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Need to store/access your data as fast as possible? Try Redis!

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Why?

"40% of people will leave your site if it takes longer than 3 seconds to load..."
https://econsultancy.com/blog/10936-site-speed-case-studies-tips-and-tools-for-improving-your-conversion-rate
Never make people wait; Learn how to cache your content/app with Redis.

Storing data is a necessity for all (but the simplest) web applications.
Often accessing that data can be the biggest bottleneck in an app causing it to be slow and painful experience.
Redis is designed to be the fastest way to store and retrieve data.
Which means less waiting for the people using your app!

What?

Redis is the closest you can get to direct access (to your computer's) memory.
Written in C the entire server is less than a Megabyte (smaller is better when it comes to executable size), Redis is built for speed.

### Use Case

How?

First Learn the Fundamentals

First thing you need to do - if you haven't already - is go through the online tutorial: http://try.redis.io/ (30mins to learn and take notes)

#### Make Sure you Understand

You can learn/practice all these commands online before installing Redis:

redis> SET count 10
redis> GET count
"10"
redis> INCR count
(integer) 11
redis> DECR count
(integer) 10

Easy, Right? lets keep moving.

Installation

If you don't already have Redis installed on your machine - why would you if you're reading an introductory tutorial, right? - there are two ways to install Redis:

The guys who make Redis suggest compiling it from source (this requires a working GCC compiler and libc) see: Quick Start: http://redis.io/topics/quickstart
If you are running Linux/Mac or prefer not to use Vagrant, try the download & compile described in the quickstart.
For people stuck on Windows (if you don't already have a C Compiler) and people who prefer to "contain" their , we recommend using Vagrant to run Redis (and your app) in a (Linux) Virtual Machine (VM). We have included a Vagrantfile in this repo which you can use to get Redis & Node.js working on any machine. simply:

git clone https://github.com/nelsonic/learn-redis.git && cd learn-redis
vagrant up
vagrant ssh

These three commands will

  1. Clone the repo and move into the new directory
  2. Download and install the Ubuntu VM and latest Redis and Node.js (and start Redis server on TCP Port 6379)
  3. SSH into the Vagrant (Ubuntu) VM so you can use the vagrant CLI

To boot the VM with Redis open a new terminal window/tab (in the learn-redis directory) and issue the command: vagrant up
learn-redis-vagrant-up

After a few minutes of downloading & installing you will see that Redis is running:
learn-vagrant-redis-running

on Port 6379 and PID (process ID) 5786
learn-redis-vagrant-ssh-redis-running

To use Redis from the command line (open a new terminal window/tab and) log into the VM using vagrant ssh:
learn-redis-vagrant-ssh

Then confirm that the CLI is working by issuing the command redis-cli ping: http://stackoverflow.com/questions/10137857/is-redis-just-a-cache learn-redis-vagrant-ssh-redis-ping

To exit the VM you just logged into, simply type exit in the terminal and hit the [return] key.
learn-redis-exit-vagrant-vm

To close the Redis server runing on the VM, press the [ctrl] + [C] keys on your keyboard (twice).
learn-redis-exit-redis

And to shut down the Vagrant VM (to free up the memory on your computer),
issue the vagrant halt command in your terminal:
learn-redis-vagrant-halt

Note: your VM is preserved (still saved on your hard drive) so you can use it again for further redis-development simply by issuing the vagrant up command (from within a working directory that has the Vagrantfile and .vagrant) If you are short on disk space, you can always delete the VM completely by issuing the vagrant destroy command. Note: If you are running Linux on your laptop/dev machine and prefer not to have the overhead of running Vagrant you can simply copy the installation commands from the Vagrantfile and paste them into your terminal.

Which Node.js Module?

A search for "redis" on NPM: https://www.npmjs.com/search?q=redis returns many results!

npm-search-redis

Don't be overwhelmed by the quantity of modules, focus on quality.

The 2 Modules we Use and Recommend

If you (or anyone on your team) using Microsoft Windows (stop hitting yourself!) will need to install a compiler
to get Redis working and that can sometimes take hours!

