Redis

What is Redis?

Redis is a cache system and in-memory database that stores data in a key-value format. Since in-memory databases store all data in memory, they are much faster than retrieving data from a traditional DBMS. Redis utilizes a data structure called Sorted-Set to sort data more quickly and easily.

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I wanted to use Redis to store refresh tokens. I tried to use the elastic cache provided by AWS, but it charged me. I also tried to download redis-server directly to EC2 and connect it, but it didn't work. Finally, I found a solution in Redislabs, which provides a free Redis DB with a size limit of 30MB.

How to Connect Redis with Node.js Project

1. Click Try Free and sign up in Redislabs

2. Select AWS and Region: US East (N.Virginia) us-east-1

3. You can now see the free DB is created.

4. Under Name, we can see important information we are going to use in the project.

• host, post: we can copy host and port info. For host, we should omit the port number at the end of the endpoint (e.g. :19231)

  

• password: we can copy randomly generated password by scrolling down a bit

1. On Terminal, run the following commands:

• Windows

> npm install -g redis-cli # install redis cli

> rdcli -h <host> -p <port> -a <password> # connect to redis cloud

• Linux

$ apt-get install redis-tools # install redis cli

$ redis-cli -v # check version

$ redis-cli -h <endpoint> -p <port> -a <password> # oonnect to redis cloud

1. Add the environment variables

• npm install dotenv: install the environment variables module

• .env file will be automatically created under the root directory

• Enter the following info:

# .env file
REDIS_HOST=redis-10943.c114.us-east-14.ec2.cloud.redislabs.com
REDIS_PORT=10943
REDIS_USERNAME=default
REDIS_PASSWORD=abcdefghijklmnopqrstuvwsyz

1. Install redis module

• npm install redis

1. Connect redis to the local

• import redis and dotenv modules

const redis = require("redis");
require("dotenv").config();

const redisClient = redis.createClient({ 
  url: `redis://${process.env.REDIS_USERNAME}:${process.env.REDIS_PASSWORD}@${process.env.REDIS_HOST}:${process.env.REDIS_PORT}/0`,
  legacyMode: true
}); // set the legacy mode (v4 updated version is based on the Promise, but if you want to use v3 version based on the callback, you must set legacy mode_
redisClient.on('connect', () => {
   console.info('Redis connected!');
});
redisClient.on('error', (err) => {
   console.error('Redis Client Error', err);
});
redisClient.connect().then(); // connect to redis v4 (async)
const redisCli = redisClient.v4;

1. Use Redis in JavaScript

   1. Save data: let bool = await redisClient.v4.set('key', '123');

   2. Bring data: let data = redisClient.v4.get('key');

      IMPORTANT: TypeError: A key should not be a Number type

   3. Delete data: const n = await redisCli.exists('username'); -> check if exists
      if(n) await redisCli.del('username'); -> delete

   4. Modify data: redisCli.rename('key', 'changed'); -> if key exists, change value to 'changed'

2. Defind Redis Class

class RedisClientRepository {
    constructor() {
        this.redisClient = redis.createClient({
            url: `redis://${process.env.REDIS_USERNAME}:${process.env.REDIS_PASSWORD}@${process.env.REDIS_HOST}:${process.env.REDIS_PORT}/0`,
            legacyMode: true,
        });

        this.redisConnected = false;
    }

    initialize = async () => {
        this.redisClient.on("connect", () => {
            this.redisConnected = true;
            console.info("Redis connected!");
        });
        this.redisClient.on("error", (err) => {
            console.error("Redis Client Error", err);
        });
        if (!this.redisConnected) this.redisClient.connect().then(); // redis v4 connection (async)
    };

    setRefreshToken = async (refreshToken, userId) => {
        await this.initialize();
        await this.redisClient.v4.set(refreshToken, userId);
    };

    getRefreshToken = async (refreshToken) => {
        await this.initialize();
        const token = await this.redisClient.v4.get(refreshToken);
        return token;
    };

    deleteRefreshToken = async (refreshToken) => {
        await this.initialize();
        await this.redisClient.v4.del(refreshToken);
    };
}