4 : Signals R gr8

Random fact

You won't believe where McDonald's opened its first drive-thru - Soldiers at Fort Huachuca (Sierra Vista’s) were not allowed to appear in public in their work or duty uniforms, a longstanding rule that had to do with military decorum, according to Steve Gregory, a technician at the Fort Huachuca Museum.

Instead, he pushed out a small portion of the wall, creating just enough space for an attendant. He installed a small sliding window, low enough to be reached via car window, wide enough to pass burgers and a side of fries.

On Jan. 24, 1975, the world’s largest fast-food franchise opened its first drive-through.

Introduction

• What is SignalR
  • Add real-time functionality to your dashboards, maps, games and more. What is real-time functionality? It's the ability to have your server-side code push content to connected clients as it happens, in real-time.
  • http is a stateless one way protocol - SignalR changes that in a way
  • Duplex / two way communication
• Is it a new thing?
  • Been out since at least 2013, builds on existing web technologies
  • Other eco systems do have support for web sockets and long polling
  • SignalR provides a nice developer experience with low barrier to entry and nice abstractions in the form of Hubs, Clients etc
• What have you used it for
  • Comparison platform - retrieving quotes from many external providers, where each provider will come back at different times.
    • SignalR great to update the UI when all quotes have returned
    • Aggregation operations like min price, number of providers quoted etc
    • Used with a Vue client - JS client npm package worked well inside Vue
  • Admin interface - client used as an event handler off the back of quote requests to provide real-time view of what quotes were being requested, to broadcast to other clients to update dashboards etc
• Only for .net languages?
  • .NET client
  • Java client
  • JavaScript client - now an npm package
• Where can it be used
  • Web app
  • Console app
  • Windows Service / daemon (linux)
  • Excel
  • Cross platform
• But it needs newer tech doesn't it?

  • Browser versions supported - IE, Edge, Chrome, Safari, Mobile

  • Communication channels

    • HTML 5 transports
      • Websockets - ideal
      • Server Sent Events - server push over http

    Commet transports (long-held http requests)

    • Ajax Long polling
    • Forever Frame (IE only) - hidden iframe making request to server that does not complete, but server sends script to client which is immediately executed
• Infrastructure requirements
  • Do you need extra servers
    • For server farm environments
      • Need to enable session affinity (sticky sessions) on ARRs, load balancers
      • Need to use a SignalR Backplane if you want to broadcast to all clients -
        • Need to replace default IMessageBus which only knows about local machine
        • Currently provides 3 backplanes:
          • Azure Service Bus
          • Redis
          • Sql server
        • simple to setup - install nuget package, configure connection etc in Startup.cs
          • Microsoft.AspNet.SignalR.ServiceBus Microsoft.AspNet.SignalR.StackExchangeRedis Microsoft.AspNet.SignalR.SqlServer
          • GlobalHost.DependencyResolver.UseServiceBus(connectionString, "YourAppName"); GlobalHost.DependencyResolver.UseStackExchangeRedis("server", port, "password", "AppName"); GlobalHost.DependencyResolver.UseSqlServer(sqlConnectionString);
  • Azure SignalR Service - simplifies ARR config and takes care of the backplane for you
• Can it cope with thousand of users?
  • Very efficient and scales well by default
  • Might need to tune web server / ASP.NET to support an increased number of concurrent connections
    • tweaking IIS config - Max Concurrent Requests per app
    • teaking ASP.NET config - Maxium Concurrent Requests Per CPU, Request Queue Limit
  • See performance page on the SignalR wiki on Github
• Communication protocol
  • SignalR is open-source on GitHub, just like the rest of .NET. In addition to the source code, the protocol specification for communication between hubs and clients is open too.

OS project/utility of the week

We had a few this week...

Polly (http://www.thepollyproject.org/) quality logo :-)

express resilience and transient fault handling policies like:

• Retry, Circuit Breaker, Timeout, Bulkhead Isolation, Fallback
• lovely fluent policy declaration api

FluentDocker (https://github.com/mariotoffia/FluentDocker)

Basically allows you to build up docker containers using a fluent syntax. For example...

ngrok (https://ngrok.com/docs) - One command for an instant, secure URL to your localhost server through any NAT or firewall.