Proposal for Elastic.Apm.Agent instantiation

sample/SampleAspNetCoreApp/Startup.cs

@@ -1,4 +1,5 @@
-using Elastic.Apm.AspNetCore;
+using Elastic.Apm;
+using Elastic.Apm.AspNetCore;
 using Elastic.Apm.DiagnosticSource;
 using Elastic.Apm.EntityFrameworkCore;
 using Microsoft.AspNetCore.Builder;
@@ -38,9 +39,7 @@ public void ConfigureServices(IServiceCollection services)
 		// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
 		public void Configure(IApplicationBuilder app, IHostingEnvironment env)
 		{
-			app.UseElasticApm(Configuration);
-			new ElasticCoreListeners().Start();
-			new ElasticEntityFrameworkCoreListener().Start();
+			app.UseElasticApm(Configuration, new HttpDiagnosticsSubscriber(), new EfCoreDiagnosticsSubscriber());
 
 			if (env.IsDevelopment())
 				app.UseDeveloperExceptionPage();

src/Elastic.Apm.AspNetCore/ApmMiddleware.cs

@@ -2,6 +2,9 @@
 using System.Reflection;
 using System.Runtime.CompilerServices;
 using System.Threading.Tasks;
+using Elastic.Apm.Api;
+using Elastic.Apm.AspNetCore.Config;
+using Elastic.Apm.Config;
 using Elastic.Apm.Helpers;
 using Elastic.Apm.Model.Payload;
 using Microsoft.AspNetCore.Http;
@@ -19,29 +22,17 @@ namespace Elastic.Apm.AspNetCore
 	public class ApmMiddleware
 	{
 		private readonly RequestDelegate _next;
+		private readonly ITracer _tracer;
 
-		public ApmMiddleware(RequestDelegate next)
+		public ApmMiddleware(RequestDelegate next, ITracer tracer)
 		{
 			_next = next;
-
-			var service = new Service
-			{
-				Agent = new Service.AgentC
-				{
-					Name = Consts.AgentName,
-					Version = Consts.AgentVersion
-				},
-				Name = Assembly.GetEntryAssembly()?.GetName().Name,
-				Framework = new Framework { Name = "ASP.NET Core", Version = "2.1" }, //TODO: Get version
-				Language = new Language { Name = "C#" } //TODO
-			};
-
-			Agent.Tracer.Service = service;
+			_tracer = tracer;
 		}
 
 		public async Task InvokeAsync(HttpContext context)
 		{
-			var transaction = Agent.Tracer.StartTransaction($"{context.Request.Method} {context.Request.Path}",
+			var transaction = _tracer.StartTransaction($"{context.Request.Method} {context.Request.Path}",
 				Transaction.TypeRequest);
 
 			transaction.Context = new Context

src/Elastic.Apm.AspNetCore/ApmMiddlewareExtension.cs

@@ -1,8 +1,10 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
+using System.Reflection;
 using Elastic.Apm.AspNetCore.Config;
 using Elastic.Apm.AspNetCore.DiagnosticListener;
 using Elastic.Apm.DiagnosticSource;
-using Elastic.Apm.Report;
+using Elastic.Apm.Model.Payload;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.Extensions.Configuration;
 
@@ -20,18 +22,40 @@ public static class ApmMiddlewareExtension
 		/// doing this the agent will read agent related configurations through this IConfiguration instance.
 		/// </param>
 		/// <param name="payloadSender">Payload sender.</param>
+		/// <param name="subscribers">Specify which diagnostic source subscribers you want to connect</param>
 		public static IApplicationBuilder UseElasticApm(
-			this IApplicationBuilder builder, IConfiguration configuration = null, IPayloadSender payloadSender = null
+			this IApplicationBuilder builder,
+			IConfiguration configuration = null,
+			params IDiagnosticsSubscriber[] subscribers
 		)
 		{
-			if (configuration != null) Agent.Config = new MicrosoftExtensionsConfig(configuration);
-
-			if (payloadSender != null) Agent.PayloadSender = payloadSender;
-
-			System.Diagnostics.DiagnosticListener.AllListeners
-				.Subscribe(new DiagnosticInitializer(new List<IDiagnosticListener> { new AspNetCoreDiagnosticListener() }));
+			var service = new Service
+			{
+				Agent = new Service.AgentC
+				{
+					Name = Consts.AgentName,
+					Version = Consts.AgentVersion
+				},
+				Name = Assembly.GetEntryAssembly()?.GetName().Name,
+				Framework = new Framework { Name = "ASP.NET Core", Version = "2.1" }, //TODO: Get version
+				Language = new Language { Name = "C#" } //TODO
+			};
+			var configReader = configuration != null ? new MicrosoftExtensionsConfig(configuration) : null;
+			var config = new AgentComponents(configurationReader: configReader, service: service);
+			Agent.Setup(config);
+			return UseElasticApm(builder, Agent.Instance, subscribers);
+		}
 
-			return builder.UseMiddleware<ApmMiddleware>();
+		internal static IApplicationBuilder UseElasticApm(
+			this IApplicationBuilder builder,
+			ApmAgent agent,
+			params IDiagnosticsSubscriber[] subscribers
+		)
+		{
+			var subs = new List<IDiagnosticsSubscriber>(subscribers ?? Array.Empty<IDiagnosticsSubscriber>());
+			subs.Add(new AspNetCoreDiagnosticsSubscriber());
+			agent.Subscribe(subs.ToArray());
+			return builder.UseMiddleware<ApmMiddleware>(agent.Tracer);
 		}
 	}
 }

src/Elastic.Apm.AspNetCore/Config/MicrosoftExtensionsConfig.cs

@@ -1,4 +1,9 @@
-using Elastic.Apm.Config;
+using System;
+using System.Collections.Generic;
+using Elastic.Apm.Config;
+using Elastic.Apm.Logging;
+using Elastic.Apm.Model.Payload;
+using Elastic.Apm.Report;
 using Microsoft.Extensions.Configuration;
 
 namespace Elastic.Apm.AspNetCore.Config
@@ -7,54 +12,60 @@ namespace Elastic.Apm.AspNetCore.Config
 	/// An agent-config provider based on Microsoft.Extensions.Configuration.IConfiguration.
 	/// It uses environment variables as fallback
 	/// </summary>
-	public class MicrosoftExtensionsConfig : AbstractAgentConfig
+	public class MicrosoftExtensionsConfig : AbstractConfigurationReader, IConfigurationReader
 	{
 		private readonly IConfiguration _configuration;
 
-		public MicrosoftExtensionsConfig(IConfiguration configuration)
+		internal const string Origin = "Configuration Provider";
+
+		public static (string LevelSubKey, string Level, string Urls) Keys = (
+			LevelSubKey: "LogLevel",
+			Level: $"ElasticApm:LogLevel",
+			Urls: "ElasticApm:ServerUrls"
+		);
+
+		public MicrosoftExtensionsConfig(IConfiguration configuration, AbstractLogger logger = null) : base(logger)
 		{
 			_configuration = configuration;
-			_configuration.GetSection("ElasticApm")
-				?
+			_configuration.GetSection("ElasticApm")?
 				.GetReloadToken()
 				.RegisterChangeCallback(ChangeCallback, configuration.GetSection("ElasticApm"));
 		}
 
-
-		protected override (string value, string configType, string configKey) ReadServerUrls()
+		private LogLevel? _logLevel;
+		public LogLevel LogLevel
 		{
-			var configValue = _configuration[MicrosoftExtensionConfigConsts.ServerUrls];
-			return string.IsNullOrEmpty(configValue)
-				? (_configuration[EnvVarConsts.ServerUrls], "environment variable", EnvVarConsts.ServerUrls)
-				: (configValue, "IConfiguration", MicrosoftExtensionConfigConsts.ServerUrls);
+			get
+			{
+				if (_logLevel.HasValue) return _logLevel.Value;
+
+				var l = ParseLogLevel(ReadFallBack(Keys.Level, EnvironmentConfigurationReader.Keys.Level));
+				_logLevel = l;
+				return l;
+			}
 		}
 
-		protected override (string value, string configType, string configKey) ReadLogLevel()
+		public IReadOnlyList<Uri> ServerUrls => ParseServerUrls(ReadFallBack(Keys.Urls, EnvironmentConfigurationReader.Keys.Urls));
+
+		private ConfigurationKeyValue Read(string key) => Kv(key, _configuration[key], Origin);
+
+		private ConfigurationKeyValue ReadFallBack(string key, string fallBack)
 		{
-			var configValue = _configuration[MicrosoftExtensionConfigConsts.LogLevel];
-			return string.IsNullOrEmpty(configValue)
-				? (_configuration[EnvVarConsts.LogLevel], "environment variable", EnvVarConsts.LogLevel)
-				: (configValue, "IConfiguration", MicrosoftExtensionConfigConsts.LogLevel);
+			var primary = Read(key);
+			if (!string.IsNullOrWhiteSpace(primary.Value)) return primary;
+			var secondary = Kv(key, _configuration[fallBack], EnvironmentConfigurationReader.Origin);
+			return secondary;
 		}
 
 		private void ChangeCallback(object obj)
 		{
-			var (newLogLevel, isError)
-				= ParseLogLevel((obj as IConfigurationSection)?[MicrosoftExtensionConfigConsts.LogLevel.Split(':')[1]]);
+			if (!(obj is IConfigurationSection section)) return;
 
