Distributed Armstrong Numbers

The goal of this prototype is a simpliest implementation of distributed Armstrong Numbers (or whatever else) calculation using few workers and a queue.

Disclaimer:

1. It's a prototype. The idea is to make things work, not make them reusable.
2. It's a prototype. I didn't write tests for it. The idea is to do a little as possible to make it work.
3. It's a prototype. No failover or proper exception handing is in place.
4. There is no configuration - code assumes it works with localhost only. Because... it's still a prototype.
5. It's possible to design the code better. For example, Generator should know nothing about RabbitMQ. But - see #1.

Solution description

I've implemented two modules: Manager and Worker which use a distributed queue software (RabbitMQ) to communicate.

A 'Manager' sends the lengths of Armstrong Number it wants to be generated to a queue called Nquque. For example:numbers from 1 to 19. Then it stars listening for a queue called ArmstrongNumbers and prints out everything it reads from the queue.

There could be a few Workers launched. Each listens for the Nqueue queue. Once a number is available - a Worker calculates Armstrong numbers of the required length and once found put them to the ArmstrongNumbers queue.

Setup

First of all it's needed to setup RabbitMQ. It's easy and well described at: their site. I used Homebrew at my Mac.

brew update
brew install rabbitmq
/usr/local/sbin/rabbitmq-server

Then you may check if it works by link: http://localhost:15672/. Simple interface allows to create a queue and publish messages there.

Compile and run Worker and Manager classes. The following RabbitMQ client lib is used: com.rabbitmq:amqp-client:3.6.2. First of all you may run a few Workers and then one Manager that will immidiately makes things run.

Code structure

The code is divided to three files:

1. Generator.java - is responsible for Armstrong Number calculations and throwing them to the queue. The calculation algorithm is described here. It uses BigInteger, while it would also be possible to execute specific algorithm depending of the size of the numbers which needs to be calculated.
2. Worker.java - uses Generator.java class and works with the relevant queues. It has a main method.
3. Manager.java - works with the relevant queues and prints the results to the console. It has a main method.

It's very good described here how to work with RabbitMQ client in Java.