Punchclock: A library for managing concurrent operations

Punchclock is the low-level scheduling and prioritization library used by Akavache to orchestrate pending concurrent operations.

What even does that mean?

Ok, so you've got a shiny mobile phone app and you've got async/await. Awesome! It's so easy to issue network requests, why not do it all the time? After your users one-:star2: you for your app being slow, you discover that you're issuing way too many requests at the same time.

Then, you try to manage issuing less requests by hand, and it becomes a spaghetti mess as different parts of your app reach into each other to try to figure out who's doing what. Let's figure out a better way.

So many words, gimme the examples

var wc = new WebClient();
var opQueue = new OperationQueue(2 /*at a time*/);

// Download a bunch of images
var foo = opQueue.Enqueue(1, 
    () => wc.DownloadFile("https://example.com/foo.jpg", "foo.jpg"));
var bar = opQueue.Enqueue(1, 
    () => wc.DownloadFile("https://example.com/bar.jpg", "bar.jpg"));
var baz = opQueue.Enqueue(1, 
    () => wc.DownloadFile("https://example.com/baz.jpg", "baz.jpg"));
var bamf = opQueue.Enqueue(1, 
    () => wc.DownloadFile("https://example.com/bamf.jpg", "bamf.jpg"));

// We'll be downloading the images two at a time, even though we started 
// them all at once
await Task.WaitAll(foo, bar, baz, bamf);

Now, in a completely different part of your app, if you need something right away, you can specify it via the priority:

// This file is super important, we don't care if it cuts in line in front
// of some images or other stuff
var wc = new WebClient();
await opQueue.Enqueue(10 /* It's Important */, 
    () => wc.DownloadFileTaskAsync("http://example.com/cool.txt", "./cool.txt"));

What else can this library do

• Cancellation via CancellationTokens or via Observables
• Ensure certain operations don't run concurrently via a key
• Queue pause / resume