[di] Expose a detached MeterProviderBuilder extension on IServiceCollection which may modify services

src/OpenTelemetry.Api.ProviderBuilderExtensions/.publicApi/net462/PublicAPI.Unshipped.txt

@@ -1 +1,2 @@
+static OpenTelemetry.Metrics.OpenTelemetryDependencyInjectionMetricsServiceCollectionExtensions.ConfigureOpenTelemetryMeterProvider(this Microsoft.Extensions.DependencyInjection.IServiceCollection! services, System.Action<OpenTelemetry.Metrics.MeterProviderBuilder!>! configure) -> Microsoft.Extensions.DependencyInjection.IServiceCollection!
 static OpenTelemetry.Trace.OpenTelemetryDependencyInjectionTracingServiceCollectionExtensions.ConfigureOpenTelemetryTracerProvider(this Microsoft.Extensions.DependencyInjection.IServiceCollection! services, System.Action<OpenTelemetry.Trace.TracerProviderBuilder!>! configure) -> Microsoft.Extensions.DependencyInjection.IServiceCollection!

src/OpenTelemetry.Api.ProviderBuilderExtensions/.publicApi/netstandard2.0/PublicAPI.Unshipped.txt

@@ -1 +1,2 @@
+static OpenTelemetry.Metrics.OpenTelemetryDependencyInjectionMetricsServiceCollectionExtensions.ConfigureOpenTelemetryMeterProvider(this Microsoft.Extensions.DependencyInjection.IServiceCollection! services, System.Action<OpenTelemetry.Metrics.MeterProviderBuilder!>! configure) -> Microsoft.Extensions.DependencyInjection.IServiceCollection!
 static OpenTelemetry.Trace.OpenTelemetryDependencyInjectionTracingServiceCollectionExtensions.ConfigureOpenTelemetryTracerProvider(this Microsoft.Extensions.DependencyInjection.IServiceCollection! services, System.Action<OpenTelemetry.Trace.TracerProviderBuilder!>! configure) -> Microsoft.Extensions.DependencyInjection.IServiceCollection!

src/OpenTelemetry.Api.ProviderBuilderExtensions/CHANGELOG.md

@@ -14,6 +14,12 @@
   created).
   ([#4508](https://github.com/open-telemetry/opentelemetry-dotnet/pull/4508))
 
+* Added an `IServiceCollection.ConfigureOpenTelemetryMeterProvider` overload
+  which may be used to configure `MeterProviderBuilder`s while the
+  `IServiceCollection` is modifiable (before the `IServiceProvider` has been
+  created).
+  ([#4517](https://github.com/open-telemetry/opentelemetry-dotnet/pull/4517))
+
 ## 1.5.0-alpha.2
 
 Released 2023-Mar-31

src/OpenTelemetry.Api.ProviderBuilderExtensions/Metrics/MeterProviderServiceCollectionBuilder.cs

