Add diagnostics, file logging and ILogger integration

Directory.Build.props

@@ -18,6 +18,7 @@
     <UseArtifactsOutput>true</UseArtifactsOutput>
     <SolutionRoot>$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), build.bat))</SolutionRoot>
     <ArtifactsPath>$(MSBuildThisFileDirectory).artifacts</ArtifactsPath>
+    <ExposedPublicKey>002400000480000094000000060200000024000052534131000400000100010015b0fa59d868c7f3ea2ae67567b19e102465745f01b430a38a42b92fd41a0f5869bec1f2b33b589d78662af432fe6b789ef72d4738f7b1a86264d7aeb5185ed8995b2bb104e7c5c58845f1a618be829e410fa34a6bd7d714ece191ed68a66333a83ae7456ee32e9aeb54bc1d7410ae8c344367257e9001abb5e96ce1f1d97696</ExposedPublicKey>
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="MinVer" Version="4.3.0" PrivateAssets="all" />

examples/Example.Elastic.OpenTelemetry.Worker/Program.cs

@@ -4,9 +4,10 @@
 using Example.Elastic.OpenTelemetry.Worker;
 
 var builder = Host.CreateApplicationBuilder(args);
-builder.Services.AddHostedService<Worker>();
 
-builder.Services.AddElasticOpenTelemetry("CustomActivitySource");
+builder.EnableElasticOpenTelemetry("CustomActivitySource");
+
+builder.Services.AddHostedService<Worker>();
 
 var host = builder.Build();
 host.Run();

examples/Example.Elastic.OpenTelemetry.Worker/appsettings.Development.json

@@ -2,7 +2,8 @@
   "Logging": {
     "LogLevel": {
       "Default": "Information",
-      "Microsoft.Hosting.Lifetime": "Information"
+      "Microsoft.Hosting.Lifetime": "Information",
+      "Elastic": "Trace"
     }
   }
 }

src/Elastic.OpenTelemetry/Agent.cs

@@ -1,97 +1,145 @@
 // 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 OpenTelemetry;
 using System.Reflection;
+using Microsoft.Extensions.Logging;
+
+using static Elastic.OpenTelemetry.Diagnostics.ElasticOpenTelemetryDiagnosticSource;
 
 namespace Elastic.OpenTelemetry;
 
