Add simulated latency middleware

A new middleware, SimulatedLatencyMiddleware, has been added to simulate latency in a designated range. This can be used for testing purposes by delaying a request for a random amount of time. Additionally, an extension method for IApplicationBuilder has been implemented to conveniently add this functionality to the application's pipeline.

src/bundles/Elsa.Server.Web/Middleware/SimulatedLatencyMiddleware.cs

@@ -0,0 +1,56 @@
+using JetBrains.Annotations;
+
+namespace Elsa.Server.Web.Middleware;
+
+/// <summary>
+/// Simulates latency by delaying the request for a random amount of time between the specified minimum and maximum durations.
+/// </summary>
+/// <param name="next"></param>
+/// <param name="min"></param>
+/// <param name="max"></param>
+[UsedImplicitly]
+public class SimulatedLatencyMiddleware(
+    RequestDelegate next,
+    TimeSpan min,
+    TimeSpan max)
+{
+    private readonly int _minDelayInMs = (int)min.TotalMilliseconds;
+    private readonly int _maxDelayInMs = (int)max.TotalMilliseconds;
+    private readonly ThreadLocal<Random> _random = new(() => new Random());
+
+    /// <summary>
+    /// Invokes the middleware.
+    /// </summary>
+    /// <param name="context"></param>
+    [UsedImplicitly]
+    public async Task Invoke(HttpContext context)
+    {
+        int delayInMs = _random.Value!.Next(
+            _minDelayInMs,
+            _maxDelayInMs
+        );
+
+        await Task.Delay(delayInMs);
+        await next(context);
+    }
+}
+
+/// <summary>
+/// Provides extension methods for the <see cref="IApplicationBuilder"/> interface.
+/// </summary>
+public static class AppBuilderExtensions
+{
+    /// <summary>
+    /// Adds the <see cref="SimulatedLatencyMiddleware"/> to the application's request pipeline.
+    /// </summary>
+    /// <param name="app"></param>
+    /// <param name="min"></param>
+    /// <param name="max"></param>
+    public static IApplicationBuilder UseSimulatedLatency(
+        this IApplicationBuilder app,
+        TimeSpan min,
+        TimeSpan max)
+    {
+        return app.UseMiddleware<SimulatedLatencyMiddleware>(min, max);
+    }
+}

src/bundles/Elsa.Server.Web/Program.cs

@@ -16,6 +16,7 @@ using Elsa.MongoDb.Modules.Identity;
 using Elsa.MongoDb.Modules.Management;
 using Elsa.MongoDb.Modules.Runtime;
 using Elsa.Server.Web;
+using Elsa.Server.Web.Middleware;
 using Elsa.Workflows.Management.Compression;
 using Microsoft.Data.Sqlite;
 using Microsoft.Extensions.Options;
@@ -249,6 +250,11 @@ services.AddCors(cors => cors.AddDefaultPolicy(policy => policy.AllowAnyHeader()
 // Build the web application.
 var app = builder.Build();
 
+// app.UseSimulatedLatency(
+//     TimeSpan.FromMilliseconds(1000),
+//     TimeSpan.FromMilliseconds(3000)
+// );
+
 // Configure the pipeline.
 if (app.Environment.IsDevelopment())
     app.UseDeveloperExceptionPage();