Similarly to other social networks like Facebook or LinkedIn, XING allows users to connect with each other. To facilitate networking, XING provides contact recommendations (see for example: xing.com/network - Grow your network today):
2nd-degree contacts play an important role in this recommender system. The intuition behind this is: The friends of my friends are also my friends.
As part of this assignment, we would like to develop a service that provides the following functionalities:
- a method for storing contacts of a user (in-memory)
- a method for retrieving the contacts of the user's contacts
These endpoints should be made available via the following two endpoints.
This endpoint allows for storing the contacts of the given user (user_id) and should work as follows:
curl -XPOST --header "Content-Type: application/json" \
--data '{"contacts":[2, 3, 4, 5]}' \
'http://localhost:9000/user/1/contacts'
With the request above, we would store (overwrite) the contacts of user 1. The data should be stored in-memory and forms the basis for the second endpoint.
This endpoint returns the second-degree contacts of the given user (user_id), i.e. the contacts of the user's contacts.
Example: Imagine that the following contact data is already stored.
| user_id | contacts |
|---|---|
| 1 | [2, 3, 4, 5] |
| 2 | [1, 6, 8] |
| 3 | [1, 4] |
| 4 | [1, 3] |
| 5 | [1, 6] |
| ... | ... |
Given this data, we would expect the following response:
curl -XGET 'http://localhost:9000/user/1/sd-contacts'
Expected response:
[6, 8]
Hence, /user/:user_id/sd-contacts should only return 2nd-degree contacts: Direct contacts of the user (e.g. user 3 and 4) as well as the user herself (e.g. 1) should not be returned.
In order to test your service, you can use the test data that is given in contacts.tsv. This file has two columns:
| Column | Description |
|---|---|
user_id |
the ID of the user |
contacts |
the contacts of the corresponding user in the JSON format that is expected by POST /user/:user_id/contacts |
We also provide a Jmeter file (jmeter-test.jmx) which you can use to test your service, but you are free to create your own scripts for evaluating your service.
- You can develop the corresponding service either in Scala or Java.
- The service should be designed to be fast and should also work in case there are concurrent requests.
- We do not expect a sophisticated solution, but we expect that you can justify your design decisions thoroughly.
- In a next meeting, we would like to discuss your solution. Please push your code and descriptions before the meeting :-)