InVision Code Challenge - Full-Stack

The assignment is to build a simple Producer/Consumer system. In this system the Generator will send a series of random arithmetic expressions, while the Evaluator will accept these expressions, compute the result and then report the solution to the Generator.

Project Requirements

At a minimum, we would like to see the following implemented:

• The Producer and Consumer as separate NodeJS services.
• The Producer generating random addition expressions of two positive integers, e.g. "2+3="
• The Consumer computing and returning the correct mathematical result for each expression it receives
• The Consumer successfully processing requests from two Producers concurrently at a rate of at least 1 req/sec from each Producer (2 req/sec in aggregate)
• The Consumer and Producer should log all messages they generate and receive.

You are free to support more than simple addition, but it is not required.

The end product should:

• Be built in strict JavaScript and run with NodeJS
• NOT rely on any external services like Redis, ZeroMQ or similar technologies
• NOT use Express (Connect is Ok)
• Include UML Activity Diagram and UML Sequence Diagram documenting the business logic
• Include Unit tests

Goals

• Support addition, subtraction, multiplication, and division
• Support positive, negative, and floating point numbers
• Follow basic HTTP REST API best practices
• Written in strict ES5 JavaScript
• Minimal code surface area
• Minimal external package dependencies (connect, body-parser, winston, and mkdirp)
• Simple and documented API
• 95%+ C0 (lines) test coverage
• 80%+ C1 (branches) test coverage

Installation

Requirements

• Node Engine: 0.12.7

Install

$ git clone https://github.com/rscheuermann/invision.git .
$ npm install

Running

Start The Consumer

The Consumer can be started with the following command:

$ npm start
---------------------------------
CONSUMER STARTED
 - Port: 3000
---------------------------------

Start A Producer

A Producer can be started with the following command:

$ npm run producer
---------------------------------
PRODUCER STARTED
 - URL: http://localhost:3000/compute
 - Reqs/sec: 10
---------------------------------

Many concurrent Producers can be started by issuing additional npm run producer commands.

Changing Requests Per Second

You can increase the number of requests/sec a Producer makes to the Consumer by setting an environment variable, like so:

$ REQS_PER_SECOND=50 npm run producer
---------------------------------
PRODUCER STARTED
 - URL: http://localhost:3000/compute
 - Reqs/sec: 50
---------------------------------

Viewing Logs

The consumer logs requests and responses to the logs/consumer.log file:

$ tail -f logs/consumer.log
2015-08-09T11:57:22.383Z - info: REQUEST  "POST /compute HTTP/1.1" -     - [7.38 * 5.05 = ]
2015-08-09T11:57:22.384Z - info: RESPONSE "POST /compute HTTP/1.1" - 200 - [7.38 * 5.05 = 37.269]

The producers log requests and response to the logs/producer.log file:

$ tail -f logs/producers.log
2015-08-09T11:57:22.382Z - info: REQUEST  "POST http://localhost:3000/compute" -     - [7.38 * 5.05 = ]
2015-08-09T11:57:22.384Z - info: RESPONSE "POST http://localhost:3000/compute" - 200 - [7.38 * 5.05 = 37.269] 3ms

Unit Tests

Running Tests

$ npm test
    
    48 passing (2s)

Running Code Coverage Report

$ npm run coverage
=============================== Coverage summary ===============================
Statements   : 96.91% ( 157/162 )
Branches     : 89.74% ( 35/39 )
Functions    : 90% ( 27/30 )
Lines        : 96.91% ( 157/162 )
================================================================================

REST API

Compute

Computes the result of a mathematical expression in the form "x + y = "

Addition:

 1 + 2 = 

Subtraction:

 2 - 1 = 

Multiplication:

 1 * 2 = 

Division:

 1 / 2 = 

Positive, negative, and floating point numbers are supported

• URL

  /compute

• Method:

  POST

• Data Params

• Content-Type: text/plain

• Content: 1 + 2 = - Math expression to evaluate

• Success Response:

  • Code: 200
    Content: 1 + 2 = 3

• Error Response:

  • Code: 400 BAD REQUEST
    Content: 1+2` must be in the form of a math expression, e.g. `2+3=

  OR

  • Code: 405 METHOD NOT ALLOWED
    

  OR

  • Code: 406 NOT ACCEPTABLE
    

• Sample Call:

    agent.post({
            url: 'http://localhost/compute,
            headers: {
                'Content-Type': 'text/plain'
            },
            body: '2 + 3 = '
        });

UML Activity Diagram

UML Sequence Diagram