URL Lookup

Problem

A website is using so-called “pretty” URLs to give users and bots a good impression of what the page is about, e.g.

- http://www.example.com/Clothing/Women/
- http://www.example.com/Fashion/

All these combinations are mapped in a table with the following format:

All these combinations are mapped in the following format:

From:                                    To:
/products                                /Fashion/
/products?gender=female                  /Women/
/products?tag=5678                       /Boat-Shoes/
/products?gender=female&tag=123&tag=1234 /Women/Shoes/
... ...
/products?brand=123                      /Adidas/

You can see it as a key-value map between combinations of strictly ordered parameters and pretty URLs. Use cases for this mapping table are the lookup of a parameter combination as soon as you request a pretty URL and a reverse lookup of the pretty URL, whenever you are building a link.

Your task:

1. Please implement scaling and performant service in Java to look up URLs in both ways (bi-directional lookup). When you are building a link and you can’t find an exact match, use the one that matches best (covers the biggest part of the URL from left to right):

You are building a link for the following parameter combination:

 /products?gender=female&tag=123&tag=1234&tag=5678

The mapping table doesn’t contain an exact match for it, so the best match would be:

 /Women/Shoes/?tag=5678

2. Please expose your service in a RESTful API with 2 endpoints, one of them receives a list of parameterized URLs and returns a list of corresponding pretty URLs, the other one receives a list of pretty URLs, and returns a list of corresponding parameterized URLs. Use a common framework for your business logic.

Prerequisite

• Java 11 (Version - 11.0.11)
• Maven (Version - 3.6.3)

Build & Run

Extract the zip file and go to the directory 'url-lookup'.

There is two ways to build & run the project.

1st way:

Run the following command from projects root directory to build it-

mvn clean install

Then go to target directory & run the command to run it:

java -jar url-lookup-0.0.1-SNAPSHOT.jar

2nd way:

Run the following command from projects root directory to build & run -

mvn spring-boot:run

NB - it may take time for dependency downloading.

Test

After building, the application will run on port 8080.

I've used curl from cygwin terminal to test the project. Two api is exposed - /api/lookup/pretty-url takes parameterized urls as input & return pretty urls as output whereas /api/lookup/param-url takes pretty urls as input & return parameterized urls as output.

Test case 1:

$ curl -i -H "Accept: application/json" -H "Content-Type:application/json" -X GET --data '{"inputUrls":["/products", "/products?gender=female", "/products?tag=5678", "/products?gender=female&tag=123&tag=1234", "/products?brand=123"]}' "http://localhost:8080/api/lookup/pretty-url"

Output:

{"results":["/Fashion/","/Women/","/Boat-Shoes/","/Women/Shoes/","/Adidas/"]}

Test case 2:

$ curl -i -H "Accept: application/json" -H "Content-Type:application/json" -X GET --data '{"inputUrls":["/products", "/products?brand=123", "/products?gender=female&tag=123&tag=1234&tag=5678"]}' "http://localhost:8080/api/lookup/pretty-url"

Output:

{"results":["/Fashion/","/Adidas/","/Women/Shoes/?tag=5678"]}

Test case 3:

$ curl -i -H "Accept: application/json" -H "Content-Type:application/json" -X GET --data '{"inputUrls":["/products", "/notlisted?tag=456"]}' "http://localhost:8080/api/lookup/pretty-url"

Output:

{"results":["/Fashion/","/notlisted?tag=456"]}

Test case 4:

$ curl -i -H "Accept: application/json" -H "Content-Type:application/json" -X GET --data '{"inputUrls":["/Fashion/","/Women/","/Boat-Shoes/","/Women/Shoes/","/Adidas/"]}' "http://localhost:8080/api/lookup/param-url"

Output:

{"results":["/products","/products?gender=female","/products?tag=5678","/products?gender=female&tag=123&tag=1234","/products?brand=123"]}

Test case 5:

$ curl -i -H "Accept: application/json" -H "Content-Type:application/json" -X GET --data '{"inputUrls":["/Women/", "/Women/Shoes/","/Women/Shoes/Addidas"]}' "http://localhost:8080/api/lookup/param-url"

Output:

{"results":["/products?gender=female","/products?gender=female&tag=123&tag=1234","/products?gender=female&tag=123&tag=1234&tag=Addidas"]}

Test case 6:

$ curl -i -H "Accept: application/json" -H "Content-Type:application/json" -X GET --data '{"inputUrls":["/Fashion/","/NotAvailable"]}' "http://localhost:8080/api/lookup/param-url"

Output:

{"results":["/products","/NotAvailable"]}

Framework & Libraries

• Spring framework
• H2 in-memory database (for simplicity I've used it, but in production environment, it must be RDBMS)
• Ehcache (for simplicity I've used it, but in production environment, I prefer Redis)
• JPA + Hibernate

How it works?

• 1st of All, its a spring boot application, when it runs it first run script (src/main/resources/data.sql) to insert url mappings in database. I have assumed that in production, the mapped urls should be stored in any relational database like MySQL/PostgreSQL and don't need to run script.
• 2nd, it initialize ehcache and created a cache region with name url_cache, configuration located in resources directory. In production environment it should be redis cache which run standalone and independently. And multiple instance of this service will access same cache server if needed in scalable environment.
• 3rd, I've added a custom configuration which run once and load all mapped url from database to cache. I didn't write much logic here as it's not main requirement but in reality may be data need to update, in that case cron job will be added instead of this which will run as desired time. As both way mapping possible, so I put pretty as key and param urls as value & vice versa.
• Now, system has data in cache which is very fast to access in terms of access from database.
• Next, when an api hit, it load desired services which handle mapping lookup separately.
• When list of url provides, it first check whole url in cache, if found then it load url in list. If not, then, it exclude the last part (for example pretty-url /Women/Fashion/Addidas/ input, it should exclude Addidas/ and try to find /Women/Fashion/ in cache) and continue until find one. For param urls it exclude last tags (for example - /products?tag=125&tag=589, it exclude tag=589 at first and try to find in cache /products?tag=125 and continue until find one). System try to find best match, if not found, then original url should be return.

NB

• Important factor here, I have used cache for lookup, because for best matching I've to lookup many times for one input url. So, cache server (redis, for simplicity I've used ehcache here) should have all url and will never expire. Cache server will be center of data lookup and all instances will access it for faster delivery instead of searching in database.
• Unit test - which is very important buy I didn't write unit test for time constraint. As time is very limited, so I didn't get chance to write any unit test.