src/Elastic.Apm/Api/Tracer.cs

@@ -21,7 +21,7 @@ internal class Tracer : ITracer
 	{
 		private readonly IApmServerInfo _apmServerInfo;
 		private readonly IConfigurationSnapshotProvider _configurationProvider;
-		private readonly ScopedLogger _logger;
+		private readonly IApmLogger _logger;
 		private readonly IPayloadSender _sender;
 		private readonly Service _service;
 		private readonly BreakdownMetricsProvider _breakdownMetricsProvider;
@@ -83,7 +83,7 @@ private Transaction StartTransactionInternal(string name, string type, Distribut
 				traceId: traceId, links: links, current: current)
 			{ Service = _service };
 
-			_logger.Debug()?.Log("Starting {TransactionValue}", retVal);
+			_logger?.Debug()?.Log("{Scope} Starting {TransactionValue}", nameof(Tracer), retVal);
 			return retVal;
 		}
 

src/Elastic.Apm/Config/Net4FullFramework/AppSettingsConfigurationKeyValueProvider.cs

@@ -3,8 +3,8 @@
 // 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
 
-#if NETFRAMEWORK
 #nullable enable
+#if NETFRAMEWORK
 using System.Configuration;
 using Elastic.Apm.Logging;
 
@@ -14,8 +14,7 @@ internal class AppSettingsConfigurationKeyValueProvider : IConfigurationKeyValue
 {
 	private readonly IApmLogger? _logger;
 
-	public AppSettingsConfigurationKeyValueProvider(IApmLogger? logger) =>
-		_logger = logger?.Scoped(nameof(AppSettingsConfigurationKeyValueProvider));
+	public AppSettingsConfigurationKeyValueProvider(IApmLogger? logger) => _logger = logger?.Scoped(nameof(AppSettingsConfigurationKeyValueProvider));
 
 	public string Description => nameof(AppSettingsConfigurationKeyValueProvider);
 
@@ -29,9 +28,10 @@ public AppSettingsConfigurationKeyValueProvider(IApmLogger? logger) =>
 		}
 		catch (ConfigurationErrorsException ex)
 		{
-			_logger.Error()?.LogException(ex, "Exception thrown from ConfigurationManager.AppSettings - falling back on environment variables");
+			_logger?.Error()?.LogException(ex, "Exception thrown from ConfigurationManager.AppSettings - falling back on environment variables");
 		}
 		return null;
 	}
 }
 #endif
+#nullable restore

src/Elastic.Apm/Logging/IApmLoggingExtensions.cs

@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information
 
 using System;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
@@ -12,13 +13,49 @@
 
 namespace Elastic.Apm.Logging;
 
+#nullable enable
 internal static class LoggingExtensions
 {
-	private static ConditionalWeakTable<string, LogValuesFormatter> Formatters { get; } = new();
+	// Using a ConcurrentDictionary rather than ConditionalWeakTable as we expect few distinct scopes
+	// and we want to retain them for reuse across the application lifetime.
+	private static readonly ConcurrentDictionary<string, ScopedLogger> ScopedLoggers = new();
 
-	internal static ScopedLogger Scoped(this IApmLogger logger, string scope) => new(logger is ScopedLogger s ? s.Logger : logger, scope);
+	private static readonly ConditionalWeakTable<string, LogValuesFormatter> Formatters = new();
 
-	private static void DoLog(this IApmLogger logger, LogLevel level, string message, Exception e, params object[] args)
+	/// <summary>
+	/// Returns a ScopedLogger, potentially from the cache.
+	/// </summary>
+	/// <param name="logger">An existing <see cref="IApmLogger"/>.</param>
+	/// <param name="scope">The name of the scope.</param>
+	/// <returns>A new scoped logger or <c>null</c> of the <see cref="IApmLogger"/> is <c>null</c>.</returns>
+	/// <exception cref="ArgumentException">Requires <paramref name="scope"/> to be non-null and non-empty.</exception>
+	internal static ScopedLogger? Scoped(this IApmLogger? logger, string scope)
+	{
+		if (string.IsNullOrEmpty(scope))
+			throw new ArgumentException("Scope is required to be non-null and non-empty.", nameof(scope));
+
+		if (logger is null)
+			return null;
+
+		if (!ScopedLoggers.TryGetValue(scope, out var scopedLogger))
+		{
+			// Ensure we don't allow creations of scoped loggers 'wrapping' other scoped loggers
+			var potentialScopedLogger = new ScopedLogger(logger is ScopedLogger s ? s.Logger : logger, scope);
+
+			if (ScopedLoggers.TryAdd(scope, potentialScopedLogger))
+			{
+				scopedLogger = potentialScopedLogger;
+			}
+			else
+			{
+				scopedLogger = ScopedLoggers[scope];
+			}
+		}
+
+		return scopedLogger;
+	}
+
+	private static void DoLog(this IApmLogger logger, LogLevel level, string message, Exception? exception, params object?[]? args)
 	{
 		try
 		{
@@ -28,9 +65,9 @@ private static void DoLog(this IApmLogger logger, LogLevel level, string message
 
 			var logValues = formatter.GetState(args);
 
