Question

I have a C# app that subscribes to a topic on our messaging system for value updates. When a new value comes in, I do some processing and then carry on. The problem is, the updates can come faster than the app can process them. What I want to do is to just hold on to the latest value, so I don’t want a queue. For example, the source publishes value “1” and my app receives it; while processing, the source publishes the sequence (2, 3, 4, 5) before my app is done processing; my app then processes value “5”, with the prior values thrown away.

It’s kind of hard to post a working code sample since it’s based on proprietary messaging libraries, but I would think this is a common pattern, I just can’t figure out what it’s called…It seems like the processing function has to run on a separate thread than the messaging callback, but I’m not sure how to organize this, e.g. how that thread is notified of a value change. Any general tips on what I need to do?

Answer 1

A very simple way could be something like:

private IMessage _next;

public void ReceiveMessage(IMessage message)
{
    Interlocked.Exchange(ref _next, message);
}

public void Process()
{
    IMessage next = Interlocked.Exchange(ref _next, null);

    if (next != null)
    {
        //...
    }
}