@@ -0,0 +1,94 @@
+// <copyright file="MeterProviderServiceCollectionBuilder.cs" company="OpenTelemetry Authors">
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// </copyright>
+
+using Microsoft.Extensions.DependencyInjection;
+using OpenTelemetry.Internal;
+
+namespace OpenTelemetry.Metrics;
+
+internal sealed class MeterProviderServiceCollectionBuilder : MeterProviderBuilder, IMeterProviderBuilder
+{
+    public MeterProviderServiceCollectionBuilder(IServiceCollection services)
+    {
+        services.ConfigureOpenTelemetryMeterProvider((sp, builder) => this.Services = null);
+
+        this.Services = services;
+    }
+
+    public IServiceCollection? Services { get; set; }
+
+    public MeterProvider? Provider => null;
+
+    /// <inheritdoc />
+    public override MeterProviderBuilder AddInstrumentation<TInstrumentation>(Func<TInstrumentation> instrumentationFactory)
+    {
+        Guard.ThrowIfNull(instrumentationFactory);
+
+        this.ConfigureBuilderInternal((sp, builder) =>
+        {
+            builder.AddInstrumentation(instrumentationFactory);
+        });
+
+        return this;
+    }
+
+    /// <inheritdoc />
+    public override MeterProviderBuilder AddMeter(params string[] names)
+    {
+        Guard.ThrowIfNull(names);
+
+        this.ConfigureBuilderInternal((sp, builder) =>
+        {
+            builder.AddMeter(names);
+        });
+
+        return this;
+    }
+
+    /// <inheritdoc />
+    public MeterProviderBuilder ConfigureServices(Action<IServiceCollection> configure)
+        => this.ConfigureServicesInternal(configure);
+
+    /// <inheritdoc cref="IDeferredMeterProviderBuilder.Configure" />
+    public MeterProviderBuilder ConfigureBuilder(Action<IServiceProvider, MeterProviderBuilder> configure)
+        => this.ConfigureBuilderInternal(configure);
+
+    /// <inheritdoc />
+    MeterProviderBuilder IDeferredMeterProviderBuilder.Configure(Action<IServiceProvider, MeterProviderBuilder> configure)
+        => this.ConfigureBuilderInternal(configure);
+
+    private MeterProviderBuilder ConfigureBuilderInternal(Action<IServiceProvider, MeterProviderBuilder> configure)
+    {
+        var services = this.Services
+            ?? throw new NotSupportedException("Builder cannot be configured during MeterProvider construction.");
+
+        services.ConfigureOpenTelemetryMeterProvider(configure);
+
+        return this;
+    }
+
+    private MeterProviderBuilder ConfigureServicesInternal(Action<IServiceCollection> configure)
+    {
+        Guard.ThrowIfNull(configure);
+
+        var services = this.Services
+            ?? throw new NotSupportedException("Services cannot be configured during MeterProvider construction.");
+
+        configure(services);
+
+        return this;
+    }
+}

src/OpenTelemetry.Api.ProviderBuilderExtensions/Metrics/OpenTelemetryDependencyInjectionMetricsServiceCollectionExtensions.cs

@@ -26,44 +26,76 @@ public static class OpenTelemetryDependencyInjectionMetricsServiceCollectionExte
 {
     /// <summary>
     /// Registers an action used to configure the OpenTelemetry <see
-    /// cref="MeterProviderBuilder"/> used to create the <see
-    /// cref="MeterProvider"/> for the <see cref="IServiceCollection"/> being
-    /// configured.
+    /// cref="MeterProviderBuilder"/>.
     /// </summary>
     /// <remarks>
     /// Notes:
     /// <list type="bullet">
     /// <item>This is safe to be called multiple times and by library authors.
     /// Each registered configuration action will be applied
     /// sequentially.</item>
-    /// <item>A <see cref="MeterProvider"/> will not be created automatically
+    /// <item>A <see cref="MeterProvider"/> will NOT be created automatically
     /// using this method. To begin collecting metrics use the
     /// <c>IServiceCollection.AddOpenTelemetry</c> extension in the
     /// <c>OpenTelemetry.Extensions.Hosting</c> package.</item>
     /// </list>
     /// </remarks>
-    /// <param name="services">The <see cref="IServiceCollection" /> to add
-    /// services to.</param>
+    /// <param name="services"><see cref="IServiceCollection" />.</param>
     /// <param name="configure">Callback action to configure the <see
     /// cref="MeterProviderBuilder"/>.</param>
     /// <returns>The <see cref="IServiceCollection"/> so that additional calls
     /// can be chained.</returns>
     public static IServiceCollection ConfigureOpenTelemetryMeterProvider(
         this IServiceCollection services,
-        Action<IServiceProvider, MeterProviderBuilder> configure)
+        Action<MeterProviderBuilder> configure)
     {
-        RegisterBuildAction(services, configure);
+        Guard.ThrowIfNull(services);
+        Guard.ThrowIfNull(configure);
+
+        configure(new MeterProviderServiceCollectionBuilder(services));
 