 /// <summary>
 /// Supports building and accessing an <see cref="IAgent"/> which collects and ships observability signals.
 /// </summary>
-public static class Agent
+public static partial class Agent
 {
-    private static readonly object Lock = new();
-    private static IAgent? _current;
-
-    static Agent()
-    {
-        var assemblyInformationalVersion = typeof(Agent).Assembly.GetCustomAttribute<AssemblyInformationalVersionAttribute>()?.InformationalVersion;
-        InformationalVersion = ParseAssemblyInformationalVersion(assemblyInformationalVersion);
-    }
-
-    /// <summary>
-    /// Returns the singleton <see cref="IAgent"/> instance.
-    /// </summary>
-    /// <remarks>
-    /// If an instance is not already initialized, this will create and return a
-    /// default <see cref="IAgent"/> configured with recommended Elastic defaults.
-    /// </remarks>
-    public static IAgent Current
-    {
-        get
-        {
-            if (_current is not null) return _current;
-
-            lock (Lock)
-            {
-                // disable to satisfy double check lock pattern analyzer
-                // ReSharper disable once InvertIf
-                if (_current is null)
-                {
-                    var agent = new AgentBuilder().Build();
-                    _current = agent;
-                }
-                return _current;
-            }
-        }
-    }
-
-    internal static string InformationalVersion { get; }
-
-    /// <summary>
-    /// Builds an <see cref="IAgent"/>.
-    /// </summary>
-    /// <returns>An <see cref="IAgent"/> instance.</returns>
-    /// <exception cref="Exception">
-    /// An exception will be thrown if <see cref="Build"/>
-    /// is called more than once during the lifetime of an application.
-    /// </exception>
-    public static IAgent Build(Action<AgentBuilder>? configuration = null)
-    {
-        if (_current != null)
-            throw new Exception($"{nameof(Agent)}.{nameof(Build)} called twice or after {nameof(Agent)}.{nameof(Current)} was accessed.");
-
-        lock (Lock)
-        {
-            if (_current != null)
-                throw new Exception($"{nameof(Agent)}.{nameof(Build)} called twice or after {nameof(Agent)}.{nameof(Current)} was accessed.");
-
-            var agentBuilder = new AgentBuilder();
-            configuration?.Invoke(agentBuilder);
-            var agent = agentBuilder.Build();
-            _current = agent;
-            return _current;
-        }
-    }
-
-    internal static string ParseAssemblyInformationalVersion(string? informationalVersion)
-    {
-        if (string.IsNullOrWhiteSpace(informationalVersion))
-        {
-            informationalVersion = "1.0.0";
-        }
-
-        /*
-         * InformationalVersion will be in the following format:
-         *   {majorVersion}.{minorVersion}.{patchVersion}.{pre-release label}.{pre-release version}.{gitHeight}+{Git SHA of current commit}
-         * Ex: 1.5.0-alpha.1.40+807f703e1b4d9874a92bd86d9f2d4ebe5b5d52e4
-         * The following parts are optional: pre-release label, pre-release version, git height, Git SHA of current commit
-         */
-
-        var indexOfPlusSign = informationalVersion!.IndexOf('+');
-        return indexOfPlusSign > 0
-            ? informationalVersion[..indexOfPlusSign]
-            : informationalVersion;
-    }
+	private static readonly object Lock = new();
+	private static IAgent? CurrentAgent;
+
+	static Agent()
+	{
+		var assemblyInformationalVersion = typeof(Agent).Assembly.GetCustomAttribute<AssemblyInformationalVersionAttribute>()?.InformationalVersion;
+		InformationalVersion = ParseAssemblyInformationalVersion(assemblyInformationalVersion);
+	}
+
+	/// <summary>
+	/// Returns the singleton <see cref="IAgent"/> instance.
+	/// </summary>
+	/// <remarks>
+	/// If an instance is not already initialized, this will create and return a
+	/// default <see cref="IAgent"/> configured with recommended Elastic defaults.
+	/// </remarks>
+	public static IAgent Current
+	{
+		get
+		{
+			if (CurrentAgent is not null)
+				return CurrentAgent;
+
+			lock (Lock)
+			{
+				// disable to satisfy double check lock pattern analyzer
+				// ReSharper disable once InvertIf
+				if (CurrentAgent is null)
+				{
+					var agent = new AgentBuilder().Build();
+					CurrentAgent = agent;
+				}
+				return CurrentAgent;
+			}
+		}
+	}
+
+	internal static string InformationalVersion { get; }
+
+	/// <summary>
+	/// Builds an <see cref="IAgent"/>.
+	/// </summary>
+	/// <returns>An <see cref="IAgent"/> instance.</returns>
+	/// <exception cref="Exception">
+	/// An exception will be thrown if <see cref="Build"/>
+	/// is called more than once during the lifetime of an application.
+	/// </exception>
+	public static IAgent Build(Action<AgentBuilder>? configuration = null)
+	{
+		CheckCurrent();
+
+		lock (Lock)
+		{
+			CheckCurrent();
+			var agentBuilder = new AgentBuilder();
+			configuration?.Invoke(agentBuilder);
+			var agent = agentBuilder.Build();
+			CurrentAgent = agent;
+			return CurrentAgent;
+		}
+
+		static void CheckCurrent()
+		{
+			if (CurrentAgent is not null)
+			{
+				Log(AgentBuildCalledMultipleTimesEvent);
+				throw new Exception();
+			}
+		}
+	}
+
+	internal const string BuildErrorMessage = $"{nameof(Agent)}.{nameof(Build)} called twice or after " +
+		$"{nameof(Agent)}.{nameof(Current)} was accessed.";
+
+	internal const string SetAgentErrorMessage = $"{nameof(Agent)}.{nameof(SetAgent)} called twice" +
+		$"or after {nameof(Agent)}.{nameof(Build)} or after {nameof(Agent)}.{nameof(Current)} was accessed.";
+
+	[LoggerMessage(EventId = 1, Level = LogLevel.Error, Message = SetAgentErrorMessage)]
+	internal static partial void SetAgentError(this ILogger logger);
+
+	/// <summary>
+	/// TODO
+	/// </summary>
+	/// <param name="agent"></param>
+	/// <param name="logger"></param>
+	/// <returns></returns>
+	/// <exception cref="Exception"></exception>
+	internal static IAgent SetAgent(IAgent agent, ILogger logger)
+	{
+		CheckCurrent(logger);
+
+		lock (Lock)
+		{
+			CheckCurrent(logger);
+			logger.LogInformation($"Setting {nameof(CurrentAgent)}.");
+			CurrentAgent = agent;
+			return CurrentAgent;
+		}
+
+		static void CheckCurrent(ILogger logger)
+		{
+			if (CurrentAgent is not null)
+			{
+				Log(AgentSetAgentCalledMultipleTimesEvent);
+				logger.SetAgentError();
+				throw new Exception(SetAgentErrorMessage);
+			}
+		}
+	}
+
+	internal static string ParseAssemblyInformationalVersion(string? informationalVersion)
+	{
+		if (string.IsNullOrWhiteSpace(informationalVersion))
+		{
+			informationalVersion = "1.0.0";
+		}
+
+		/*
+		 * InformationalVersion will be in the following format:
+		 *   {majorVersion}.{minorVersion}.{patchVersion}.{pre-release label}.{pre-release version}.{gitHeight}+{Git SHA of current commit}
+		 * Ex: 1.5.0-alpha.1.40+807f703e1b4d9874a92bd86d9f2d4ebe5b5d52e4
+		 * The following parts are optional: pre-release label, pre-release version, git height, Git SHA of current commit
+		 */
+
+		var indexOfPlusSign = informationalVersion!.IndexOf('+');
+		return indexOfPlusSign > 0
+			? informationalVersion[..indexOfPlusSign]
+			: informationalVersion;
+	}
 }