Ensure correct execution order for user-provided delegates

examples/Example.Console/Example.Console.csproj

@@ -9,8 +9,8 @@
 
     <ItemGroup>
       <PackageReference Include="Microsoft.Extensions.Logging.Console" Version="9.0.3" />
-      <PackageReference Include="OpenTelemetry.Exporter.Console" Version="1.12.0" />
-      <PackageReference Include="OpenTelemetry.Instrumentation.StackExchangeRedis" Version="1.12.0-beta.1" />
+      <PackageReference Include="OpenTelemetry.Exporter.Console" Version="1.13.0" />
+      <PackageReference Include="OpenTelemetry.Instrumentation.StackExchangeRedis" Version="1.13.0-beta.1" />
     </ItemGroup>
 
     <ItemGroup>

examples/Example.MinimalApi/CustomProcessor.cs

@@ -0,0 +1,18 @@
+// Licensed to Elasticsearch B.V under one or more agreements.
+// Elasticsearch B.V licenses this file to you under the Apache 2.0 License.
+// See the LICENSE file in the project root for more information
+
+using System.Diagnostics;
+using OpenTelemetry;
+
+namespace Example.MinimalApi;
+
+public class CustomProcessor : BaseProcessor<Activity>
+{
+	public override void OnEnd(Activity data)
+	{
+		Thread.Sleep(1000); // Enough time for the export to have happened
+
+		data.SetTag("custom-processor-tag", "ProcessedByCustomProcessor");
+	}
+}

examples/Example.MinimalApi/Example.MinimalApi.csproj

@@ -1,9 +1,10 @@
-<Project Sdk="Microsoft.NET.Sdk.Web">
+<Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
     <Nullable>enable</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
+    <UserSecretsId>4b1d6eb4-a323-4148-8195-1ec759984c7d</UserSecretsId>
   </PropertyGroup>
 
   <ItemGroup>
@@ -12,7 +13,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="OpenTelemetry.Instrumentation.AspNetCore" Version="1.12.0" />
+    <PackageReference Include="OpenTelemetry.Instrumentation.AspNetCore" Version="1.13.0" />
   </ItemGroup>
 
 </Project>

examples/Example.MinimalApi/Program.cs

@@ -5,18 +5,41 @@
 using System.Diagnostics;
 using Example.MinimalApi;
 using OpenTelemetry;
+using OpenTelemetry.Exporter;
+using OpenTelemetry.Trace;
 
 var builder = WebApplication.CreateBuilder(args);
 
-//builder.AddElasticOpenTelemetry();
+var options = new Elastic.OpenTelemetry.ElasticOpenTelemetryOptions()
+{
+	// You can customize options here if needed
+};
 
-// This will add the OpenTelemetry services using Elastic defaults
-builder.AddServiceDefaults();
+//// Force small batch size and no delay for quicker exports in this example
+builder.Services.Configure<OtlpExporterOptions>(o =>
+{
+	o.BatchExportProcessorOptions.MaxExportBatchSize = 1;
+	o.BatchExportProcessorOptions.ScheduledDelayMilliseconds = 1;
+});
+
+//builder.Services.AddOpenTelemetry()
+//	.WithTracing(t => t
+//		.WithElasticDefaults(builder.Configuration, t => t
+//			.AddSource(Api.ActivitySourceName)
+//			.AddProcessor(new CustomProcessor())));
+
+builder.Services.AddOpenTelemetry()
+	.WithElasticTracing(builder.Configuration, t => t
+			.AddSource(Api.ActivitySourceName)
+			.AddProcessor(new CustomProcessor()));
+
+// Preferred method to add Elastic OpenTelemetry integration
+//builder.AddElasticOpenTelemetry(options, otelBuilder => otelBuilder
+//	.WithTracing(t => t
+//		.AddSource(Api.ActivitySourceName)
+//		.AddProcessor(new CustomProcessor())));
 
