feat: restructure and support custom sampling

Asos.OpenTelemetry/Asos.OpenTelemetry.AspNetCore.Tests/Asos.OpenTelemetry.AspNetCore.Tests.csproj

@@ -0,0 +1,29 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>net8.0</TargetFramework>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+
+        <IsPackable>false</IsPackable>
+        <IsTestProject>true</IsTestProject>
+    </PropertyGroup>
+
+    <ItemGroup>
+        <PackageReference Include="coverlet.collector" Version="6.0.0"/>
+        <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0"/>
+        <PackageReference Include="NSubstitute" Version="5.3.0" />
+        <PackageReference Include="NUnit" Version="3.14.0"/>
+        <PackageReference Include="NUnit.Analyzers" Version="3.9.0"/>
+        <PackageReference Include="NUnit3TestAdapter" Version="4.5.0"/>
+    </ItemGroup>
+
+    <ItemGroup>
+        <Using Include="NUnit.Framework"/>
+    </ItemGroup>
+
+    <ItemGroup>
+      <ProjectReference Include="..\Asos.OpenTelemetry.AspNetCore\Asos.OpenTelemetry.AspNetCore.csproj" />
+    </ItemGroup>
+
+</Project>

Asos.OpenTelemetry/Asos.OpenTelemetry.AspNetCore.Tests/ConfigurableRouteSamplerTests.cs

@@ -0,0 +1,161 @@
+using System.Text.RegularExpressions;
+using Asos.OpenTelemetry.AspNetCore.Sampling;
+using Microsoft.AspNetCore.Http;
+using NSubstitute;
+using OpenTelemetry.Trace;
+
+namespace Asos.OpenTelemetry.AspNetCore.Tests;
+
+[TestFixture]
+public class ConfigurableRouteSamplerTests
+{
+    private IHttpContextAccessor _httpContextAccessor;
+    private RouteSamplingOptions _options;
+
+    [SetUp]
+    public void Setup()
+    {
+        _httpContextAccessor = Substitute.For<IHttpContextAccessor>();
+        _options = new RouteSamplingOptions
+        {
+            DefaultRate = 0.5,
+            SamplingRules =
+            [
+                new SamplingRule
+                {
+                    RoutePattern = "^/api/test$",
+                    Method = "GET",
+                    Rate = 1.0,
+                    CompiledPattern = new Regex("^/api/test$", RegexOptions.IgnoreCase | RegexOptions.Compiled)
+                }
+            ]
+        };
+    }
+
+    [Test]
+    public void ShouldSample_DefaultSamplingRate_WhenNoMatchingRouteOrMethod()
+    {
+        var httpContext = new DefaultHttpContext
+        {
+            Request = { Path = "/unknown", Method = "POST" }
+        };
+        _httpContextAccessor.HttpContext.Returns(httpContext);
+
+        var sampler = new ConfigurableRouteSampler(_options, _httpContextAccessor);
+        var result = sampler.ShouldSample(default);
+
+        Assert.That(result.Decision, Is.EqualTo(SamplingDecision.Drop).Or.EqualTo(SamplingDecision.RecordAndSample));
+    }
+
+    [Test]
+    public void ShouldSample_SpecificRouteAndMethodMatch()
+    {
+        var httpContext = new DefaultHttpContext
+        {
+            Request = { Path = "/api/test", Method = "GET" }
+        };
+        _httpContextAccessor.HttpContext.Returns(httpContext);
+
+        var sampler = new ConfigurableRouteSampler(_options, _httpContextAccessor);
+        var result = sampler.ShouldSample(default);
+
+        Assert.That(result.Decision, Is.EqualTo(SamplingDecision.RecordAndSample));
+    }
+
+    [Test]
+    public void ShouldSample_BoundarySamplingRates()
+    {
+        _options.DefaultRate = 0.0;
+        var sampler = new ConfigurableRouteSampler(_options, _httpContextAccessor);
+        var result = sampler.ShouldSample(default);
+
+        Assert.That(result.Decision, Is.EqualTo(SamplingDecision.Drop));
+
+        _options.DefaultRate = 1.0;
+        sampler = new ConfigurableRouteSampler(_options, _httpContextAccessor);
+        result = sampler.ShouldSample(default);
+
+        Assert.That(result.Decision, Is.EqualTo(SamplingDecision.RecordAndSample));
+    }
+
+    [Test]
+    public void ShouldSample_NullHttpContext()
+    {
+        _httpContextAccessor.HttpContext.Returns((HttpContext)null!);
+
+        var sampler = new ConfigurableRouteSampler(_options, _httpContextAccessor);
+        var result = sampler.ShouldSample(default);
+
+        Assert.That(result.Decision, Is.EqualTo(SamplingDecision.Drop).Or.EqualTo(SamplingDecision.RecordAndSample));
+    }
+
+    [Test]
+    public void ShouldSample_CaseInsensitiveMethodMatching()
+    {
+        var httpContext = new DefaultHttpContext
+        {
+            Request = { Path = "/api/test", Method = "get" }
+        };
+        _httpContextAccessor.HttpContext.Returns(httpContext);
+
+        var sampler = new ConfigurableRouteSampler(_options, _httpContextAccessor);
+        var result = sampler.ShouldSample(default);
+
+        Assert.That(result.Decision, Is.EqualTo(SamplingDecision.RecordAndSample));
+    }
+
+    [Test]
+    public void ShouldSample_RoutePatternMatching()
+    {
+        var httpContext = new DefaultHttpContext
+        {
+            Request = { Path = "/api/test", Method = "GET" }
+        };
+        _httpContextAccessor.HttpContext.Returns(httpContext);
+
+        var sampler = new ConfigurableRouteSampler(_options, _httpContextAccessor);
+        var result = sampler.ShouldSample(default);
+
+        Assert.That(result.Decision, Is.EqualTo(SamplingDecision.RecordAndSample));
+    }
+
+    [Test]
+    public void ShouldSample_EmptySamplingRules()
+    {
+        _options.SamplingRules.Clear();
+
+        var httpContext = new DefaultHttpContext
+        {
+            Request = { Path = "/api/test", Method = "GET" }
+        };
+        _httpContextAccessor.HttpContext.Returns(httpContext);
+
+        var sampler = new ConfigurableRouteSampler(_options, _httpContextAccessor);
+        var result = sampler.ShouldSample(default);
+
+        Assert.That(result.Decision, Is.EqualTo(SamplingDecision.Drop).Or.EqualTo(SamplingDecision.RecordAndSample));
+    }
+
+    [Test]
+    public void ShouldSample_InvalidSamplingRate()
+    {
+        _options.DefaultRate = -1.0;
+
+        var sampler = new ConfigurableRouteSampler(_options, _httpContextAccessor);
+        var result = sampler.ShouldSample(default);
+
+        Assert.That(result.Decision, Is.EqualTo(SamplingDecision.Drop));
+    }
+
+    [Test]
+    public void ShouldSample_Concurrency()
+    {
+        var sampler = new ConfigurableRouteSampler(_options, _httpContextAccessor);
+
+        Parallel.For(0, 100, _ =>
+        {
+            var result = sampler.ShouldSample(default);
+            Assert.That(result.Decision, Is.EqualTo(SamplingDecision.Drop).Or.EqualTo(SamplingDecision.RecordAndSample));
+        });
+    }
+}

