Serve APIs returning & consuming observable streams over WebSockets using .NET
Think of it as ASP.NET Web API but with controllers which return IObservable<T> instead of Task<T>, which allows you to easily push to clients. Controllers can also consume IObservable<T> parameters, see the ChatController example.
SignalR is great for a lot of realtime applications which scaleout easily, but it's not easy to create realtime apps which require authoritative logic - take a game for example, or other complex apps. This is perhaps because SignalR gives you transparent scale-out, so the rendezvous point for notifications (Service Bus, SQL Server, etc) does not contain application logic.
Instead, WebStreams does not give you transparent scale-out at all. Scale-out can easily be achieved using Service Bus or another backplane like in a SignalR app, but often scale-out will sit in Microsoft Orleans or another Actor framework. Another option for scale-out is Azure Event Hubs, which can contain application logic.
See the WebStreamSamples repository for a sample server with a Web client.
TODO: publish sample which scales out app logic using Microsoft Orleans.
PM> Install-Package WebStreams.Server
NuGet will pull in all dependencies (Owin, Json.NET, Rx).
Call UseWebStream() in your OWIN startup method. See below for an example.
StockController.cs
[RoutePrefix("/stock")]
public class StockTickerController
{
private readonly ConcurrentDictionary<string, IObservable<Stock>> stocks =
new ConcurrentDictionary<string, IObservable<Stock>>();
[Route("ticker")]
public IObservable<Stock> GetTicker(string symbol)
{
return this.GetStockTicker(symbol);
}
private static IObservable<Stock> CreateStockTicker(string symbol)
{
var random = new Random();
// Construct a shoddy, pseudo-random walk.
return
Observable.Interval(TimeSpan.FromSeconds(0.1))
.Select(time => random.NextDouble())
.Scan((double)random.Next(1000), (prev, randomVal) =>
Math.Max(0, prev * (1 + (0.01 * (randomVal - 0.5)))))
.Select(val => new Stock(symbol, val, DateTime.UtcNow));
}
private IObservable<Stock> GetStockTicker(string symbol)
{
return this.stocks.GetOrAdd(symbol, CreateStockTicker);
}
}In your OWIN Startup.cs
public void Configuration(IAppBuilder app)
{
app.UseWebStream();
}