-builder.Services
-	.AddHttpClient() // Adds IHttpClientFactory
-	.AddElasticOpenTelemetry() // Adds app specific tracing
-		.WithTracing(t => t.AddSource(Api.ActivitySourceName));
+builder.AddServiceDefaults();
 
 var app = builder.Build();
 

examples/ServiceDefaults/Extensions.cs

@@ -18,7 +18,7 @@ public static class Extensions
 {
 	public static IHostApplicationBuilder AddServiceDefaults(this IHostApplicationBuilder builder)
 	{
-		builder.ConfigureOpenTelemetry();
+		//builder.ConfigureOpenTelemetry();
 
 		builder.AddDefaultHealthChecks();
 
@@ -49,8 +49,6 @@ public static IHostApplicationBuilder ConfigureOpenTelemetry(this IHostApplicati
 				}
 			});
 
-		builder.AddOpenTelemetryExporters();
-
 		return builder;
 	}
 

examples/ServiceDefaults/ServiceDefaults.csproj

@@ -1,21 +1,21 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net9.0</TargetFramework>
+    <TargetFrameworks>net8.0;net9.0</TargetFrameworks>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
     <IsAspireSharedProject>true</IsAspireSharedProject>
   </PropertyGroup>
 
   <ItemGroup>
     <FrameworkReference Include="Microsoft.AspNetCore.App" />
-
+    
     <PackageReference Include="Microsoft.Extensions.Http.Resilience" Version="9.1.0" />
     <PackageReference Include="Microsoft.Extensions.ServiceDiscovery" Version="9.0.0" />
-    <PackageReference Include="OpenTelemetry.Exporter.OpenTelemetryProtocol" Version="1.12.0" />
-    <PackageReference Include="OpenTelemetry.Extensions.Hosting" Version="1.12.0" />
-    <PackageReference Include="OpenTelemetry.Instrumentation.GrpcNetClient" Version="1.12.0-beta.1" />
-    <PackageReference Include="OpenTelemetry.Instrumentation.Process" Version="1.12.0-beta.1" />
+    <PackageReference Include="OpenTelemetry.Exporter.OpenTelemetryProtocol" Version="1.13.1" />
+    <PackageReference Include="OpenTelemetry.Extensions.Hosting" Version="1.13.0" />
+    <PackageReference Include="OpenTelemetry.Instrumentation.GrpcNetClient" Version="1.13.0-beta.1" />
+    <PackageReference Include="OpenTelemetry.Instrumentation.Process" Version="1.13.0-beta.1" />
   </ItemGroup>
 
   <ItemGroup>

src/Elastic.OpenTelemetry.AutoInstrumentation/AutoInstrumentationPlugin.cs

@@ -43,6 +43,7 @@ public TracerProviderBuilder BeforeConfigureTracerProvider(TracerProviderBuilder
 			builder.ConfigureResource(r => r.WithElasticDefaultsCore(_components, null, null));
 
 			builder.ConfigureServices(sc => sc.Configure<OtlpExporterOptions>(OtlpExporterDefaults.OtlpExporterOptions));
+			logger.LogConfiguredOtlpExporterOptions();
 
 			TracerProvderBuilderExtensions.AddActivitySourceWithLogging(builder, logger, "Elastic.Transport", "<n/a>");
 			TracerProvderBuilderExtensions.AddElasticProcessorsCore(builder, null, _components, null);
@@ -74,6 +75,7 @@ public MeterProviderBuilder BeforeConfigureMeterProvider(MeterProviderBuilder bu
 			builder.ConfigureServices(sc => sc
 				.Configure<OtlpExporterOptions>(OtlpExporterDefaults.OtlpExporterOptions)
 				.Configure<MetricReaderOptions>(o => o.TemporalityPreference = MetricReaderTemporalityPreference.Delta));
+			logger.LogConfiguredOtlpExporterOptions();
 
 			logger.LogConfiguredSignalProvider(nameof(Signals.Metrics), nameof(MeterProviderBuilder), "<n/a>");
 
@@ -91,8 +93,7 @@ public MeterProviderBuilder BeforeConfigureMeterProvider(MeterProviderBuilder bu
 	/// <summary>
 	/// To configure logs SDK (the method name is the same as for other logs options).
 	/// </summary>
-	public void ConfigureLogsOptions(OpenTelemetryLoggerOptions options) =>
-		options.WithElasticDefaults(_components.Logger);
+	public void ConfigureLogsOptions(OpenTelemetryLoggerOptions options) => options.WithElasticDefaults(_components.Logger);
 
