Add example for chaos engineering

samples/Chaos/Chaos.csproj

@@ -0,0 +1,15 @@
+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <RootNamespace>Chaos</RootNamespace>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Extensions.Http.Resilience" />
+    <PackageReference Include="Polly.Core" />
+  </ItemGroup>
+
+</Project>

samples/Chaos/ChaosManager.cs

@@ -0,0 +1,45 @@
+using Polly;
+
+namespace Chaos;
+
+internal class ChaosManager(IWebHostEnvironment environment, IHttpContextAccessor contextAccessor) : IChaosManager
+{
+    private const string UserQueryParam = "user";
+
+    private const string TestUser = "test";
+
+    public ValueTask<bool> IsChaosEnabledAsync(ResilienceContext context)
+    {
+        if (environment.IsDevelopment())
+        {
+            return ValueTask.FromResult(true);
+        }
+
+        // This condition is demonstrative and not recommended to use in real apps.
+        if (environment.IsProduction() &&
+            contextAccessor.HttpContext is { } httpContext &&
+            httpContext.Request.Query.TryGetValue(UserQueryParam, out var values) &&
+            values == TestUser)
+        {
+            // Enable chaos for 'test' user even in production 
+            return ValueTask.FromResult(true);
+        }
+
+        return ValueTask.FromResult(false);
+    }
+
+    public ValueTask<double> GetInjectionRateAsync(ResilienceContext context)
+    {
+        if (environment.IsDevelopment())
+        {
+            return ValueTask.FromResult(0.05);
+        }
+
+        if (environment.IsProduction())
+        {
+            return ValueTask.FromResult(0.03);
+        }
+
+        return ValueTask.FromResult(0.0);
+    }
+}

samples/Chaos/IChaosManager.cs

@@ -0,0 +1,13 @@
+using Polly;
+
+namespace Chaos;
+
+/// <summary>
+/// Abstraction for controlling chaos injection.
+/// </summary>
+public interface IChaosManager
+{
+    ValueTask<bool> IsChaosEnabledAsync(ResilienceContext context);
+
+    ValueTask<double> GetInjectionRateAsync(ResilienceContext context);
+}

samples/Chaos/Program.cs

@@ -0,0 +1,77 @@
+using Chaos;
+using Microsoft.Extensions.DependencyInjection.Extensions;
+using Microsoft.Extensions.Http.Resilience;
+using Polly;
+using Polly.Simmy;
+using Polly.Simmy.Fault;
+using Polly.Simmy.Latency;
+using Polly.Simmy.Outcomes;
+
+var builder = WebApplication.CreateBuilder(args);
+var services = builder.Services;
+
+services.TryAddSingleton<IChaosManager, ChaosManager>();
+services.AddHttpContextAccessor();
+
+var httpClientBuilder = services.AddHttpClient<TodosClient>(client => client.BaseAddress = new Uri("https://jsonplaceholder.typicode.com"));
+
+// Configure the standard resilience handler
+httpClientBuilder
+    .AddStandardResilienceHandler()
+    .Configure(options => 
+    {
+        // Update attempt timeout to 1 second
+        options.AttemptTimeout.Timeout = TimeSpan.FromSeconds(1);
+
+        // Update circuit breaker to handle transient errors and InvalidOperationException
+        options.CircuitBreaker.ShouldHandle = args => args.Outcome switch
+        {
+            {} outcome when HttpClientResiliencePredicates.IsTransient(outcome) => PredicateResult.True(),
+            { Exception: InvalidOperationException } => PredicateResult.True(),
+            _ => PredicateResult.False()
+        };
+
+        // Update retry strategy to handle transient errors and InvalidOperationException
+        options.Retry.ShouldHandle = args => args.Outcome switch
+        {
+            {} outcome when HttpClientResiliencePredicates.IsTransient(outcome) => PredicateResult.True(),
+            { Exception: InvalidOperationException } => PredicateResult.True(),
+            _ => PredicateResult.False()
+        };
+    });
+
+// Configure the chaos injection
+httpClientBuilder.AddResilienceHandler("chaos", (builder, context) =>
+{
+    // Get IChaosManager from dependency injection
+    var chaosManager = context.ServiceProvider.GetRequiredService<IChaosManager>();
+
+    builder
+        .AddChaosLatency(new ChaosLatencyStrategyOptions
+        {
+            EnabledGenerator = args => chaosManager.IsChaosEnabledAsync(args.Context),
+            InjectionRateGenerator = args => chaosManager.GetInjectionRateAsync(args.Context),
+            Latency = TimeSpan.FromSeconds(5)
+        })
+        .AddChaosFault(new ChaosFaultStrategyOptions
+        {
+            EnabledGenerator = args => chaosManager.IsChaosEnabledAsync(args.Context),
+            InjectionRateGenerator = args => chaosManager.GetInjectionRateAsync(args.Context),
+            FaultGenerator = new FaultGenerator().AddException(() => new InvalidOperationException("Chaos strategy injection!"))
+        })
+        .AddChaosOutcome(new ChaosOutcomeStrategyOptions<HttpResponseMessage>
+        {
+            EnabledGenerator = args => chaosManager.IsChaosEnabledAsync(args.Context),
+            InjectionRateGenerator = args => chaosManager.GetInjectionRateAsync(args.Context),
+            OutcomeGenerator = new OutcomeGenerator<HttpResponseMessage>().AddResult(() => new HttpResponseMessage(System.Net.HttpStatusCode.InternalServerError))
+        });
+});
+
+// Run the app
+var app = builder.Build();
+app.MapGet("/", async (TodosClient client, HttpContext httpContext, CancellationToken cancellationToken) =>
+{
+    return await client.GetTodosAsync(cancellationToken);
+});
+
+app.Run();