         return services;
     }
 
-    private static void RegisterBuildAction(IServiceCollection services, Action<IServiceProvider, MeterProviderBuilder> configure)
+    /// <summary>
+    /// Registers an action used to configure the OpenTelemetry <see
+    /// cref="MeterProviderBuilder"/> once the <see cref="IServiceProvider"/>
+    /// is available.
+    /// </summary>
+    /// <remarks>
+    /// Notes:
+    /// <list type="bullet">
+    /// <item>This is safe to be called multiple times and by library authors.
+    /// Each registered configuration action will be applied
+    /// sequentially.</item>
+    /// <item>A <see cref="MeterProvider"/> will NOT be created automatically
+    /// using this method. To begin collecting metrics use the
+    /// <c>IServiceCollection.AddOpenTelemetry</c> extension in the
+    /// <c>OpenTelemetry.Extensions.Hosting</c> package.</item>
+    /// <item>The supplied configuration delegate is called once the <see
+    /// cref="IServiceProvider"/> is available. Services may NOT be added to a
+    /// <see cref="MeterProviderBuilder"/> once the <see
+    /// cref="IServiceProvider"/> has been created. Many helper extensions
+    /// register services and may throw if invoked inside the configuration
+    /// delegate.</item>
+    /// </list>
+    /// </remarks>
+    /// <param name="services"><see cref="IServiceCollection" />.</param>
+    /// <param name="configure">Callback action to configure the <see
+    /// cref="MeterProviderBuilder"/>.</param>
+    /// <returns>The <see cref="IServiceCollection"/> so that additional calls
+    /// can be chained.</returns>
+    public static IServiceCollection ConfigureOpenTelemetryMeterProvider(
+        this IServiceCollection services,
+        Action<IServiceProvider, MeterProviderBuilder> configure)
     {
         Guard.ThrowIfNull(services);
         Guard.ThrowIfNull(configure);
 
         services.AddSingleton<IConfigureMeterProviderBuilder>(
             new ConfigureMeterProviderBuilderCallbackWrapper(configure));
+
+        return services;
     }
 
     private sealed class ConfigureMeterProviderBuilderCallbackWrapper : IConfigureMeterProviderBuilder

src/OpenTelemetry/Metrics/Builder/MeterProviderBuilderBase.cs

@@ -28,7 +28,7 @@ namespace OpenTelemetry.Metrics;
 public class MeterProviderBuilderBase : MeterProviderBuilder, IMeterProviderBuilder
 {
     private readonly bool allowBuild;
-    private IServiceCollection? services;
+    private readonly MeterProviderServiceCollectionBuilder innerBuilder;
 
     public MeterProviderBuilderBase()
     {
@@ -40,9 +40,7 @@ public MeterProviderBuilderBase()
             .TryAddSingleton<MeterProvider>(
                 sp => throw new NotSupportedException("Self-contained MeterProvider cannot be accessed using the application IServiceProvider call Build instead."));
 
-        services.ConfigureOpenTelemetryMeterProvider((sp, builder) => this.services = null);
-
-        this.services = services;
+        this.innerBuilder = new MeterProviderServiceCollectionBuilder(services);
 
         this.allowBuild = true;
     }
@@ -55,9 +53,7 @@ internal MeterProviderBuilderBase(IServiceCollection services)
             .AddOpenTelemetryMeterProviderBuilderServices()
             .TryAddSingleton<MeterProvider>(sp => new MeterProviderSdk(sp, ownsServiceProvider: false));
 
-        services.ConfigureOpenTelemetryMeterProvider((sp, builder) => this.services = null);
-
-        this.services = services;
+        this.innerBuilder = new MeterProviderServiceCollectionBuilder(services);
 
         this.allowBuild = false;
     }
@@ -68,36 +64,26 @@ internal MeterProviderBuilderBase(IServiceCollection services)
     /// <inheritdoc />
     public override MeterProviderBuilder AddInstrumentation<TInstrumentation>(Func<TInstrumentation> instrumentationFactory)
     {
-        Guard.ThrowIfNull(instrumentationFactory);
-
-        this.ConfigureBuilderInternal((sp, builder) =>
-        {
-            builder.AddInstrumentation(instrumentationFactory);
-        });
+        this.innerBuilder.AddInstrumentation(instrumentationFactory);
 
         return this;
     }
 
     /// <inheritdoc />
     public override MeterProviderBuilder AddMeter(params string[] names)
     {
-        Guard.ThrowIfNull(names);
-
-        this.ConfigureBuilderInternal((sp, builder) =>
-        {
-            builder.AddMeter(names);
-        });
+        this.innerBuilder.AddMeter(names);
 
         return this;
     }
 
     /// <inheritdoc />
     MeterProviderBuilder IMeterProviderBuilder.ConfigureServices(Action<IServiceCollection> configure)
-        => this.ConfigureServicesInternal(configure);
+        => this.innerBuilder.ConfigureServices(configure);
 