 	/// <summary>
 	/// To configure Resource.

src/Elastic.OpenTelemetry.Core/BuilderContext.cs

@@ -0,0 +1,21 @@
+// Licensed to Elasticsearch B.V under one or more agreements.
+// Elasticsearch B.V licenses this file to you under the Apache 2.0 License.
+// See the LICENSE file in the project root for more information
+
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Elastic.OpenTelemetry.Core;
+
+/// <summary>
+/// This is used internally to pass context around during the fluent builder configuration process.
+/// </summary>
+internal sealed class BuilderContext<T> where T : class
+{
+	internal required T Builder { get; init; }
+
+	internal required BuilderState BuilderState { get; init; }
+
+	internal required BuilderOptions<T> BuilderOptions { get; init; }
+
+	internal IServiceCollection? Services { get; init; }
+}

src/Elastic.OpenTelemetry.Core/BuilderOptions.cs

@@ -0,0 +1,9 @@
+// Licensed to Elasticsearch B.V under one or more agreements.
+// Elasticsearch B.V licenses this file to you under the Apache 2.0 License.
+// See the LICENSE file in the project root for more information
+
+namespace Elastic.OpenTelemetry.Core;
+
+internal readonly record struct BuilderOptions<T>(
+	Action<T>? UserProvidedConfigureBuilder,
+	bool DeferAddOtlpExporter) where T : class;

src/Elastic.OpenTelemetry.Core/Diagnostics/CompositeLogger.cs

@@ -4,7 +4,6 @@
 
 using Elastic.OpenTelemetry.Configuration;
 using Elastic.OpenTelemetry.Core;
-using Elastic.OpenTelemetry.Diagnostics;
 using Microsoft.Extensions.Logging;
 
 namespace Elastic.OpenTelemetry.Diagnostics;

src/Elastic.OpenTelemetry.Core/Diagnostics/DeferredLogger.cs

@@ -0,0 +1,101 @@
+// Licensed to Elasticsearch B.V under one or more agreements.
+// Elasticsearch B.V licenses this file to you under the Apache 2.0 License.
+// See the LICENSE file in the project root for more information
+
+using System.Collections.Concurrent;
+using System.Diagnostics.CodeAnalysis;
+using Elastic.OpenTelemetry.Configuration;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Logging.Abstractions;
+
+namespace Elastic.OpenTelemetry.Diagnostics;
+
+/// <summary>
+/// Used to capture log entries before the file logger is initialized.
+/// </summary>
+/// <remarks>
+/// Log entries are stored in a concurrent queue and drained to the first file logger that is available.
+/// Log entries are only captured if file logging is enabled in the options.
+/// </remarks>
+internal sealed class DeferredLogger : ILogger
+{
+	private readonly bool _isEnabled = false;
+	private readonly LogLevel _configuredLogLevel;
+	private readonly ConcurrentQueue<string> _logQueue = new();
+	private readonly ILogger? _additionalLogger;
+
+	/// <summary>
+	/// Create an instance of <see cref="DeferredLogger"/>.
+	/// </summary>
+	/// <param name="options">The options used to configure the logger.</param>
+	/// <param name="additionalLogger">An optional additional logger to which log entries will be written. For example,
+	/// this may be available in ASP.NET Core scenarios and ensures the early log entries are sent to other sinks, such
+	/// as the console, when available.</param>
+	private DeferredLogger(CompositeElasticOpenTelemetryOptions options, ILogger? additionalLogger = null)
+	{
+		_isEnabled = options.GlobalLogEnabled && options.LogTargets.HasFlag(LogTargets.File);
+		_configuredLogLevel = options.LogLevel;
+
+		if (!_isEnabled)
+			return;
+
+		_additionalLogger = additionalLogger;
+	}
+
+	public IDisposable BeginScope<TState>(TState state) where TState : notnull => NullScope.Instance;
+
+	public bool IsEnabled(LogLevel logLevel) => _isEnabled && _configuredLogLevel <= logLevel;
+
+	public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception? exception, Func<TState, Exception?, string> formatter)
+	{
+		if (!IsEnabled(logLevel))
+			return;
+
+		var logLine = LogFormatter.Format(logLevel, eventId, state, exception, formatter);
+
+		if (exception is not null)
+			logLine = $"{logLine}{Environment.NewLine}{exception}";
+
+		_logQueue.Enqueue(logLine);
+
+		_additionalLogger?.Log(logLevel, eventId, state, exception, formatter);
+	}
+
+	internal void DrainLogQueue(StreamWriter streamWriter)
+	{
+		while (_logQueue.TryDequeue(out var deferredLog))
+		{
+			streamWriter.WriteLine(deferredLog);
+		}
+	}
+
+	private static DeferredLogger? Instance;
+
+	internal static ILogger GetOrCreate(CompositeElasticOpenTelemetryOptions options)
+	{
+		// We want, at most, one instance of DeferredLogger for the application.
+		// We only create a DeferredFileLogger if file logging is enabled
+		if (options.GlobalLogEnabled && options.LogTargets.HasFlag(LogTargets.File))
+			return Instance ??= new DeferredLogger(options, options.AdditionalLogger);
+
+		return NullLogger.Instance;
+	}
+
+	internal static bool TryGetInstance([NotNullWhen(true)] out DeferredLogger? instance)
+	{
+		instance = Instance;
+		return instance is not null;
+	}
+
+	internal static void ReleaseInstance() => Instance = null;
+
+	private class NullScope : IDisposable
+	{
+		public static readonly NullScope Instance = new();
+
+		public void Dispose()
+		{
+			// No-op
+		}
+	}
+}