samples/Chaos/Properties/launchSettings.json

@@ -0,0 +1,12 @@
+{
+  "profiles": {
+    "Chaos": {
+      "commandName": "Project",
+      "launchBrowser": true,
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development"
+      },
+      "applicationUrl": "https://localhost:62683;http://localhost:62684"
+    }
+  }
+}

samples/Chaos/README.md

@@ -0,0 +1,10 @@
+# Chaos Example
+
+This example demonstrates how to use new [chaos engineering](https://www.pollydocs.org/chaos) tools in Polly to inject chaos into HTTP client communication.
+The HTTP client communicates with the `https://jsonplaceholder.typicode.com/todos` endpoint.
+
+To test the application:
+
+- Run the app using the `dotnet run` command.
+- Access the root endpoint `https://localhost:62683` and refresh it multiple times.
+- Observe the logs in out console window. You should see chaos injection and also mitigation of chaos by resilience strategies.

samples/Chaos/TodoModel.cs

@@ -0,0 +1,7 @@
+using System.Text.Json.Serialization;
+
+namespace Chaos;
+
+public record TodoModel(
+    [property: JsonPropertyName("id")] int Id,
+    [property: JsonPropertyName("title")] string Title);

samples/Chaos/TodosClient.cs

@@ -0,0 +1,7 @@
+namespace Chaos;
+
+public class TodosClient(HttpClient client)
+{
+    public async Task<IEnumerable<TodoModel>> GetTodosAsync(CancellationToken cancellationToken)
+        => await client.GetFromJsonAsync<IEnumerable<TodoModel>>("/todos", cancellationToken) ?? [];
+}

samples/Chaos/appsettings.Development.json

@@ -0,0 +1,8 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  }
+}

samples/Chaos/appsettings.json

@@ -0,0 +1,9 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  },
+  "AllowedHosts": "*"
+}

samples/README.md

@@ -7,5 +7,6 @@ This repository contains a solution with basic examples demonstrating the creati
 - [`Retries`](./Retries) - This part explains how to configure a retry resilience strategy.
 - [`Extensibility`](./Extensibility) - In this part, you can learn how Polly can be extended with custom resilience strategies.
 - [`DependencyInjection`](./DependencyInjection) - This section demonstrates the integration of Polly with `IServiceCollection`.
+- [`Chaos`](./Chaos) - Simple web application that communicates with an external service using HTTP client. It uses chaos strategies to inject chaos into HTTP client calls.
 
 These examples are designed as a quick-start guide to Polly. If you wish to explore more advanced scenarios and further enhance your learning, consider visiting the [Polly-Samples](https://github.com/App-vNext/Polly-Samples) repository.

samples/Samples.sln

@@ -8,6 +8,7 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution
 		.editorconfig = .editorconfig
 		Directory.Build.props = Directory.Build.props
 		Directory.Build.targets = Directory.Build.targets
+		..\Directory.Packages.props = ..\Directory.Packages.props
 		README.md = README.md
 	EndProjectSection
 EndProject
@@ -21,6 +22,8 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Retries", "Retries\Retries.
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "DependencyInjection", "DependencyInjection\DependencyInjection.csproj", "{9B8BFE03-4457-4C55-91AD-4096DDE622C3}"
 EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Chaos", "Chaos\Chaos.csproj", "{A296E17C-B95F-4B15-8B0D-9D6CC0929A1D}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -47,6 +50,10 @@ Global
 		{9B8BFE03-4457-4C55-91AD-4096DDE622C3}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{9B8BFE03-4457-4C55-91AD-4096DDE622C3}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{9B8BFE03-4457-4C55-91AD-4096DDE622C3}.Release|Any CPU.Build.0 = Release|Any CPU
+		{A296E17C-B95F-4B15-8B0D-9D6CC0929A1D}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{A296E17C-B95F-4B15-8B0D-9D6CC0929A1D}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{A296E17C-B95F-4B15-8B0D-9D6CC0929A1D}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{A296E17C-B95F-4B15-8B0D-9D6CC0929A1D}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE