Retarder – Making a strategy to wait–part 3

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