Asos.OpenTelemetry/Asos.OpenTelemetry.AspNetCore.Tests/OpenTelemetrySetupTests.cs

@@ -0,0 +1,46 @@
+using System.Text.RegularExpressions;
+using Asos.OpenTelemetry.AspNetCore.Sampling;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Options;
+using OpenTelemetry.Trace;
+
+namespace Asos.OpenTelemetry.AspNetCore.Tests;
+
+public class OpenTelemetrySetupTests
+{
+    [Test]
+    public void ConfigureOpenTelemetry_RegistersRequiredServices()
+    {
+        var builder = WebApplication.CreateBuilder();
+        builder.Configuration["OpenTelemetry:Sampling:SamplingRules:0:RoutePattern"] = "/api/test";
+
+        builder.Services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();
+
+        builder.ConfigureOpenTelemetryCustomSampling(options =>
+        {
+            options.SamplingRatio = 0.5f;
+            options.ConnectionString = "InstrumentationKey=12345-12345-12345-12345";
+        });
+
+        var provider = builder.Services.BuildServiceProvider();
+
+        var tracerProvider = provider.GetRequiredService<TracerProvider>();
+        Assert.That(tracerProvider, Is.Not.Null);
+
+        // Assert RouteSamplingOptions are bound correctly
+        var routeSamplingOptions = provider.GetRequiredService<IOptions<RouteSamplingOptions>>().Value;
+        Assert.That(routeSamplingOptions.SamplingRules, Has.Exactly(1).Items);
+        Assert.Multiple(() =>
+        {
+            Assert.That(routeSamplingOptions.SamplingRules[0].RoutePattern, Is.EqualTo("/api/test"));
+            Assert.That(routeSamplingOptions.SamplingRules[0].CompiledPattern, Is.Not.Null);
+        });
+        Assert.That(routeSamplingOptions.SamplingRules[0].CompiledPattern, Is.InstanceOf<Regex>());
+
+        // Assert that ConfigurableRouteSampler is registered
+        var sampler = provider.GetService<ConfigurableRouteSampler>();
+        Assert.That(sampler, Is.Not.Null);
+    }
+}