-			logger?.Log(level, logValues, e, static (l, _) => l.Formatter.Format(l.Args));
+			logger?.Log(level, logValues, exception, static (l, _) => l.Formatter.Format(l.Args));
 		}
-		catch (Exception exception)
+		catch (Exception ex)
 		{
 			// For now we will just print it to System.Diagnostics.Trace
 			// In the future we should consider error counters to increment and log periodically on a worker thread
@@ -44,12 +81,12 @@ private static void DoLog(this IApmLogger logger, LogLevel level, string message
 
 				System.Diagnostics.Trace.WriteLine("Elastic APM .NET Agent: [CRITICAL] Exception thrown by logging implementation."
 					+ $" Log message: `{message.AsNullableToString()}'."
-					+ $" args.Length: {args.Length}."
+					+ $" args.Length: {args?.Length ?? 0}."
 					+ $" Current thread: {DbgUtils.CurrentThreadDesc}"
 					+ newLine
-					+ $"+-> Exception (exception): {exception.GetType().FullName}: {exception.Message}{newLine}{exception.StackTrace}"
-					+ (e != null
-						? newLine + $"+-> Exception (e): {e.GetType().FullName}: {e.Message}{newLine}{e.StackTrace}"
+					+ $"+-> Exception (exception): {ex.GetType().FullName}: {ex.Message}{newLine}{ex.StackTrace}"
+					+ (exception != null
+						? newLine + $"+-> Exception (e): {exception.GetType().FullName}: {exception.Message}{newLine}{exception.StackTrace}"
 						: $"e: {ObjectExtensions.NullAsString}")
 					+ newLine
 					+ "+-> Current stack trace:" + currentStackTrace
@@ -62,11 +99,11 @@ private static void DoLog(this IApmLogger logger, LogLevel level, string message
 		}
 	}
 
-#if !NET6_0_OR_GREATER
+#if !NET8_0_OR_GREATER
 	private static readonly object _lock = new();
 #endif
 
-	private static LogValuesFormatter GetOrAddFormatter(string message, IReadOnlyCollection<object> args)
+	private static LogValuesFormatter GetOrAddFormatter(string message, IReadOnlyCollection<object?>? args)
 	{
 		if (Formatters.TryGetValue(message, out var formatter))
 			return formatter;
@@ -162,7 +199,7 @@ internal readonly struct MaybeLogger
 
 		public MaybeLogger(IApmLogger logger, LogLevel level) => (_logger, _level) = (logger, level);
 
-		public void Log(string message, params object[] args) => _logger.DoLog(_level, message, null, args);
+		public void Log(string message, params object?[]? args) => _logger.DoLog(_level, message, null, args);
 
 		public void LogException(Exception exception, string message, params object[] args) =>
 			_logger.DoLog(_level, message, exception, args);
@@ -179,3 +216,4 @@ public void LogExceptionWithCaller(Exception exception,
 		}
 	}
 }
+#nullable restore

src/Elastic.Apm/Logging/ScopedLogger.cs

@@ -16,7 +16,7 @@ internal class ScopedLogger : IApmLogger
 
 	public IApmLogger Logger { get; }
 
-#if !NET6_0_OR_GREATER
+#if !NET8_0_OR_GREATER
 	private readonly object _lock = new();
 #endif
 

src/Elastic.Apm/Metrics/MetricsProvider/BreakdownMetricsProvider.cs

@@ -17,7 +17,7 @@ internal class BreakdownMetricsProvider : IMetricsProvider
 		/// <summary>
 		/// Encapsulates types which are used as key to group MetricSets.
 		/// </summary>
-		private struct GroupKey
+		private readonly record struct GroupKey
 		{
 			public TransactionInfo Transaction { get; }
 			public SpanInfo Span { get; }

src/Elastic.Apm/Model/Error.cs

@@ -20,16 +20,14 @@ internal class Error : IError
 		[JsonIgnore]
 		internal IConfiguration Configuration { get; }
 
