nodejs cache app (#301)

nodejs/nodecache-app/README.md

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+# Optimizing Node.js Application Performance with Caching
+
+This README provides a quick guide to start a simple Node.js server project.
+
+Install Dependencies
+
+```bash
+npm install
+```
+
+Start your Node.js server:
+
+```bash
+node index.js
+```
+
+To check Node Server is Working RUN `http://localhost:7000/api/v1/products`

nodejs/nodecache-app/controllers/product.js

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+const productController = {
+  getproducts: async (req, res) => {
+    // emulating data store delay time to retrieve product data
+    await new Promise(resolve => setTimeout(resolve, 750));
+
+    const products = [
+      { id: 1, name: "Desk Bed", price: 854.44 },
+      { id: 2, name: "Shelf Table", price: 357.08 },
+      { id: 3, name: "Couch Lamp", price: 594.53 },
+      { id: 4, name: "Bed Couch", price: 309.62 },
+      { id: 5, name: "Desk Shelf", price: 116.39 },
+      { id: 6, name: "Couch Lamp", price: 405.03 },
+      { id: 7, name: "Rug Chair", price: 47.77 },
+      { id: 8, name: "Sofa Shelf", price: 359.85 },
+      { id: 9, name: "Desk Table", price: 823.21 },
+      { id: 10, name: "Table Shelf", price: 758.91 },
+    ];
+
+    res.json({ products });
+  },
+};
+
+module.exports = { productController };

nodejs/nodecache-app/index.js

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+const express = require("express");
+const {
+  initializeRedisClient,
+  cacheMiddleware,
+  invalidateCacheMiddleware,
+} = require("./middlewares/redis");
+const { productController } = require("./controllers/product");
+
+const app = express();
+app.use(express.json());
+
+// connect to Redis
+initializeRedisClient();
+
+// register an endpoint
+app.get(
+  "/api/v1/products",
+  cacheMiddleware({
+    EX: 3600, // 1h
+  }),
+  productController.getproducts
+);
+
+app.post("/api/v1/product", invalidateCacheMiddleware, (req, res) => {
+  // Implement your logic to update data in Application data store
+  res.json({ message: "Product data updated successfully" });
+});
+
+// start the server
+const port = 7000;
+app.listen(port, () => {
+  console.log(`Server is running on port: http://localhost:${port}`);
+});

nodejs/nodecache-app/middlewares/redis.js

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+const { createClient } = require("redis");
+const hash = require("object-hash");
+let redisClient;
+
+async function initializeRedisClient() {
+  try {
+    redisClient = createClient();
+    await redisClient.connect();
+    console.log("Redis Connected Successfully");
+  } catch (e) {
+    console.error(`Redis connection failed with error:`);
+    console.error(e);
+  }
+}
+
+function generateCacheKey(req, method = "GET") {
+  let type = method.toUpperCase();
+  // build a custom object to use as a part of our Redis key
+  const reqDataToHash = {
+    query: req.query,
+  };
+  return `${type}-${req.path}/${hash.sha1(reqDataToHash)}`;
+}
+
+function cacheMiddleware(
+  options = {
+    EX: 10800, // 3h
+  }
+) {
+  return async (req, res, next) => {
+    if (redisClient?.isOpen) {
+      const key = generateCacheKey(req, req.method);
+
+      //if cached data is found retrieve it
+      const cachedValue = await redisClient.get(key);
+
+      if (cachedValue) {
+        return res.json(JSON.parse(cachedValue));
+      } else {
+        const oldSend = res.send;
+
+        // When the middleware function redisCachingMiddleware is executed, it replaces the res.send function with a custom function.
+        res.send = async function saveCache(data) {
+          res.send = oldSend;
+
+          // cache the response only if it is successful
+          if (res.statusCode >= 200 && res.statusCode < 300) {
+            await redisClient.set(key, data, options);
+          }
+
+          return res.send(data);
+        };
+
+        // continue to the controller function
+        next();
+      }
+    } else {
+      next();
+    }
+  };
+}
+
+function invalidateCacheMiddleware(req, res, next) {
+  // Invalidate the cache for the cache key
+  const key = generateCacheKey(req);
+  redisClient.del(key);
+  next();
+}
+
+module.exports = {
+  initializeRedisClient,
+  cacheMiddleware,
+  invalidateCacheMiddleware,
+};