Deputy Tech Challenge

by Justin Davidson

Task

Given a set of linked hierarchical 'roles', and a set of 'users' that each had a specific role,

Set the roles in a memory store
Set the users in a memory store
For a given userID, return all the users that are subordinates of the given user

Solution

This task has been written in Go and for convenience has been made into a CLI app. Two different implementations have been completed. One backed by a Postgres database, and one backed by the graph database Neo4j.
I assumed recursion was what was hoping to be seen in the solution hence the Postgres version, however I also wanted to include a Neo4j solution to show how simple it is to query a Neo4j database.

To run

git clone this repo. In a folder of your choice run

git clone https://github.com/RuNpiXelruN/deputy-challenge.git deputy-justin

..and then cd to the new folder from the command line

cd deputy-justin

If you have Go installed locally you can run go mod tidy which will download the dependencies required.

Postgres and Neo4j are run in Docker containers. To start them run,

make up

**It may take up to 30 seconds for the containers to be running.

To run using the Go runtime,

go run cmd/main.go

If you don't have Go installed, you can still run through the built binary provided within this repo (which is a lot quicker)

Three binaries have been provided. One each for OSX, Linux, and Windows environments.
To run the mac binary and view the CLI options, from the command line execute,

./deputyJD

To run the windows binary,

./deputyJD_win

To run the linux binary,

./deputyJD_linux

To seed the databases, run (using the mac binary as an example below)

./deputyJD seed

To fetch the postgres subordinates (remember to run ./deputyJD if you want to see the available commands)

./deputyJD pgGetSub --userID <someID>

To fetch the neo4j subordinates

./deputyJD neoGetSub --userID <someID>

A Makefile has been provided for convenience.
To see available make commands run,

make help

Some other useful make commands are,

make up          // starts docker containers for both neo4j and postgres
make down        // stops neo4j and postgres containers
make test        // runs unit tests
make build       // builds mac binary
make buildWin    // builds windows binary
make buildLinux  // builds linux binary

Connecting to the databases

Postgres

Once the container is running (make up), you can connect to the Postgres db with the following creds,

dbname: depchallenge 
user: postgres
pass: password
host: localhost (or 127.0.0.1)
port: 5433

** PLEASE NOTE THE PORT OF 5433 and not the usual 5432 **

Neo4j

Neo4j has a browser dashboard for viewing your database (among others, it also has the cypher-shell tool for the command line).
Once the container is running (make up), in your browser navigate to localhost:7474. If nothing loads initially the container may still be starting up. Once it loads you may be presented with a Neo4j login screen.
Login with,

username: neo4j
password: test

From there you will land on your Neo4j dashboard. Have a play around with the data (once you run the seed command from the cli ./deputyJD seed).
You can execute cypher queries in the editor at the top. A couple of basic cypher queries for you to play with are, (cmd + enter to execute commands, cmd + up arrow to scroll through command history, esc to toggle editor full screen)

match (n) return n  // returns all nodes and relationships. click on the graph tab to see the nodes interconnected and my architecture.

..and the query which returns subordinates. An example of userID=3 has been used here, but try others.

MATCH (:User {id: 3})-[:HAS_ROLE_OF]->(:Role)<-[*]-(r)-[*]-(us :User)
UNWIND [us] AS u
WITH DISTINCT u
RETURN u AS users

match (n) detach delete n // deletes all nodes and relationships.

run ./deputyJD seed to populate it once more.

Thanks!

Thanks for this challenge guys! If there's anything else you need or wanted to ask do hesitate to ask :)

Justin Davidson