C# Round Robin Resources

The Problem:
You have scarce / limited resources and you want to use these in and efficient way in your Code. E.g. You can only create N objects of certain class because of its limitation in terms of Resources or Licenses, and you want to share those Objects across M Consumers.

The Solution:
One way is to use Round Robin scheduling, and in this post I’ll show you how to do that.

Let’s say we have a class ScarceResource which can only be instantiated 3 times in a program. As an example our class generates Random numbers.

public class ScarceResource
{
	private Random _random;
	private string _name;
	
	public ScarceResource(string Name)
	{
		_name = Name;
		_random = new Random();
	}

	public ScarceResource(string Name, int seed)
	{
		_name = Name;
		_random = new Random(seed);
	}

	public string GetRandomNumber()
	{            
		return _name + ":" + _random.Next().ToString();
	}
}

RoundRobinList class will handle Round Robin Scheduling

public class RoundRobinList
{
	private readonly IList _list;
	private readonly int _size;
	private int _position;
	private object _lock;

	public RoundRobinList(IList list)
	{
		if (!list.Any())
			throw new NullReferenceException("list");

		_list = new List(list);
		_size = _list.Count;
		_position = 0;
		_lock = new object();
	}

	public T Next()
	{
		if (_size == 1)
			return _list[0];

		lock (_lock)
		{
			if (_position == _size)
			{
				_position = 0;
			}
			return _list[_position++];
		}
	}
}

Below is a sample Console Program which instantiate 3 Objects of ScarceResource and Use these Objects in Round Robin fashion to Generate Random Numbers.

class Program
{
	static RoundRobinList rrList;
	static bool keepRunning = true;

	static void Main(string[] args)
	{
		Console.CancelKeyPress += delegate(object sender, ConsoleCancelEventArgs e)
		{
			e.Cancel = true;
			keepRunning = false;
		};

		// Create Objects and add to List
		List list = new List();
		list.Add(new ScarceResource("Object 1", 8767));
		list.Add(new ScarceResource("Object 2", 12323));
		list.Add(new ScarceResource("Object 3", 1214));

		// Create Round Robin List and Add Objects List to it
		rrList = new RoundRobinList(list);

		while (keepRunning) 
		{
			Process();
			System.Threading.Thread.Sleep(1000);
		}
	}

	public static async Task Process()
	{
		await Task.Run(() => Console.WriteLine(rrList.Next().GetRandomNumber()));
	}
}