From f65b650805da166ae02a5ccbc925a638abf6f682 Mon Sep 17 00:00:00 2001
From: Cijo Thomas <cithomas@microsoft.com>
Date: Mon, 19 Apr 2021 22:31:28 -0700
Subject: [PATCH] AspNetCore instrumentation options to be configurable from DI
 (#1997)

---
 examples/AspNetCore/Startup.cs                | 14 +++++++++++
 examples/AspNetCore/appsettings.json          |  3 +++
 .../CHANGELOG.md                              |  4 ++++
 ...elemetry.Instrumentation.AspNetCore.csproj |  1 +
 .../README.md                                 | 23 +++++++++++++++++++
 .../TracerProviderBuilderExtensions.cs        | 21 +++++++++++++----
 .../Internal/ServiceProviderExtensions.cs     |  5 ++--
 7 files changed, 64 insertions(+), 7 deletions(-)

diff --git a/examples/AspNetCore/Startup.cs b/examples/AspNetCore/Startup.cs
index c2c4a4a817e..625c7c16615 100644
--- a/examples/AspNetCore/Startup.cs
+++ b/examples/AspNetCore/Startup.cs
@@ -24,6 +24,7 @@
 using Microsoft.Extensions.Hosting;
 using Microsoft.OpenApi.Models;
 using OpenTelemetry.Exporter;
+using OpenTelemetry.Instrumentation.AspNetCore;
 using OpenTelemetry.Resources;
 using OpenTelemetry.Trace;
 
@@ -95,6 +96,19 @@ public void ConfigureServices(IServiceCollection services)
                         .AddAspNetCoreInstrumentation()
                         .AddHttpClientInstrumentation()
                         .AddConsoleExporter());
+
+                    // For options which can be bound from IConfiguration.
+                    services.Configure<AspNetCoreInstrumentationOptions>(this.Configuration.GetSection("AspNetCoreInstrumentation"));
+
+                    // For options which can be configured from code only.
+                    services.Configure<AspNetCoreInstrumentationOptions>(options =>
+                    {
+                        options.Filter = (req) =>
+                        {
+                            return req.Request.Host != null;
+                        };
+                    });
+
                     break;
             }
         }
diff --git a/examples/AspNetCore/appsettings.json b/examples/AspNetCore/appsettings.json
index 3279eec3559..d9e5cf957cc 100644
--- a/examples/AspNetCore/appsettings.json
+++ b/examples/AspNetCore/appsettings.json
@@ -20,5 +20,8 @@
   "Otlp": {
     "ServiceName": "otlp-test",
     "Endpoint": "http://localhost:4317"
+  },
+  "AspNetCoreInstrumentation": {
+    "RecordException": "true"
   }
 }
diff --git a/src/OpenTelemetry.Instrumentation.AspNetCore/CHANGELOG.md b/src/OpenTelemetry.Instrumentation.AspNetCore/CHANGELOG.md
index 1eb669d13e3..46cf43e7411 100644
--- a/src/OpenTelemetry.Instrumentation.AspNetCore/CHANGELOG.md
+++ b/src/OpenTelemetry.Instrumentation.AspNetCore/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+* When using OpenTelemetry.Extensions.Hosting you can now bind
+  `AspNetCoreInstrumentationOptions` from DI.
+  ([#1997](https://github.com/open-telemetry/opentelemetry-dotnet/pull/1997))
+
 ## 1.0.0-rc3
 
 Released 2021-Mar-19
diff --git a/src/OpenTelemetry.Instrumentation.AspNetCore/OpenTelemetry.Instrumentation.AspNetCore.csproj b/src/OpenTelemetry.Instrumentation.AspNetCore/OpenTelemetry.Instrumentation.AspNetCore.csproj
index ccc20812aab..2f127aa0863 100644
--- a/src/OpenTelemetry.Instrumentation.AspNetCore/OpenTelemetry.Instrumentation.AspNetCore.csproj
+++ b/src/OpenTelemetry.Instrumentation.AspNetCore/OpenTelemetry.Instrumentation.AspNetCore.csproj
@@ -9,6 +9,7 @@
   <ItemGroup>
     <Compile Include="$(RepoRoot)\src\OpenTelemetry.Instrumentation.GrpcNetClient\GrpcTagHelper.cs" Link="Includes\GrpcTagHelper.cs" />
     <Compile Include="$(RepoRoot)\src\OpenTelemetry.Instrumentation.GrpcNetClient\StatusCanonicalCode.cs" Link="Includes\StatusCanonicalCode.cs" />
+    <Compile Include="$(RepoRoot)\src\OpenTelemetry\Internal\ServiceProviderExtensions.cs" Link="Includes\ServiceProviderExtensions.cs" />
   </ItemGroup>
 
   <ItemGroup>
diff --git a/src/OpenTelemetry.Instrumentation.AspNetCore/README.md b/src/OpenTelemetry.Instrumentation.AspNetCore/README.md
index 0a078229bec..60a70cce8d6 100644
--- a/src/OpenTelemetry.Instrumentation.AspNetCore/README.md
+++ b/src/OpenTelemetry.Instrumentation.AspNetCore/README.md
@@ -57,6 +57,29 @@ This instrumentation can be configured to change the default behavior by using
 `AspNetCoreInstrumentationOptions`, which allows adding [`Filter`](#filter),
 [`Enrich`](#enrich) as explained below.
 
