不会起作用，但假设我的buy函数是这样的:

/**
 * @param {import("redis").RedisClientType} instance
 * @param {string} clientId
 * @param {number} n
 */
async function buy(instance, clientId, n) {
  // --- (1) ----
  // Get current number of stocks
  let stocks = await instance.GET("stocks");
  stocks = parseInt(stocks);

  // --- (2) ----
  // Validate if the stocks remaining are enough to be bought
  if (stocks < n) {
    console.log("error: company does not have enough stocks");
    return new Error("error: company does not have enough stocks");
  }

  // --- (3) ----
  // Update the current stocks of the company and log who has bought stocks
  await instance.INCRBY("stocks", -n);
  console.log("client @%s has bought %s stocks successfully!", clientId, n);
}

为了测试它，我编写了一个调用buy函数300次的函数:

const redis = require("redis");
const crypto = require("crypto");
const { buy } = require("./buy");

async function main(customers = 300) {
  const instance = await redis
    .createClient({ url: "redis://localhost:6379" })
    .connect();

  // --- (1) ----
  // set stocks
  await instance.SET("stocks", 1000);

  // --- (2) ----
  // buy 100 stocks concurrentlly for each customer
  let pool = [];
  for (let i = 0; i < customers; i++) {
    let userId = crypto.randomBytes(4).toString("hex");
    pool.push(buy_v3(instance, userId, 100));
  }
  await Promise.all(pool);

  // --- (3) ----
  // Get the remaining stocks
  let shares = await instance.GET("stocks");
  console.log("the number of free shares the company has is: %s", shares);

  await instance.disconnect();
}
main();

输出:

...
error: company does not have enough stocks
error: company does not have enough stocks
error: company does not have enough stocks
error: company does not have enough stocks
the number of free stocks the company has is: -29000

正如我所说的，它不起作用，但为了解决这个问题，我使用了以下方法:

/**
 * @param {import("redis").RedisClientType} instance
 * @param {string} clientId
 * @param {number} n
 */
async function buy(instance, clientId, n) {
  try {
    await instance.executeIsolated(async (client) => {
      // --- (1) ----
      // Get current number of stocks
      let stocks = await client.GET("stocks");
      stocks = parseInt(stocks);

      // --- (2) ----
      // Validate if the stocks remaining are enough to be bought
      if (stocks < n) {
        throw new Error("error: company does not have enough stocks");
      }

      // --- (3) ----
      // Update the current stocks of the company
      await client.INCRBY("stocks", -n);
    });

    console.log("client @%s has bought %s stocks successfully!", clientId, n);
  } catch (err) {
    console.log(err.message);
  }
}

如果你再次测试它，你会看到类似这样的东西:

...
error: company does not have enough stocks
error: company does not have enough stocks
error: company does not have enough stocks
error: company does not have enough stocks
the number of free stocks the company has is: 0

这意味着它工作起来没有任何问题.

问题

上面的解决方案运行得很好，但我对executeIsolated函数有点困惑.据我所知，它只是创建一个新的连接(您可以看到here)，当您想要在独占连接(如watch命令)上运行命令时，它很有用.

谁能解释一下，在我的 case 中，executeIsolated的确切作用是什么？