redis-learnings

Learning Redis in-memory cache from different resources. Comes lets all learn together 💃

“I have not failed. I’ve just found 10,000 ways that won’t work.” – Thomas Edison

What is Redis

• Redis is an in-memory database
• Redis stands for Remote Dictionary Server
• It uses key-value pair storage (JSON)
• It can be used as primary database and also cache
• It runs on RAM so the speed of fetching and reading data is very fast (50X faster than other DB that runs in hard disk)

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Features

Faster Response:

1. As Redis is stores data in RAM, it delivers sub-millisecond response times enabling millions of requests per second
2. That is why many real-time applications are implemented on top of the Redis.

Scalability:

1. It offers single node and multi cluster topology
2. Redis is single-threaded, so uses one thread uses I/O ops
3. It uses master slave architecture
4. It can be scaled horizontally and also vertically

Source: https://www.slideshare.net/RedHatDevelopers/redis-vs-infinispan-devnation-tech-talk

Source https://www.slideshare.net/RedHatDevelopers/redis-vs-infinispan-devnation-tech-talk

Persistence/ Durability:

1. As Redis is in-memory storage, it uses backup technique to store the data in hard-disk to use it in future if node is failed
2. It use RDB & AOF backup mechanism

RDB (Redis Backup):
    - Performs point-in-time snapshots of data at specified interval
    - This is not recommended as we dont have some part of persisted data when node failed as we store till last snapshots
AOF (Append Only File):
    - This will append all the write operations of the redis server
    - This is recommended as we store all the operations and no data is lost

Rich Data-structure:

- Redis is helpful as we can store different type of data in key-value pairs
- Its not associated with the technology limitations

Data structures:
    1. String
    2. Hash
    3. List
    4. Set
    5. Sorted Set
    6. Bitmaps
    7. Streams
    8. Documents

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Use Case

1. Caching:

   • Caching is storing data for temporary period (non-volatile). As Redis is in-memory storage, data persist till RAM is in use
   • It faster to fetch and write data in RAM
   • Web browser engine uses cache to load website faster by fetching domain from cache rather than fetching details from central server

2. Messaging:

   • It can be used in messaging/ chat application
   • It can be used to store last 10 messages using Redis LIST
   • Some of the user details be hashed and can be used in in-memory till chat longs in system

Application Usage

• Redis can be used in Mac and linux by downloading redis from cmd prompt
• In Windows, we need to install redis from WSL
• Alternatively we can use cloud Redis using RedisLabs or Upstash

1. Nodejs (ioredis/ redis)
2. Python (redis)
3. Java (jedis)

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Codings

Nodejs steps

1. Packages used:
   • express
   • ioredis
   • redis
2. Clone this package.json and run cmd "npm install" to install above packages
3. For cloud Redis use below links Upstash, RedisLabs
4. For localhost Redis download and install Redis and Redis cli
5. In server.js use below code to connect to redis (localhost/ cloud)

import express from "express";
import redis from "redis";
import redis from "redis";
const client = redis.createClient({
   host: <HOSTNAME>,
   port: <PORT>,
   password: <PWD>,
 });
await client.connect();
client.on("connect", () => {
   console.log("connected");
});
client.set("foo", "bar");
const value = client.get("foo);

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Reference

1. Fireship 3 mins YT ⭐
2. Redis Free Cloud solution
3. Implementing Redis with Nodejs WDS YT ⭐
4. Hussein Nasser 50 mins YT
5. Techworld with Nana 24 mins YT
6. Redis tech Docs