     /// <inheritdoc />
     MeterProviderBuilder IDeferredMeterProviderBuilder.Configure(Action<IServiceProvider, MeterProviderBuilder> configure)
-        => this.ConfigureBuilderInternal(configure);
+        => this.innerBuilder.ConfigureBuilder(configure);
 
     internal MeterProvider InvokeBuild()
         => this.Build();
@@ -113,14 +99,14 @@ protected MeterProvider Build()
             throw new NotSupportedException("A MeterProviderBuilder bound to external service cannot be built directly. Access the MeterProvider using the application IServiceProvider instead.");
         }
 
-        var services = this.services;
+        var services = this.innerBuilder.Services;
 
         if (services == null)
         {
             throw new NotSupportedException("MeterProviderBuilder build method cannot be called multiple times.");
         }
 
-        this.services = null;
+        this.innerBuilder.Services = null;
 
 #if DEBUG
         bool validateScopes = true;
@@ -131,34 +117,4 @@ protected MeterProvider Build()
 
         return new MeterProviderSdk(serviceProvider, ownsServiceProvider: true);
     }
-
-    private MeterProviderBuilder ConfigureBuilderInternal(Action<IServiceProvider, MeterProviderBuilder> configure)
-    {
-        var services = this.services;
-
-        if (services == null)
-        {
-            throw new NotSupportedException("Builder cannot be configured during MeterProvider construction.");
-        }
-
-        services.ConfigureOpenTelemetryMeterProvider(configure);
-
-        return this;
-    }
-
-    private MeterProviderBuilder ConfigureServicesInternal(Action<IServiceCollection> configure)
-    {
-        Guard.ThrowIfNull(configure);
-
-        var services = this.services;
-
-        if (services == null)
-        {
-            throw new NotSupportedException("Services cannot be configured during MeterProvider construction.");
-        }
-
-        configure(services);
-
-        return this;
-    }
 }

test/OpenTelemetry.Api.ProviderBuilderExtensions.Tests/ServiceCollectionExtensionsTests.cs

@@ -65,26 +65,33 @@ public void ConfigureOpenTelemetryTracerProvider(int numberOfCalls)
     [InlineData(3)]
     public void ConfigureOpenTelemetryMeterProvider(int numberOfCalls)
     {
-        var invocations = 0;
+        var beforeServiceProviderInvocations = 0;
+        var afterServiceProviderInvocations = 0;
 
         var services = new ServiceCollection();
 
         for (int i = 0; i < numberOfCalls; i++)
         {
-            services.ConfigureOpenTelemetryMeterProvider((sp, builder) => invocations++);
+            services.ConfigureOpenTelemetryMeterProvider(builder => beforeServiceProviderInvocations++);
+            services.ConfigureOpenTelemetryMeterProvider((sp, builder) => afterServiceProviderInvocations++);
         }
 
         using var serviceProvider = services.BuildServiceProvider();
 
         var registrations = serviceProvider.GetServices<IConfigureMeterProviderBuilder>();
 
+        Assert.Equal(numberOfCalls, beforeServiceProviderInvocations);
+        Assert.Equal(0, afterServiceProviderInvocations);
+
         foreach (var registration in registrations)
         {
             registration.ConfigureBuilder(serviceProvider, null!);
         }
 
-        Assert.Equal(invocations, registrations.Count());
-        Assert.Equal(numberOfCalls, registrations.Count());
+        Assert.Equal(numberOfCalls, beforeServiceProviderInvocations);
+        Assert.Equal(numberOfCalls, afterServiceProviderInvocations);
+
+        Assert.Equal(numberOfCalls * 2, registrations.Count());
     }
 
     [Theory]
@@ -114,8 +121,4 @@ public void ConfigureOpenTelemetryLoggerProvider(int numberOfCalls)
         Assert.Equal(invocations, registrations.Count());
         Assert.Equal(numberOfCalls, registrations.Count());
     }
-
-    private sealed class CustomType
-    {
-    }
 }