xperiandri / bayeux-client-dotnet

Bayeux events client for .NET

.NET Bayeux Client

Bayeux is a protocol that enables web-friendly message transport over HTTP, WebSockets, etc.

This library provides a client for receiving events from a Bayeux server, through the HTTP long-polling transport, or WebSockets. It provides convenient async methods.

Quick start

This is an example of usage:

var httpClient = new HttpClient();
var bayeuxClient = new BayeuxClient(
    new HttpLongPollingTransportOptions()
    {
        HttpClient = httpClient,
        Uri = "http://localhost:8080/bayeux/",
    });

bayeuxClient.EventReceived += (e, args) =>
    Debug.WriteLine($"Event received on channel {args.Channel} with data\n{args.Data}");

bayeuxClient.ConnectionStateChanged += (e, args) =>
	Debug.WriteLine($"Bayeux connection state changed to {args.ConnectionState}");

bayeuxClient.AddSubscriptions("/**");

await bayeuxClient.Start();

Logging

Logger name is Genesys.Bayeux.Client.

Logging levels used are:

• Debug: Contents of messages.
• Info: Messages about connection availabity and other significant infrequent messages.
• Warn: Recoverable errors. For example, connection errors with reconnection strategy.
• Error: Unexpected errors.

This library uses LibLog for logging. It will automatically adapt to NLog, Log4Net, Serilog and Loupe.

You may also provide your own custom logger implementation by calling:

Genesys.Bayeux.Client.Logging.LogProvider.SetCurrentLogProvider(<My ILogProvider implementation>);

If none of these are available, System.Diagnostics.TraceSource will be used. (See how to configure tracing).

Features

Start modes

Different applications need different ways to start a Bayeux connection.

Some applications may want to wait and check if the first connection succeeds. This is typical for interactive user applications. For this case, use method Start(CancellationToken).

Other applications, like the ones running in the background, may continue to run with an failed first connection, as long as reconnections are tried. For this case, use method StartInBackground().

Connection and subscription recovery

Reconnections and automatic channel re-subscriptions are implemented.

Reconnection delays can be provided as a parameter of the BayeuxClient constructors.

Subscription modes

Usually, applications can't recover from a failed subscribed channel, and they can't control when the connection is available anyway. These applications use the AddSubscription and RemoveSubscription methods.

Picky applications that want to make sure that subscriptions are successful use the Subscribe and Unsubscribe methods.

WebSockets

WebSocket transport is supported:

var bayeuxClient = new BayeuxClient(
    new WebSocketTransportOptions()
    {
        Uri = new Uri("ws://localhost:8080/bayeux/"),
    });

Customizing HTTP POSTs

The IHttpPost interface is offered for clients that want to provide their own HTTP POST implementation. This is also useful to implement retries for servers that may occasionally fail, in need of a session refresh.

TaskScheduler for event publishing

It is important to publish events in the proper threading context, for not running into obscure multithreading issues.

By default, a proper scheduler will be chosen, based on the current SynchronizationContext. This will do the right thing for Windows Forms or WPF applications. If there is no current SynchronizationContext, a TaskScheduler with ordered execution of events will be created and used.

The client can also provide a TaskScheduler as a parameter to BayeuxClient constructors.