How to build a Shortened URL By Ruby On Rails like Bitly or Twitter

Give a website shortenedUrl to convert longURL to short URL with alpha lexigraphy encoded/decoded response to User.

• Give two endpoint
  • encoded
  • decoded
• Extra default enpoint is index, and retore lasted encoded url
• About algorithm used on website. I use Bijective algorithm to make a alpha lexigraphy short url.
• Give rate limit process to request IP and prevent attack vector. I was use gem rack-attack for this case to handle limit request per IP is 5 request to 2 second. other wise, better to authentic user before they use api. To do this prevent, can implement a mechanism authentic by a system by api key for user indetify and in session.
• System was give an URL with a unique shortURL to decrease weight in database and open scale up if have mutilple dabase installed.
• To prepare for scale up:
  1. Give a better cache system support Rate limit.
  2. With URL was created before, we change to operation select instead create same URL.
  3. Given a load ballancing to suppot this load is even better than server serve every single request.
  4. Architecture from Monolith or micro service and under control of load balancing give us a good reputation.

Install System

• Ruby version ^2.5~3.0
• Rails
• rack-attack gem
• Rspec
• factory_bot_rails
• faker

To install run command below:

1
bundle

API in use

Three enpoint with two default enpoint(/api/v1/shortner/):

• index /api/v1/shortner: Get method
  json response:

  1
  2
  3
  4
  5
  {
    "message": "Hello shortner",
    "encoded": "q",
    "url": "http://google.com"
  }
  

• encoded /api/v1/shortner/encoded: Post method
  Json request:

  1
  2
  3
  {
    "url": "http://google.com"
  }
  

  Json Response

  1
  2
  3
  4
  {
    "url": "http://google.com",
    "decoded": "b"
  }
  

• decoded request /api/v1/shortner/decoded: Post method
  Json Request

  1
  2
  3
  {
    "encoded": "e"
  }
  

  Json Response

  1
  2
  3
  4
  {
    "url": "http://google.com",
    "status": 200
  }
  

Last URL saved

• Last user saved was restore in Database. I was use default by sqlite3. But for better performance and production case need to setup dabase with MYSQL or PostgresSQL.

encoded

1
2
3
4
  def generate_slug
    last_id = ShortenUrl.last ? ShortenUrl.last.id : 1
    self.slug = Bijective.bijective_encode(last_id)
  end

decoded

1
2
url = ShortenUrl.find_by_slug params[:encoded]
url.url

Algorithm to conver longURL to Short

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
class Bijective
  ALPHABET =
    "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789".split(//)
    # make your own alphabet using:
    # (('a'..'z').to_a + ('A'..'Z').to_a + (0..9).to_a).shuffle.join

  def self.bijective_encode(i)
    # from http://refactormycode.com/codes/125-base-62-encoding
    # with only minor modification
    return ALPHABET[0] if i == 0
    s = ''
    base = ALPHABET.length
    while i > 0
      s << ALPHABET[i.modulo(base)]
      i /= base
    end
    s.reverse
  end

  def self.bijective_decode(s)
    # based on base2dec() in Tcl translation 
    # at http://rosettacode.org/wiki/Non-decimal_radices/Convert#Ruby
    i = 0
    base = ALPHABET.length
    s.each_char { |c| i = i * base + ALPHABET.index(c) }
    i
  end
end

Test application with Spec

Test case was specified with controller and function endoint. To run test from root of project run command:

1
rspec

Sumarize

Give a website for serve enpoint to convert long url to short url, you can find source code at my github repository.