# Background
**Caching** is a process of storing data generated by new requests in order to serve similar requests in the future more swiftly. 
When developing a web-application, caching serves as an essential tool to manage requests and speed-up the response time. Through caching, web sites running on a single server with a single database can sustain a load of thousands of concurrent users.

Memcache is one of the different *caching* systems. **Memcache** caches objects in **RAM** to speed up access to the content. Content is directly fetched from memory instead of from an external data source. One of the most popular *memcache* servers is provided by **Danga**, an open-source software. 

# Memcache in Ruby on Rails

**Ruby on Rails** uses the Danga server coupled with  #key# **Dalli**: a high-performance **Ruby** client to serve *memcache* #key# to provide centralized caching for the application. This memcache cache store can offer a single, shared server to provide high performance, high availability, and fast access to content. To initialize, the developer needs to input all the addresses of memcache servers; otherwise, it will be initialized on the localhost using the default port, which is not ideal for sites that generate a massive amount of requests.



# Installing memcache on Ruby on Rails

> This installation setup is for Ubuntu.


## Step 1
Use the following command to install memcache:
```terminal
sudo apt install memcached
```

## Step 2 (optional)

If you already have rubygems installed on your system, skip this step. Otherwise, install rubygems using the follwing command: 
```terminal
sudo apt-get install rubygems
```

## Step 3
Install Dalli using the following command:
```terminal
sudo gem install dalli
```

After that, add the following: line in your gemfile:
```terminal
gem 'dalli'
```
Finally, execute this command:
```terminal
bundle install
```


# Working with memcache

In order to open up a connection to memcache using Dalli, use the following dummy code:
```ruby
require 'dalli'

options = { :username => 'username', :password => 'password' }
mc = Dalli::Client.new('hostname:port', options)
```
To make this snippet of code compatible with your code, change `:username`, `:password`, and `hostname:port` according to the variables in your bucket.

Reading and writing data on memcache is straight forward. Observe the following code snippet:
```ruby
mc.set('drink', 'tea')
value = mc.get('drink')
puts value
```
The above code will store key-value pairs in memcache. The key is **drink** and it has a value of **tea**. Use the `.set()` method to place a key-value pair on memcache and use the `.get()` method to retrieve a value using a key from the memcache.

What is Memcache in Ruby on Rails?

Caching stores generated data to serve similar future requests quickly. Memcache in Ruby on Rails uses Dalli for centralized, high-performance caching.