Express and node cache tutorial

This is a quick tutorial on how to cache api calls.

What is caching?

Caching is the storing of data temporarily and retrieving data from a high-performance store (usually memory) either explicitly or implicitly.

Advantage: When using external api's, you may have a restricted number of calls or cost per api call. If your api data doesn't constantly update, this not only reduces the number of api calls made but also reduces the loading speed.

Installation

Firstly, navigate to the directory where you would like to store your project from your terminal. Let's start by making our project.

Run the following command in your terminal:

mkdir cache-project
cd cache-project

Now let's initiate our package.json file with the default parameters and install our packages with the following commands:

npm init -y
npm i express node-cache axios cors

These commands should create a package.json which looks like this:

{
  "name": "cache-project",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "axios": "^0.27.2",
    "cors": "^2.8.5",
    "express": "^4.18.1",
    "node-cache": "^5.1.2"
  }
}

Now let's breakdown the packages:

1. axios - We'll use this package to make our api calls
2. cors - This will enable our server to interact with our client.
3. express - Our server of course.
4. node-cache - This is our cache middleware package.

Server and Router

We'll now create our server and router:

touch index.js router.js

Let's paste the following code to our index.js file:

const express = require("express");
const cors = require("cors");
const router = require("./router");
const App = express();
const Port = 8000; // Our server port

App.use(express.json());
App.use(cors());
App.use(router);

App.listen(Port, () => {
  console.log(`Cache app listening at http://localhost:${Port}/`);
});

Now let's quickly breakdown what we've just done:

1. Created our server and declared it on port 8000.
2. Added our parser using express.json, added our cors and router (which we will add shortly).
3. Add a listener to signal our server is running.

Now let's create a quick router with a default home route and export it.

Let's paste the following code to our router.js file:

const { Router } = require("express");
const router = Router();

router.get("/", (req, res) => {
  res.send("Cache Project Home Page");
  res.status(200);
});

module.exports = router;

Middleware

Let's now move onto our middleware. Let's start by creating a middleware folder and a file which we'll call crypto.cache.js.

mkdir middleware
touch middleware/crypto.cache.js

Now let's add the following to our crypto.cache.js:

const Cache = require("node-cache");
const cryptoCache = new Cache({ stdTTL: 60 * 5 });

const cryptoCacheMiddleware = (req, res, next) => {
  try {
    if (cryptoCache.has("crypto-list")) {
      return res.send(cryptoCache.get("crypto-list")).status(200);
    }
    return next();
  } catch (err) {
    console.log(err);
    throw err;
  }
};

module.exports = {
  cryptoCacheMiddleware,
  cryptoCache,
};

Let's breakdown what we've just done.

1. Imported node-cache and set the new Cache to 5 minutes ({ stdTTL: 60 * 5 })
2. We'll make an async middleware function name cryptoCacheMiddleware.
3. Like any controller in express our middleware will take a req and res argument. In addition to this we'll add a next to skip this function if the conditions of our if statement is not met.
4. The cryptoCache checks if something has been stored under the name crypto-list
5. If something is stored under crypto-list then the get will return it rather than skipping to the controller.

Services

Now we'll create a services folder which will store all our api calls.

mkdir services
touch services/fetch.js services/crypto.services.js

First, let's create a async fetch function using axios. Paste the following code into our fetch.js file.

const axios = require("axios");

const FetchApi = async (url) => {
  try {
    const res = await axios.get(url);
    return res.data;
  } catch (err) {
    console.log(err);
    throw err;
  }
};

module.exports = FetchApi;

Now let's import that FetchApi function into our crypto.services.js file and create our api call.

const FetchApi = require("./fetch");

const cryptoApi = async (amount) => {
  try {
    const result = await FetchApi(
      "https://api2.binance.com/api/v3/ticker/24hr"
    );
    return result.slice(0, amount);
  } catch (err) {
    console.log(err);
    throw err;
  }
};

module.exports = {
  cryptoApi,
};

Let's quickly breakdown the code:

1. We've made an async function which takes the argument name amount.
2. Then we'll use FetchApi to make an api call from: https://api2.binance.com/api/v3/ticker/24hr
3. Finally we'll return the results and the number of results is determined by our amount argument.

Controllers

Finally we'll create our controllers so let's run the following command in our terminal:

mkdir controllers
touch controllers/crypto.controllers.js

This should return a directory named controllers contianing a file named crypto.controllers.js.

const { cryptoCache } = require("../middleware/crypto.cache");
const { cryptoApi } = require("../services/crypto.services");

const cryptoController = async (req, res) => {
  try {
    const data = await cryptoApi(25);
    cryptoCache.set("crypto-list", data);
    res.send(data);
    res.status(200);
  } catch (err) {
    res.status(500);
    console.log(err);
    throw err;
  }
};

module.exports = {
  cryptoController,
};

Updating our router

Finally let's update router.js file but adding our middleware and controller.

const { Router } = require("express");
const router = Router();
const { cryptoController } = require("./controllers/crypto.controllers");
const { cryptoCacheMiddleware } = require("./middleware/crypto.cache");

router.get("/", (req, res) => {
  res.send("Cache Project Home Page");
  res.status(200);
});
router.get("/crypto", cryptoCacheMiddleware, cryptoController);

module.exports = router;

Run the server:

node index.js

Running our server

Make the a GET request using the following link: http://localhost:8000/crypto.

You'll notice that the first call will take a couple seconds, but then if you re-run the call, for the next 5 minutes, it will return the same result from your first call instantly.

And that's all she wrote! Thanks for reading!