FailingMiddleware for Ordering API

Author: eiximenis

src/Services/Ordering/Ordering.API/Infrastructure/Middlewares/FailingMiddleware.cs

@@ -0,0 +1,79 @@
+using Microsoft.AspNetCore.Http;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace Ordering.API.Infrastructure.Middlewares
+{
+    public class FailingMiddleware
+    {
+        private readonly RequestDelegate _next;
+        private bool _mustFail;
+        private readonly FailingOptions _options;
+        public FailingMiddleware(RequestDelegate next, FailingOptions options)
+        {
+            _next = next;
+            _options = options;
+            _mustFail = false;
+        }
+        public async Task Invoke(HttpContext context)
+        {
+            var path = context.Request.Path;
+            if (path.Equals(_options.ConfigPath, StringComparison.OrdinalIgnoreCase))
+            {
+                await ProcessConfigRequest(context);
+                return;
+            }
+
+
+            if (_mustFail)
+            {
+                context.Response.StatusCode = (int)System.Net.HttpStatusCode.InternalServerError;
+                context.Response.ContentType = "text/plain";
+                await context.Response.WriteAsync("Failed due to FailingMiddleware enabled.");
+            }
+            else
+            {
+                await _next.Invoke(context);
+            }
+        }
+
+        private async Task ProcessConfigRequest(HttpContext context)
+        {
+            int i = 0;
+            var enable = context.Request.Query.Keys.Any(k => k == "enable");
+            var disable = context.Request.Query.Keys.Any(k => k == "disable");
+
+            if (enable && disable)
+            {
+                throw new ArgumentException("Must use enable or disable querystring values, but not both");
+            }
+
+            if (disable)
+            {
+                _mustFail = false;
+                await SendOkResponse(context, "FailingMiddleware disabled. Further requests will be processed.");
+                return;
+            }
+            if (enable)
+            {
+                _mustFail = true;
+                await SendOkResponse(context, "FailingMiddleware enabled. Further requests will return HTTP 500");
+                return;
+            }
+
+            // If reach here, that means that no valid parameter has been passed. Just output status
+            await SendOkResponse(context, string.Format("FailingMiddleware is {0}", _mustFail ? "enabled" : "disabled"));
+            return;
+        }
+
+        private async Task SendOkResponse(HttpContext context, string message)
+        {
+            context.Response.StatusCode = (int)System.Net.HttpStatusCode.OK;
+            context.Response.ContentType = "text/plain";
+            await context.Response.WriteAsync(message);
+        }
+
+    }
+}

src/Services/Ordering/Ordering.API/Infrastructure/Middlewares/FailingMiddlewareAppBuilderExtensions.cs

@@ -0,0 +1,23 @@
+using Microsoft.AspNetCore.Builder;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace Ordering.API.Infrastructure.Middlewares
+{
+    public static class FailingMiddlewareAppBuilderExtensions
+    {
+        public static IApplicationBuilder UseFailingMiddleware(this IApplicationBuilder builder)
+        {
+            return UseFailingMiddleware(builder, null);
+        }
+        public static IApplicationBuilder UseFailingMiddleware(this IApplicationBuilder builder, Action<FailingOptions> action)
+        {
+            var options = new FailingOptions();
+            action?.Invoke(options);
+            builder.UseMiddleware<FailingMiddleware>(options);
+            return builder;
+        }
+    }
+}

src/Services/Ordering/Ordering.API/Infrastructure/Middlewares/FailingOptions.cs

@@ -0,0 +1,12 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace Ordering.API.Infrastructure.Middlewares
+{
+    public class FailingOptions
+    {
+        public string ConfigPath = "/Failing";
+    }
+}

src/Services/Ordering/Ordering.API/Startup.cs

@@ -3,6 +3,7 @@
     using AspNetCore.Http;
     using Autofac;
     using Autofac.Extensions.DependencyInjection;
+    using global::Ordering.API.Infrastructure.Middlewares;
     using Infrastructure;
     using Infrastructure.Auth;
     using Infrastructure.AutofacModules;
@@ -109,6 +110,8 @@ public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerF
 
             app.UseCors("CorsPolicy");
 
+            app.UseFailingMiddleware();
+
             ConfigureAuth(app);
 
             app.UseMvcWithDefaultRoute();