Category: .NET Core

Now I want to make a second strategy : the random strategy between a min and a max value. This is only to minimize the impact on the extension that uses the Random – it is good to be hidden inside. For Random Strategy it is better to re-use the Fixed Strategy – and this is the code:

using System;
using System.Threading.Tasks;

namespace NetCoreRetarderCore
{
    public class StrategyAwaitRandom : IStrategyAwait
    {
        StrategyAwaitFixed sf;
        public StrategyAwaitRandom(int min,int max)
        {
            if (min > max)
            {
                var x = min;
                min = max;
                max = min;
            }
            var random = new Random();
            var awaitTime = random.Next(min, max);
            sf = new StrategyAwaitFixed(awaitTime);
        }
        public Task<IStrategyAwait> AwaitDelayAfter()
        {
            return sf.AwaitDelayAfter();
        }

        public Task<IStrategyAwait> AwaitDelayBefore()
        {
            return sf.AwaitDelayBefore();
        }
    }
}

Also, I want to make some tests to verify the awaits. So I choose https://github.com/LightBDD/LightBDD and my tests looks like this:

using LightBDD.Framework;
using LightBDD.Framework.Scenarios;
using LightBDD.XUnit2;
using System;
using System.Threading.Tasks;
using Xunit;
[assembly: LightBddScope]

namespace NetCoreRetarderTest
{
    //https://github.com/LightBDD/LightBDD/wiki/Formatting-Parameterized-Steps

    [FeatureDescription(

   @"This will test just how 

will await a determined number of time
")]
    public partial class TestStrategyAwait
    {
        
        [Scenario]

        [Label("wait times fixed")]

        [Trait("Category", "Wait")]
        [InlineData(3)]
        [InlineData(1)]
        [InlineData(0)]
        [InlineData(-1)]

        public async Task WaitTime(int nrSeconds)

        {
           
            await Runner.RunScenarioAsync(

                    _ => When_Choosing_Fixed_Await_For_NRSECONDS_Seconds(nrSeconds),

                    _=> And_Await(),

                    _=> Then_Time_Ellapsed_Will_Be_NRSECONDS_Seconds(Math.Max(nrSeconds, 0))
                    )

                ;

        }
        [Scenario]

        [Label("wait times random")]

        [ScenarioCategory("Wait")]
        [InlineData(3,1)]
        [InlineData(1,2)]
        [InlineData(0,1)]
        [InlineData(-1,5)]

        public async Task WaitTimeRandom(int min,int max)

        {

            await Runner.RunScenarioAsync(

                    _ => When_Choosing_Random_Await_Between_MIN_And_MAX_Seconds(min,max),

                    _ => And_Await(),

                    _ => Then_Time_Ellapsed_Will_Be_Between_MIN_And_MAX_Seconds(Math.Max(min, 0),Math.Max(max,0))
                    )

                ;

        }
    }
}

 
You can find the code at https://github.com/ignatandrei/NetCoreRetarder/commits/version4_tests

Now I want to make the await configurable. To remind , first is just a random delay ( or static delay). The others are

1. Delay execution of some endpoints, based on how frequent are their uses

2. Delay execution based on headers / query string /  routes
3. Delay execution based on client IP
4. Delay execution based on the response

The best design pattern for this is Strategy  https://en.wikipedia.org/wiki/Strategy_pattern . Also, because I want to apply multiple await types ( maybe in order, maybe to compose) , a simple Command Pattern will be enough.

So, let’s see how it looks now:

using System.Threading.Tasks;

namespace NetCoreRetarderCore
{
    public interface IStrategyAwait
    {
        Task<IStrategyAwait> AwaitDelay();
    }
}

So now let’s see the implementation of a StrategyAwaitFixed

using System;
using System.Threading.Tasks;

namespace NetCoreRetarderCore
{
    public class StrategyAwaitFixed : IStrategyAwait
    {
        private readonly int milliseconds;

        public StrategyAwaitFixed(int milliseconds)
        {
            this.milliseconds = milliseconds;
        }

        public async Task<IStrategyAwait> AwaitDelay()
        {
            Console.WriteLine($"waiting {milliseconds}");
            
            if (milliseconds < 1)
                return null;

            await Task.Delay(milliseconds);
            
            Console.WriteLine($"finished waiting {milliseconds}");
            
            return null;
        }
    }
}

Now the Retarder Middleware should apply the awaiter one by one

using Microsoft.AspNetCore.Http;
using System;
using System.Threading.Tasks;

namespace NetCoreRetarderCore
{
    public class RetarderMiddleware : IMiddleware
    {
        private IStrategyAwait strategyAwait;

        public RetarderMiddleware(IStrategyAwait strategyAwait)
        {
            this.strategyAwait = strategyAwait;
        }

        public async Task InvokeAsync(HttpContext context, RequestDelegate next)
        {
            while (strategyAwait != null)
                strategyAwait = await strategyAwait?.AwaitDelay();
            
            await next(context);
            
        }
    }
}

The code from middleware extension is modified as generating a new random each time:

using Microsoft.AspNetCore.Builder;
using Microsoft.Extensions.DependencyInjection;
using System;
using System.Collections.Generic;
using System.Text;

namespace NetCoreRetarderCore
{
    public static class RetarderExtensions
    {
        public static void AddRetarder(this IServiceCollection serviceCollection)
        {
            serviceCollection
                .AddTransient<IStrategyAwait, StrategyAwaitFixed>(
                    it =>
                    {
                        var random = new Random();
                        var awaitMilliseconds = random.Next(1, 1000);
                        return new StrategyAwaitFixed(awaitMilliseconds);
                    }
                );
            serviceCollection.AddTransient<RetarderMiddleware>();
        }
        public static void UseRetarder(this IApplicationBuilder app)
        {
            app.UseMiddleware<RetarderMiddleware>();
        }

    }
}

Full Code Source at https://github.com/ignatandrei/NetCoreRetarder/commits/version3_Making_a_strategy_to_wait

Now it is the moment to start reorganizing the project to be easy to use by other programmers. I want, instead of registering the services manually, to can use .AddRetarder and .UseRetarder. So I create a new project, NetCoreRetarderCore.csproj , and move there the RetarderMiddleware . The only new thing is the extension class RetarderExtensions

using Microsoft.AspNetCore.Builder;
using Microsoft.Extensions.DependencyInjection;
using System;
using System.Collections.Generic;
using System.Text;

namespace NetCoreRetarderCore
{
    public static class RetarderExtensions
    {
        public static void AddRetarder(this IServiceCollection serviceCollection)
        {
            serviceCollection.AddTransient<RetarderMiddleware>();
        }
        public static void UseRetarder(this IApplicationBuilder app)
        {
            app.UseMiddleware<RetarderMiddleware>();
        }

    }
}

This let’s me reorganize the Startup as

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using NetCoreRetarderCore;

namespace NetCoreRetarder
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllers();
            services.AddRetarder();
        }
        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseRouting();

            app.UseAuthorization();
            app.UseRetarder();
            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });
        }
    }
}

You can find code at https://github.com/ignatandrei/NetCoreRetarder/commits/version2_reorg