Caching design pattern กับ backend

version: "3.7"

services:
  db:
    image: mysql:latest
    container_name: mysql_db
    command: --default-authentication-plugin=mysql_native_password
    environment:
      MYSQL_ROOT_PASSWORD: root
      MYSQL_DATABASE: tutorial
    ports:
      - "3306:3306"
    volumes:
      - mysql_data:/var/lib/mysql

  phpmyadmin:
    image: phpmyadmin/phpmyadmin:latest
    container_name: phpmyadmin
    environment:
      PMA_HOST: db
      PMA_PORT: 3306
      PMA_USER: root
      PMA_PASSWORD: root
    ports:
      - "8080:80"
    depends_on:
      - db

  redis:
    image: redis:latest
    container_name: redis-container
    ports:
      - "6379:6379"

volumes:
  mysql_data:
    driver: local

const express = require("express");
const bodyparser = require("body-parser");
const mysql = require("mysql2/promise");
const redis = require("redis");
const cron = require("node-cron");

const app = express();

app.use(bodyparser.json());

const port = 8000;

let conn = null;
let redisConn = null;

// function init connection mysql
const initMySQL = async () => {
  conn = await mysql.createConnection({
    host: "localhost",
    user: "root",
    password: "root",
    database: "tutorial",
  });
};

// function init connection redis
const initRedis = async () => {
  redisConn = redis.createClient();
  redisConn.on("error", (err) => console.log("Redis Client Error", err));
  await redisConn.connect();
};

// เคสแบบไม่ใช้ cache สำหรับดึง users ทั้งหมดออกมา
app.get("/users", async (req, res) => {
  const results = await conn.query("SELECT * FROM users");
  res.json(results[0]);
});

/*
เพื่อให้เอกสารอ่านง่ายขึ้น code ด้านล่างต่อจากนี้ เราจะเพิ่ม code เพียงแค่บริเวณนี้เท่านั้น สำหรับการทดลองนี้ เท่านั้น
*/

app.listen(port, async (req, res) => {
  await initMySQL();
  await initRedis();
  console.log("http server run at " + port);
});

app.get("/users/cache-1", async (req, res) => {
  try {
    const cachedData = await redisConn.get("users");

    if (cachedData) {
      // มี cache = ใช้ cache ก่อนไปเลย
      res.json(JSON.parse(cachedData));
      return;
    }

    // User data not found in cache, fetch from MySQL
    const [results] = await conn.query("SELECT * FROM users");
    // Store user data in Redis cache
    await redisConn.set("users", JSON.stringify(results));
    res.json(results);
  } catch (error) {
    console.error("Error:", error);
    res.status(500).json({ error: "An error occurred" });
  }
});

// api สำหรับ get
app.get("/users/cache-2", async (req, res) => {
  try {
    const cachedData = await redisConn.get("users-2");
    if (cachedData) {
      // มี cache = ใช้ cache ก่อนไปเลย
      res.json(JSON.parse(cachedData));
      return;
    }

    // User data not found in cache, fetch from MySQL
    const [results] = await conn.query("SELECT * FROM users");
    res.json(results);
  } catch (error) {
    console.error("Error:", error);
    res.status(500).json({ error: "An error occurred" });
  }
});

// api สำหรับเพิ่ม users + เขียนลง cache เพิ่ม
app.post("/users", async (req, res) => {
  try {
    let user = req.body;
    // insert ข้อมูลใส่ database
    const [results] = await conn.query("INSERT INTO users SET ?", user);
    user.id = results.insertId;

    // เขียน cache ใหม่ด้วย
    let cachedData = await redisConn.get("users-2");
    let newData = [];

    if (cachedData) {
      const loadDataCache = JSON.parse(cachedData);
      newData = loadDataCache.concat(user);
      await redisConn.set("users-2", JSON.stringify(newData));
    } else {
      const [results] = await conn.query("SELECT * FROM users");
      await redisConn.set("users-2", JSON.stringify(results));
    }

    res.json({
      message: "insert ok",
      dataAdded: user,
    });
  } catch (error) {
    console.error("Error:", error);
    res.status(500).json({ error: "An error occurred" });
  }
});

app.get("/users/cache-3", async (req, res) => {
  try {
    const cachedData = await redisConn.get("users-3");
    if (cachedData) {
      // มี cache = ใช้ cache ก่อนไปเลย
      res.json(JSON.parse(cachedData));
      return;
    }

    // User data not found in cache, fetch from MySQL
    const [results] = await conn.query("SELECT * FROM users");
    res.json(results);
  } catch (error) {
    console.error("Error:", error);
    res.status(500).json({ error: "An error occurred" });
  }
});

app.put("/users/:id", async (req, res) => {
  try {
    let user = req.body;
    let id = parseInt(req.params.id);
    user.id = id;

    // เขียน cache ใหม่ด้วย
    let cachedData = await redisConn.get("users-3");
    let updateIndexList = (await redisConn.get("update-users-3")) || [];

    let updateData = "";
    if (cachedData) {
      const loadDataCache = JSON.parse(cachedData);
      let selectedIndex = loadDataCache.findIndex((user) => user.id === id);
      loadDataCache[selectedIndex] = user;
      updateIndexList.push(selectedIndex);
      updateData = loadDataCache;
    } else {
      const [results] = await conn.query("SELECT * FROM users");
      let selectedIndex = results.findIndex((user) => user.id === id);
      results[selectedIndex] = user;
      updateIndexList.push(selectedIndex);
      updateData = results;
    }

    await redisConn.set("users-3", JSON.stringify(updateData));
    await redisConn.set("update-users-3", JSON.stringify(updateIndexList));

    res.json({
      message: "update ok",
      dataAdded: user,
    });
  } catch (error) {
    console.error("Error:", error);
    res.status(500).json({ error: "An error occurred" });
  }
});

let waiting = false;
cron.schedule("*/10 * * * * *", async () => {
  console.log("running every 10 seconds", waiting);
  try {
    if (waiting) {
      return;
    }
    const cachedData = await redisConn.get("users-3");
    const updateIndexListCached = await redisConn.get("update-users-3");

    if (updateIndexListCached) {
      waiting = true;
      const updateIndexList = JSON.parse(updateIndexListCached);
      const userData = JSON.parse(cachedData);

      for (let i = 0; i < updateIndexList.length; i++) {
        const index = updateIndexList[i];
        const selectedUser = userData[index];

        const id = selectedUser.id;
        const updateUser = {
          name: selectedUser.name,
          age: selectedUser.age,
          description: selectedUser.description,
        };

        const [results] = await conn.query("UPDATE users SET ? WHERE id = ?", [updateUser, id]);

        console.log("=== update complete !", results);
      }

      await redisConn.del("update-users-3");
      waiting = false;
    }
  } catch (error) {
    console.error("Error:", error);
    res.status(500).json({ error: "An error occurred" });
  }
});