/talks-10-alternatives-to-akka

10 Alternatives to Akka.net available to .net developers now, when to use, and when to choose akka.

Primary LanguageC#MIT LicenseMIT

objectives

code walk through of circuitbreaker and actor supervision with Akka.net and (without akka) using Polly

time permitting show a few of these in code

  • Polly
  • MediatR
  • Memstate

what are we going to simulate?

  • car insurance quote finder. A "panel" of API's to get the best quote. // panel.txt
  • for our demo we'll start 20 services, so that some can hang, and block, all services reliability is independant of the others.

Will demonstrate implementing circuit breaker on both Akka.net vs non akka and Polly running as the system starts, by telling an actor to become OFFLINE until all the upstream services are online, and monitoring the upstream services. If more than 2 upstream services go offline, then the monitoring actor tells the QuoteManager actor to become OFFLINE again. And ONELINE when enough upstream services are online.

  • I will attempt to simulate multiple providers experiencing different types of technical difficulties based on a Chance of experiencing difficult that is configured. A list of quote providers configured as so in panel.json...
    ...
    {
      "Name": "Hitchcock Investments",
      "Speed": 700,
      "Port": 5117,
      "Availability": "Bad"
    },
    ...

Availability of each of the demo services is either Excellent, Good, Spotty and Bad. The console app QuotePanel launches one self hosted webapi per entry in the panel file, at the configured port, with the configured speed and availability.

The demo QuoteService is a self hosted .NET Core 3 app, in QuoteService. The logic for the demo is in Controllers/QuoteController.cs and the chance of an api request throwing one of the errors defined above is defined as so

        private bool Should()
        {
            switch(_availability)
            {
                case Availability.Excellent: return false;
                case Availability.Good: return (_rnd.Next(100) > 10);
                case Availability.Average: return (_rnd.Next(100) > 30);
                case Availability.Spotty: return (_rnd.Next(100) > 50);
                case Availability.Bad: return (_rnd.Next(100) > 90);
                default: return false;
            }
        }

This impacts the % likelihood that a request to any Insurance company in our panel will give us one of these problems;

  - 429 with  Retry-After 
  - 503 Service Unavailable, a retry should succeed.
  - 404 should return 404 `Not found`, a retry should never succeed.
  - 500 should return 500 `Internal server error`, possibly take the service down permanently.

I have written a rudimentary BackoffSimulator.cs that will send 429's and take the service offline until a set time has past. (fingers crossed this gives us the behavior we want for the demo.)

To save time I am using Konsole, to rapidly mock up a console user interface. (currently the UX library only works on windows because .NET console has not been fully ported to .NET standard yet, volunteers anyone?)

var w = new Window();
var left = w.SplitLeft();
var backlog = left.SplitTop('backlog');
var current = left.SplitBottom('current');
var quote = right.SplitTop('quote panel');
var status = right.SplitBottom('status');
...
foreach(var rfq in rfqs) { backlog.WriteLine(rfq.ToString()); }
....

... gives us the following type of scrolling windowed console UX for the test code

This is the architecture for the actors used in the demo so far. I will try to keep this updated as I work on the project.

Support, Feedback, Suggestions

Please drop me a tweet if you find this demo code useful as a framework for your own experiments and learning.

keep chillin!

O__
_/`.\
    `=(

Alan

p.s. join us at snowcode 2019!
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Alan Hemmings