Asos.OpenTelemetry/Asos.OpenTelemetry.AspNetCore/Asos.OpenTelemetry.AspNetCore.csproj

@@ -0,0 +1,26 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+        <PackageOutputPath>./nupkg</PackageOutputPath>        
+        <PackageRequireLicenseAcceptance>false</PackageRequireLicenseAcceptance>
+        <Authors>asos</Authors>
+        <Product>Asos.OpenTelemetry.AspNetCore</Product>
+        <PackageId>Asos.OpenTelemetry.AspNetCore</PackageId>
+        <Description>OpenTelemetry functionality and extensions for use in AspNetCore applications</Description>
+        <TargetFramework>net8.0</TargetFramework>
+        <PackageIcon>otel_icon.png</PackageIcon>
+        <PackageIconUrl />        
+        <PackageLicenseExpression>MIT</PackageLicenseExpression>
+        <PackageReadmeFile>README.md</PackageReadmeFile>
+        <GenerateDocumentationFile>true</GenerateDocumentationFile>
+    </PropertyGroup>
+    <ItemGroup>
+        <None Include="README.md" Pack="true" PackagePath="." />
+        <None Include="otel_icon.png" Pack="true" PackagePath="." />
+    </ItemGroup>    
+    <ItemGroup>
+      <PackageReference Include="Azure.Monitor.OpenTelemetry.AspNetCore" Version="1.2.0" />
+    </ItemGroup>
+</Project>

Asos.OpenTelemetry/Asos.OpenTelemetry.AspNetCore/README.md

@@ -0,0 +1,69 @@
+# Open Telemetry extensions for Asp Net Core
+
+A library for configuring OpenTelemetry in ASP.NET Core applications,
+
+## What's it for?
+
+This library is intended to help modify the default behaviour of OpenTelemetry in ASP.NET Core applications, allowing
+some customisation of the way data is exported, sampled and other behaviours.
+
+## How does it work?
+
+Extension methods are available that allow you to change the behaviour of OpenTelemetry via the WebApplicationBuilder
+
+```csharp
+builder.ConfigureOpenTelemetryCustomSampling(
+    options =>
+    {
+        // whatever options you want to set
+    });
+```
+
+The `ConfigureOpenTelemetryCustomSampling` method allows you to set up custom sampling rules, which can be used to control
+the sampling rate of different routes or HTTP methods in your application.
+
+To define the rules, create a section in your `appsettings.json` file under the `OpenTelemetry:Sampling` path.
+
+```json
+{
+  "OpenTelemetry": {
+    "Sampling": {
+      "DefaultRate": 0.05,
+      "SamplingRules": [
+        {
+          "RoutePattern": "^/api/customers/\\d+$",
+          "Method": "GET",
+          "Rate": 1.0
+        },
+        {
+          "RoutePattern": "^/api/orders$",
+          "Method": "POST",
+          "Rate": 0.25
+        },
+        {
+          "RoutePattern": "^/health$",
+          "Method": "GET",
+          "Rate": 0.0
+        }
+      ]
+    }
+  }
+}
+```
+
+By doing so, you can control the sampling rate for specific routes and HTTP methods in your ASP.NET Core application.
+
+Be aware that different sampling rates can break the consistency of your traces, so use this feature with caution. It's a good
+option when you don't call into external APIs and just call your own dependencies, as it can help reduce the amount of data
+you produce
+
+For example, if you have a GET endpoint that only calls a database and no other services, is successful a very high percentage of 
+time and you don't need to see every single request, you can set the sampling rate to 0.05 (5%) for that endpoint.
+
+You might have another endpoint that performs a POST operation and calls into an external API, which is less reliable and you want to see
+every request, so you can set the sampling rate to 1.0 (100%) for that endpoint.
+
+
+
+
+