src/Elastic.OpenTelemetry.Core/Diagnostics/FileLogger.cs

@@ -17,13 +17,12 @@ internal sealed class FileLogger : IDisposable, IAsyncDisposable, ILogger
 	private readonly CancellationTokenSource _cancellationTokenSource = new();
 	private readonly StreamWriter _streamWriter;
 	private readonly LogLevel _configuredLogLevel;
+	private readonly LoggerExternalScopeProvider _scopeProvider;
 
 	private bool _disposed;
 
 	public bool FileLoggingEnabled { get; }
 
-	private readonly LoggerExternalScopeProvider _scopeProvider;
-
 	public FileLogger(CompositeElasticOpenTelemetryOptions options)
 	{
 		_scopeProvider = new LoggerExternalScopeProvider();
@@ -40,8 +39,8 @@ public FileLogger(CompositeElasticOpenTelemetryOptions options)
 		{
 			var process = Process.GetCurrentProcess();
 
-			// When ordered by filename, we see logs from the same process grouped, then ordered by oldest to newest, then the PID for that instance
-			var logFileName = $"EDOT.{process.ProcessName}_{DateTimeOffset.UtcNow.ToUnixTimeMilliseconds()}_{process.Id}.log";
+			// This naming resembles the naming structure for OpenTelemetry log files.
+			var logFileName = $"edot-dotnet-{process.Id}-{process.ProcessName}-{DateTimeOffset.UtcNow:yyyyMMdd-hhMMssfffZ}.log";
 			var logDirectory = options.LogDirectory;
 
 			LogFilePath = Path.Combine(logDirectory, logFileName);
@@ -50,13 +49,21 @@ public FileLogger(CompositeElasticOpenTelemetryOptions options)
 				Directory.CreateDirectory(logDirectory);
 
 			// StreamWriter.Dispose disposes underlying stream too.
-			var stream = new FileStream(LogFilePath, FileMode.OpenOrCreate, FileAccess.Write);
+			var stream = new FileStream(LogFilePath, FileMode.Append, FileAccess.Write, FileShare.Read);
 
 			_streamWriter = new StreamWriter(stream, Encoding.UTF8);
 
 			_streamWriter.WriteLine("DateTime (UTC)           Thread  SpanId  Level         Message");
 			_streamWriter.WriteLine();
 
+			// Drain any deferred log entries captured before the file logger was initialized.
+			// These appear before the preamble to ensure correct timestamping order.
+			if (DeferredLogger.TryGetInstance(out var deferredLogger))
+			{
+				deferredLogger.DrainLogQueue(_streamWriter);
+				DeferredLogger.ReleaseInstance();
+			}
+
 			WritingTask = Task.Run(async () =>
 			{
 				var cancellationToken = _cancellationTokenSource.Token;