MattBayliss / Concurrenty

An experiment using C#, Microsoft.Net, the System.Collections.Concurrent library, and async await to create a multi-threaded queue processor.

Concurrenty

An experiment using C#, Microsoft.Net, the System.Collections.Concurrent library, and async await to create a multi-threaded queue processor. A full write-up of what's going on is at http://mattbayliss.com/c%23/2016/10/31/concurrent-asyncy-queues-ftw.html

Usage

This project contains a Request and Response object that can be customised to your needs. This example assumes a Renderer module that will generate thumbnails of specified record IDs. So, the Request and Response objects are very simple:

public class Request
{
    public int Id { get; set; }
}

public class Response
{
	public bool Success { get; set; }
	public string Filename { get; set; }
}

Initialise the queue processor, Renderer, with the constructor

Renderer(int threadCount, Func<Request, CancellationToken, Task<Response>> renderFunc)

threadCount: the number of threads to use. renderFunc: the function that changes a Request into a Task - so this would be the function that generates the thumbnail.

Then, to add something to the queue and wait for a response, you call the Renderer.Render function:

public async Task<Response> Render(Request request, TimeSpan timeout)

Here's an example:

public async Task<string> RenderToThumbnail(int recordId)
{
	string thumbnailPath = null;
	var renderer = new Renderer(20, RenderRequest);
	var request = new Request { Id = 123 };
	Response response = null;
	try
	{
		response = await renderer.Render(request, TimeSpan.FromSeconds(30));
	}
	catch(TimeoutException)
	{
		// timeout reached
	}

	return thumbnailPath;
}

private static async Task<Response> RenderRequest(Request request, CancellationToken ct)
{
	Console.WriteLine("{0}: Render Started", request.Id);

	// Here would be the heavy lifting of transforming a request into a response.
	// We'll just wait a random time between 2 and 20 seconds
	var random = new Random().Next(2000, 20000);
	await Task.Delay(random, ct);
	if(ct.IsCancellationRequested)
	{
		Console.WriteLine("{0}: Render cancelled", request.Id);
		return null;
	}

	Console.WriteLine("{0}: Render Finished", request.Id);

	return new Response
	{
		Filename = Path.GetTempFileName(),
		Success = true
	};

}