+// TODO: This section could be refined.
+When used with [`OpenTelemetry.Extensions.Hosting`](../OpenTelemetry.Extensions.Hosting/README.md),
+all configurations to `AspNetCoreInstrumentationOptions` can be done in the `ConfigureServices`
+method of you applications `Startup` class as shown below.
+
+```csharp
+// Configure
+services.Configure<AspNetCoreInstrumentationOptions>(options =>
+        {
+            options.Filter = (req) =>
+            {
+                // only collect telemetry about HTTP GET requests
+                return httpContext.Request.Method.Equals("GET");
+            };
+        });
+
+services.AddOpenTelemetryTracing(
+        (builder) => builder
+            .AddAspNetCoreInstrumentation()
+            .AddJaegerExporter()
+            );
+```
+
 ### Filter
 
 This instrumentation by default collects all the incoming http requests. It
diff --git a/src/OpenTelemetry.Instrumentation.AspNetCore/TracerProviderBuilderExtensions.cs b/src/OpenTelemetry.Instrumentation.AspNetCore/TracerProviderBuilderExtensions.cs
index 6ae19062faa..faba8be5714 100644
--- a/src/OpenTelemetry.Instrumentation.AspNetCore/TracerProviderBuilderExtensions.cs
+++ b/src/OpenTelemetry.Instrumentation.AspNetCore/TracerProviderBuilderExtensions.cs
@@ -40,14 +40,25 @@ public static TracerProviderBuilder AddAspNetCoreInstrumentation(
                 throw new ArgumentNullException(nameof(builder));
             }
 
-            var aspnetCoreOptions = new AspNetCoreInstrumentationOptions();
-            configureAspNetCoreInstrumentationOptions?.Invoke(aspnetCoreOptions);
-            builder.AddInstrumentation(() => new AspNetCoreInstrumentation(aspnetCoreOptions));
+            if (builder is IDeferredTracerProviderBuilder deferredTracerProviderBuilder)
+            {
+                return deferredTracerProviderBuilder.Configure((sp, builder) =>
+                {
+                    AddAspNetCoreInstrumentation(builder, sp.GetOptions<AspNetCoreInstrumentationOptions>(), configureAspNetCoreInstrumentationOptions);
+                });
+            }
+
+            return AddAspNetCoreInstrumentation(builder, new AspNetCoreInstrumentationOptions(), configureAspNetCoreInstrumentationOptions);
+        }
+
+        private static TracerProviderBuilder AddAspNetCoreInstrumentation(TracerProviderBuilder builder, AspNetCoreInstrumentationOptions options, Action<AspNetCoreInstrumentationOptions> configure = null)
+        {
+            configure?.Invoke(options);
+            var instrumentation = new AspNetCoreInstrumentation(options);
             builder.AddSource(HttpInListener.ActivitySourceName);
             builder.AddLegacySource(HttpInListener.ActivityOperationName); // for the activities created by AspNetCore
             builder.AddLegacySource(HttpInListener.ActivityNameByHttpInListener); // for the sibling activities created by the instrumentation library
-
-            return builder;
+            return builder.AddInstrumentation(() => instrumentation);
         }
     }
 }
diff --git a/src/OpenTelemetry/Internal/ServiceProviderExtensions.cs b/src/OpenTelemetry/Internal/ServiceProviderExtensions.cs
index d6c53d4ae66..ff899cc3fe8 100644
--- a/src/OpenTelemetry/Internal/ServiceProviderExtensions.cs
+++ b/src/OpenTelemetry/Internal/ServiceProviderExtensions.cs
@@ -14,7 +14,8 @@
 // limitations under the License.
 // </copyright>
 
-#if NET461 || NETSTANDARD2_0
+#if NET461 || NETSTANDARD2_0 || NETSTANDARD2_1
+using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Options;
 #endif
 
@@ -34,7 +35,7 @@ internal static class ServiceProviderExtensions
         public static T GetOptions<T>(this IServiceProvider serviceProvider)
             where T : class, new()
         {
-#if NET461 || NETSTANDARD2_0
+#if NET461 || NETSTANDARD2_0 || NETSTANDARD2_1
             IOptions<T> options = (IOptions<T>)serviceProvider.GetService(typeof(IOptions<T>));
 
             // Note: options could be null if user never invoked services.AddOptions().