README.md

Distinct Queue Processor

The indexed multi-thread queue.

This library was built to manage a large queue of long running parallel processes. Parallelization is easily configured and threading is managed internally. The queue is indexed in a library for fast lookups of running tasks, and to provide the ability to reject items which are already in queue.

Nuget Packages

Package Name	Target Framework	Version
DistinctQueueProcessor	.NET Standard 2.0

Usage

The main contents of this library are in a single abstract class, DQP.DistinctQueueProcessor<T>. Create your own derivative class which overrides the following required methods:

• Process(T item)
  • Do your work here. This method is run on a threaded task.
• Error(T item, Exception ex)
  • Called when an exception is caught from Process(T item). Throwing an exception here will kill the running worker so take care.

Also provided is an wrapper which takes Actions in the constructor. See the examples below for more detail.

Inheritance Example

Create a new class inheriting from DistinctQueueProcessor<T> where T is the type of object you want to enqueue.

class DqpExample : DistinctQueueProcessor<string>
{
    protected override void Error(string item, Exception ex)
    {
        Console.Error.WriteLine(ex.ToString());
    }

    protected override void Process(string item)
    {
        // This will be run on a thread, so don't be surprised if messages print out-of-order.
        Console.WriteLine(item);
    }
}

You'd then use your class as follows:

var example = new DqpExample();
example.AddItem("Hello, world!");

Action Example

If inheriting from DistinctQueueProcessor in a custom class is too heavy for your use case, ActionQueue can be used instead. It's a simple wrapper around the base class which takes two action as constructor parameters.

var actionQueue = new ActionQueue<string>(
	new Action<string>(x =>
	{
		Console.WriteLine(item);
	}),
	new Action<string, Exception>((x, ex) =>
	{
		Console.Error.WriteLine(ex.ToString());
	}));
    
actionQueue.AddItem("Hello, world!");

Gotchas

Internally the queue is indexed using a Dictionary<string, T>, where the key is T.ToString(). Ensure your T has a ToString implementation which returns short unique values.