-			if (!isError && newLogLevel.HasValue && newLogLevel.Value != LogLevelBackingField)
-			{
-				LogLevelBackingField = newLogLevel;
-				Logger?.LogInfo($"Updated log level to {LogLevelBackingField.ToString()}");
-			}
+			var newLogLevel = ParseLogLevel(Kv(Keys.LevelSubKey, section[Keys.LevelSubKey], Origin));
+			if (_logLevel.HasValue && newLogLevel == _logLevel.Value) return;
 
-			if (isError) Logger?.LogInfo($"Updating log level failed, current log level: {LogLevelBackingField.ToString()}");
+			_logLevel = newLogLevel;
+			Logger?.LogInfo($"Updated log level to {newLogLevel}");
 		}
 	}
-
-	internal static class MicrosoftExtensionConfigConsts
-	{
-		public static string LogLevel => "ElasticApm:LogLevel";
-		public static string ServerUrls => "ElasticApm:ServerUrls";
-	}
 }

src/Elastic.Apm.AspNetCore/DiagnosticListener/AspNetCoreDiagnosticListener.cs

@@ -11,8 +11,7 @@ public class AspNetCoreDiagnosticListener : IDiagnosticListener
 	{
 		private readonly AbstractLogger _logger;
 
-		public AspNetCoreDiagnosticListener()
-			=> _logger = Agent.CreateLogger(Name);
+		public AspNetCoreDiagnosticListener(IApmAgent agent) => _logger = agent.Logger;
 
 		public string Name => "Microsoft.AspNetCore";
 

src/Elastic.Apm.AspNetCore/DiagnosticListener/HttpDiagnosticsSubscriber.cs

@@ -0,0 +1,23 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using Elastic.Apm.Config;
+using Elastic.Apm.DiagnosticListeners;
+using Elastic.Apm.DiagnosticSource;
+using Elastic.Apm.Logging;
+
+namespace Elastic.Apm.AspNetCore.DiagnosticListener
+{
+	/// <summary>
+	/// Manages all listeners that are generated by Types which are part of .netstandard 2.0
+	/// </summary>
+	public class AspNetCoreDiagnosticsSubscriber : IDiagnosticsSubscriber
+	{
+		/// <summary>
+		/// Start listening for diagnosticsource events. Only listens for sources that are part of the Agent.Core package.
+		/// </summary>
+		public IDisposable Subscribe(IApmAgent agent) => System.Diagnostics.DiagnosticListener
+			.AllListeners
+			.Subscribe(new DiagnosticInitializer(new [] { new AspNetCoreDiagnosticListener(agent),  }));
+	}
+}

src/Elastic.Apm.EntityFrameworkCore/EfCoreDiagnosticListener.cs

@@ -4,6 +4,7 @@
 using System.Data;
 using Elastic.Apm.Api;
 using Elastic.Apm.DiagnosticSource;
+using Elastic.Apm.Logging;
 using Elastic.Apm.Model.Payload;
 using Microsoft.EntityFrameworkCore.Diagnostics;
 
@@ -12,6 +13,11 @@ namespace Elastic.Apm.EntityFrameworkCore
 	internal class EfCoreDiagnosticListener : IDiagnosticListener
 	{
 		private readonly ConcurrentDictionary<Guid, ISpan> _spans = new ConcurrentDictionary<Guid, ISpan>();
+
+		public EfCoreDiagnosticListener(IApmAgent agent) => Logger = agent.Logger;
+
+		private AbstractLogger Logger { get; }
+
 		public string Name => "Microsoft.EntityFrameworkCore";
 
 		public void OnCompleted() { }

src/Elastic.Apm.EntityFrameworkCore/EfCoreDiagnosticsSubscriber.cs

@@ -0,0 +1,22 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using Elastic.Apm.Config;
+using Elastic.Apm.DiagnosticSource;
+using Elastic.Apm.Logging;
+
+namespace Elastic.Apm.EntityFrameworkCore
+{
+	/// <summary>
+	/// Manages the Entity Framework Core listener, which listenes to EF Core events
+	/// </summary>
+	public class EfCoreDiagnosticsSubscriber : IDiagnosticsSubscriber
+	{
+		/// <summary>
+		/// Start listening for EF Core diagnosticsource events
+		/// </summary>
+		public IDisposable Subscribe(IApmAgent agentComponents) => DiagnosticListener
+			.AllListeners
+			.Subscribe(new DiagnosticInitializer(new [] { new EfCoreDiagnosticListener(agentComponents) }));
+	}
+}