Architecture:

Key points

• No length restriction

  • There should be no limit on URL length. For that puspose not using inbuild URL_FIELD feature , because most of them provide support upto 200 char limit and some upto 1000. so we will receive free text from user and validate url on server end.

• Avoid losing url from formatter

  • Almost all formatter target non-alphanumeric value for formatting. In order to avoid this issue we will generate hashed_url with only alphanumeric values.

• Link Tracker

  • We will also manage no of times user clicked the valid short url .

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APPROCH 1

https://HOST_NAME/<short_hash_string>

1. Basic idea is to generate random short_hash_string string of length (6)
2. Check if
   • this short_hash_string is not present in DB then insert short_hash_string into DB with actual_url mapping with hit_count=0.
   • If this short_hash_string is present , repeat step 1

Limitation on this approch

for every new request we have look over DB to check wether currently generated string is present in DB or not which is not efficent if try to scale it.

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APPROCH 2 (Applied on this project):

https://HOST_NAME/<short_hash_string>

For this project length of short_hash_string is >=1 and <=6

This is the respresentation of our schema

ID	actual_url	short_hash_string	hit_count
1	https://www.youtube.com/	hash1	0
2	https://www.youtube.com/	hash2	2
n	nth_URL	nth_hash	102

There are 62 alphanumeric charactor and x is one of alphanumeric charactor
short_hash_string  combinations
x                  = 62   
xx                 = 62*62 = 3844 
xxx                = 62*62*62 = 246016 
xxxx               = 62*62*62*62 = 15252992 
xxxxx              = 62*62*62*62*62 = 945685504  
xxxxxx             = 62*62*62*62*62*62 = 58632501248  

-We can provide diffrent url upto 58632501248 (sum of above combination) if we just insert (short_hash_string --> actual_url) mapping without looking for short_hash_string in DB and just increment the primary key ID.

- Now our problem shorten to 'generate a unqiue hash for a interger' and 'from this generated unique_hash i can revert back to integer'.

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Function Description

We can use the concept of base conversion . click here to learn more about base conversion.

Functions description:

• getIdFromHash : params: get 1 param "string" consist of alphanumeric chars with size from 1 to 6 return a integer value

• getHashValueFromId : params: get one param "int" can be any ineger between 1-69809999936 return: return a hashed value

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SYSTEM FLOW:

• WHEN CLIENT WANT TO GET SHORTEN URL

  1. client send a url_short request to server

  2. server first get the last row from data in order to extarct id from it.

     • if there is no row then ID = 1
     • else ID =last_id +1

  3. Then it call getHashValueFromId() and it will generate a hashed url

  4. Save it to datebase ( ID , actual_url , short_hash_string)

• WHEN CLIENT WANT TO CLICK ON SHORTEN URL

  1. Client clicked on hashed_url.
  2. Server call getIdFromHash() and retrive id corresponding to the hashed_url.
  3. Then server hit database in-order to find the row with primary_key = id.
     • if there is no row in DB - Then we return the BAD_REQUEST ERROR or Redirect user to invalid-url page In that case either shorten_url already used or no row in inserted for the requested id.
     • else
       • we receive the matched row.
         • increase hit_count by 1
  4. Now we have matched row , retrive actual url
  5. Delete entry for this id from database
  6. Redirect the user to actual url.