index.js

/**
 *      Title: NODE EXPRESS CACHING FETCHED DATA with REDIS
 *      Description: This code is a demo on caching data with Redis to lower latency and speed up load time
 *      Credits: API credits to www.messari.io
 */

const express = require("express");
const redis = require("redis");
const fetch = require("node-fetch");

let PORT = process.env.PORT || 4000;
let REDIS_PORT = process.env.PORT || 6379;

const client = redis.createClient(REDIS_PORT);
const app = express();

// FETCH DATA FROM API
// credits to www.messari.io
async function coin(request, response) {
  try {
    console.log("fetching data...");
    const { coin } = request.params;
    const respond = await fetch(
      `https://data.messari.io/api/v1/assets/${coin}/profile`
    );
    const data = await respond.json();

    // current variable convert json to string format
    const current = JSON.stringify(data);

    // set cache with expiration
    client.setex("coin", 3600, current);

    return response.send({ Coin: coin, 'Fresh Data': data });
  } catch (error) {
    response.send({ 'Something went wrong on "GET_COIN" function': error });
  }
}

//CACHE MIDDLEWARE
function cache(request, response, next) {
  const { coin } = request.params;

  // retreive data from the cache
  client.get("coin", (error, data) => {

    //parsed data to convert string to json format
    const parsed = JSON.parse(data);
    if (error)
      response.send({
        "Something went wrong on getting data from the cache": error,
      });

    if (data !== null && parsed.data.slug === coin) {
        return response.send({ Coin: coin, 'Cached Data': parsed });
    }
    else {
      next();
    }
  });
}

//ROUTER
app.get("/crypto/:coin", cache, coin);

//PORT LISTENER
app.listen(PORT, () => {
  console.log("listening to port", PORT);
});