Our recommendation is to use the redis module because the documentation is better, but install hiredis so that it uses the C binding.

npm install redis hiredis --save

Basic Example

See: examples/basic.js

Paste hand-type (or copy-paste) this code into a file called basic.js

var redis  = require("redis");
var client = redis.createClient();

client.set("Hello", "World", redis.print);

client.get("Hello", function(err, reply) {
   // reply is null when the key is missing
   console.log('Hello ' + reply);
});

Run the script in your terminal by issuing the command: node basic.js You should expect to see:

$ node basic.js
Reply: OK
Hello World

Also Good To Know but Not Essential for this Introductory Tutorial

Redis has many fantastic features not limited to just SET/GET/DELETE key:value pairs. You can also atomically

redis> EXISTS mykey
(integer) 0
redis> APPEND mykey "Hello"
(integer) 5
redis> APPEND mykey " World"
(integer) 11
redis> GET mykey
"Hello World"

redis> SET mykey "10"
OK
redis> INCR mykey
(integer) 11
redis> GET mykey
"11"

If you don't get overwhelmed by lots of new words and want a sneak peek
at the all the cool commands you can use in Redis check: http://redis.io/commands But we're getting ahead of ourselves, lets focus on the basics first.

redis> SET mykey "Hello"
OK
redis> EXPIRE mykey 10
(integer) 1
redis> TTL mykey
(integer) 10
# wait for 10 seconds then
redis> TTL mykey
(integer) -2

RPUSH fruits "Apple"
RPUSH fruits "Banana"
LPUSH fruits "Mango"
LRANGE fruits 0 -1 => 1) "Mango", 2) "Apple", 3) "Banana"
LRANGE fruits 0 1 => 1) "Mango", 2) "Apple"
LRANGE fruits 1 2 => 1) "Apple", 2) "Banana"
LLEN fruits => 3
  1. All the commands in a transaction are serialized and executed sequentially. It can never happen that a request issued by another client is served in the middle of the execution of a Redis transaction. This guarantees that the commands are executed as a single isolated operation.
  2. Either all of the commands or none are processed, so a Redis transaction is also atomic.

Background Reading

General

Which Redis-as-a-Service (Heroku Addon)?

There are a few options for hosted Redis on Heroku: https://addons.heroku.com/?q=redis

Conclusion: rediscloud!

Tips and Tricks

Performance & Benchmarks

Persistence

Because Redis is an in-memory datastore, persistence is not immediate. if you want to be sure that your data is saved, (incase your server/instance is re-booted) read about using the SAVE command.

Graphical User Interface (GUI) for Viewing/Setting Data

Alternative GUIs

Key-Value (KV) Store

There are many KV Stores to chose from: http://en.wikipedia.org/wiki/NoSQL#Key-value_stores our favourites are:

We're here to focus on Redis because it has the right balance of simplicity (great for beginners and pros alike) and speed.

Frequently Asked Questions (FAQ)

### Q: What does Redis mean/stand for?

The name Redis is an acronym for: REmote DIctionary Server

A Dictionary (see: http://xlinux.nist.gov/dads/HTML/dictionary.html) is another way of saying "Key-Value Store";
In other programming languages a dictionary is known as a "map" or "associative array" and would look like this:

{
  "firstName": "John",
  "lastName": "Smith",
  "isAlive": true,
  "age": 25,
  "address": {
    "streetAddress": "21 2nd Street",
    "city": "New York",
    "state": "NY",
    "postalCode": "10021-3100"
  },
  "children": [],
  "spouse": null
}

The observant reader will notice that this looks exactly like a JSON Object; that's because it is! This is how we represent a set of key:value pairs in JS.

It can be easy to think of the real-world dictionary, words are the keys and their definitions are the values.
Imagine you are the person writing the definitions in a dictionary,
you would specify the key (e.g: 'everything') for your item in the dictionary and "SET" the value (e.g: 'awesome').
Then, when you read (or "GET") record for the 'everything' key the value would be 'awesome'.

// basic key:value lookup in JavaScript. Try it: http://repl.it/jYk
var dictionary = {
  'everything':'awesome'
}
for (var k in dictionary) {
  console.log(k + ' is ' + dictionary[k]); // everything is awesome
} // whaaaat? >> https://youtu.be/StTqXEQ2l-Y

Or, sticking with the dictionary metaphor, here's a better example:

// basic key:value dictionary lookup in JavaScript. Try it: http://repl.it/jYk/4
var dictionary = {
  'bycycle':'A bicycle, often called a bike or cycle, is a human-powered, \
pedal-driven, single-track vehicle, having two wheels attached to a frame, \
one behind the other.'
}
for (var k in dictionary) {
  console.log(k +': ' +dictionary[k] );
}

output:

bicycle-definition

Q: Can't I Just Use MongoDB for Everything?

"We are already using MongoDB to store our records, can't we just put everything in one place?"

which-tool-job-hammer-mongodb-fry-futurama-millionaire

MongoDB is a good tool. We like to think of it as the Hammer of Databases
... a general purpose Datastore that works well for most NoSQL situations.
But if you need to save/access Millions of Records Per Second (yes, you read that right!)
then there's only one place to store your data; Redis.

there can be only one

Q: Can we use Redis as Primary Datastore?

Yes! Do it! Discover the power of data structures and the speed of an in-memory datastore!