README.md

url-shortener

About

An simple URL shortener RESTful web service API written in Go, using the net/http package for the server, the HttpRouter for the router and Bolt DB for the database.

Deployed on Heroku, access it on url-shortener-thanoskoutr.herokuapp.com

See below for API Documentation

Usage

Run service

To run the web service:

$ git clone https://github.com/thanoskoutr/url-shortener.git
$ cd url-shortener
$ go run main.go

Starting the server on :8080

Build executable

To build and run the web service as an executable:

$ go build
$ ./url-shortener

Starting the server on :8080

Call the API

Shorten a URL:

$ curl -X POST http://localhost:8080/shorten -d '{"long_url":"https://www.github.com"}'

{"long_url":"https://www.github.com","short_url":"GJWrQa0"}

Access the URL you shortened from the following new URL:

$ curl http://localhost:8080/redirect/GJWrQa0

<a href="https://www.github.com">Moved Permanently</a>.

Testing

To run the tests for all subpackages (recursively):

$ go test -v ./...

Dependencies

To fetch the dependencies from go.mod:

$ go mod download

To create the go.mod from scratch (only for dev purposes), run:

$ go mod init github.com/thanoskoutr/url-shortener
$ go get github.com/boltdb/bolt
$ go get github.com/julienschmidt/httprouter
$ go get github.com/rs/cors
$ go mod tidy

Deployment

For instruction on how to deploy this Go web service (or any other Go app) for free on a Platform as a Service cloud provider like Heroku, see the Heroku Deployment Guide.

Features

• Create Short URL from Long URL (/shorten endpoint)
  • Get a Long URL from user, as a JSON body parameter
  • Use encoding algorithm (MD5 Hash and base64 encoding)
  • Save (Short URL, Long URL) key-value pair in Database
  • Return Short URL as a JSON response to the user
• Redirect server (/redirect/:short_url endpoint)
  • If :short_url parameter is not empty, redirect to saved Long URL on Database
  • If :short_url parameter is empty, redirect to Home page (/)

API Specification

You can find the API Documentation on Spotlight.

Contains:

• API Documentation.
• Ability to make calls to the API Endpoints of the service.

BoltDB Web Interface

We can inspect the BoltDB database in the browser using the boltdbweb tool.

To install it globally (usually in the ~/go/bin folder in your system), run:

go install github.com/evnix/boltdbweb@latest

Usage:

boltdbweb -d urls.db -p 8081

• --db-name: The file name of the DB.
  • NOTE: If file.db does not exist. it will be created as a BoltDB file.
• --port: Port for listening on... (Default: 8080)

BoltDB Web Interface

URL Shortening Techniques

Bases

• base58: [1-9]][a-k][m-z][A-H][J-N][P-Z]
• base62: [0–9][a-z][A-Z]
• base64: [0–9][a-z][A-Z][+/]
• base64: [0–9][a-z][A-Z][-_] (URL and Filename safe)

123456789ABCDEFGH JKLMN PQRSTUVWXYZabcdefghijk mnopqrstuvwxyz
= 58 characters = base58

0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz
= 62 characters = base62

0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz+/
= 64 characters = base64

0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-_
= 64 characters = base64 (URL and Filename safe)

base62

Number of possible short URLs using base62 and No of characters:

• 6 characters short URL: 62^6 = ~56.8 billion possible URLs
• 7 characters short URL: 62^7 = ~3.52 trillion possible URLs
• 8 characters short URL: 62^8 = ~218 trillion possible URLs

base64

Number of possible short URLs using base64 and No of characters:

• 6 characters short URL: 64^6 = ~68.7 billion possible URLs
• 7 characters short URL: 64^7 = ~4.4 trillion possible URLs
• 8 characters short URL: 64^8 = ~281 trillion possible URLs

Techniques

• Short URL from random numbers
• Short URL from hashing (MD5, SHA1, SHA256)
• Short URLs from base conversion (from base10 to base62)
• Key Generation Service (KGS)

Implementated Technique

Source Code in shortener/shortener.go, function Encode:

• Add scheme to URL if not provided (http://, https://)
• Get the MD5 Hash of the URL
• Encode the Hash to Base 64 (URL and Filename safe)
• Keep the first 7 characters of the encoded string

Improvements

Technical

• ROUTER:
  • Add /delete route, to delete key-value entry
  • Add /show-all route, to show all key-value entry
• DB:
  • Make Batch Writes on Database
• ROUTER & DB:
  • Add goroutines / enable parallel execution of handlers
• CLI:
  • Add command line flag (or/and route) for accepting key-value entries from JSON/YAML file
  • Add command line flag (or/and route) for exporting key-value entris in JSON/YAML file
• TEST:
  • Unit Testing & End-to-End Testing
  • Handlers, API Endpoints, Shortener, Database, Main
• REDIRECTS:
  • Change redirect route endpoint from /redirect to /r
  • Change shorten route endpoint from /shorten to /s
  • Change HTTP Status Code 301 -> 302 (?)
  • Redirect to home page on redirection errors
• SHORTENER:
  • Change encoding to base62 or base58
  • Change shortening technique to more robust (base conversion, KGS)
  • Fix collision errors on same key (short_url), keep the next 7 characters (shift by one) -> Repeat until there is no match in DB
• CONFIG:
  • Implement accepting config file for constants and globals.
  • flag names, port, log file name, database file name, bucket name
• CACHE:
  • Cache results (minimize database reads)
  • Add Redis
  • Make reads buffered (and not transfer all contents into memory)
• FRONTEND:
  • Add frontend (Vanilla, React, Next.js, Gatsby, Tailwind) to support the backend service
• DEVOPS:
  • Add Dockerfile and containerize the application.
  • Make application a Go module/package/CLI.
  • Generate Documentation from source files.
  • Calculate required bandwidth/storage/traffic for API.
  • Deploy BoltDB with app (for persistance storage).

Features

• Short URL lifetime (24 hours)
• Count short URL clicks
• User Auth
• Quota / API Key
• Calculate