-		public Error(CapturedException capturedException, Transaction transaction, string parentId, IApmLogger loggerArg, Dictionary<string, Label> labels = null
-		)
-			: this(transaction, parentId, loggerArg, labels) => Exception = capturedException;
+		public Error(CapturedException capturedException, Transaction transaction, string parentId, IApmLogger loggerArg, Dictionary<string, Label> labels = null) :
+			this(transaction, parentId, loggerArg, labels) => Exception = capturedException;
 
 		public Error(ErrorLog errorLog, Transaction transaction, string parentId, IApmLogger loggerArg, Dictionary<string, Label> labels = null) :
 			this(transaction, parentId, loggerArg, labels)
-			=> Log = errorLog;
-
+				=> Log = errorLog;
 
-		private Error(Transaction transaction, string parentId, IApmLogger loggerArg, Dictionary<string, Label> labels = null)
+		private Error(Transaction transaction, string parentId, IApmLogger logger, Dictionary<string, Label> labels = null)
 		{
 			Timestamp = TimeUtils.TimestampNow();
 			Id = RandomGenerator.GenerateRandomBytesAsString(new byte[16]);
@@ -57,9 +55,7 @@ private Error(Transaction transaction, string parentId, IApmLogger loggerArg, Di
 
 			CheckAndCaptureBaggage(transaction);
 
-			IApmLogger logger = loggerArg?.Scoped($"{nameof(Error)}.{Id}");
-			logger.Trace()
-				?.Log("New Error instance created: {Error}. Time: {Time} (as timestamp: {Timestamp})",
+			logger?.Scoped(nameof(Error))?.Trace()?.Log("New Error instance created: {Error}. Time: {Time} (as timestamp: {Timestamp})",
 					this, TimeUtils.FormatTimestampForLog(Timestamp), Timestamp);
 		}
 

src/Elastic.Apm/Model/Span.cs

@@ -72,16 +72,16 @@ public Span(string name,
 			Activity current = null
 		)
 		{
-			InstrumentationFlag = instrumentationFlag;
-			Timestamp = timestamp ?? TimeUtils.TimestampNow();
-			Id = id ?? RandomGenerator.GenerateRandomBytesAsString(new byte[8]);
-			_logger = logger?.Scoped($"{nameof(Span)}.{Id}");
-
+			_logger = logger?.Scoped(nameof(Span));
 			_payloadSender = payloadSender;
 			_currentExecutionSegmentsContainer = currentExecutionSegmentsContainer;
 			_parentSpan = parentSpan;
 			_enclosingTransaction = enclosingTransaction;
 			_apmServerInfo = apmServerInfo;
+
+			InstrumentationFlag = instrumentationFlag;
+			Timestamp = timestamp ?? TimeUtils.TimestampNow();
+			Id = id ?? ActivitySpanId.CreateRandom().ToString();
 			IsExitSpan = isExitSpan;
 			Name = name;
 			Type = type;
@@ -123,9 +123,10 @@ public Span(string name,
 
 			_currentExecutionSegmentsContainer.CurrentSpan = this;
 
-			_logger.Trace()
-				?.Log("New Span instance created: {Span}. Start time: {Time} (as timestamp: {Timestamp}). Parent span: {Span}",
-					this, TimeUtils.FormatTimestampForLog(Timestamp), Timestamp, _parentSpan);
+			var formattedTimestamp = _logger.IsEnabled(LogLevel.Trace) ? TimeUtils.FormatTimestampForLog(Timestamp) : string.Empty;
+
+			_logger?.Trace()?.Log("New Span instance created: {Span}. Start time: {Time} (as timestamp: {Timestamp}). Parent span: {Span}",
+				this, formattedTimestamp, Timestamp, _parentSpan);
 		}
 
 		private void CheckAndCaptureBaggage()
@@ -138,7 +139,7 @@ private void CheckAndCaptureBaggage()
 				if (!WildcardMatcher.IsAnyMatch(Configuration.BaggageToAttach, baggage.Key))
 					continue;
 
-				Otel ??= new OTel { Attributes = new Dictionary<string, object>() };
+				Otel ??= new OTel { Attributes = [] };
 
 				var newKey = $"baggage.{baggage.Key}";
 				Otel.Attributes[newKey] = baggage.Value;
@@ -392,17 +393,18 @@ internal Span StartSpanInternal(string name, string type, string subType = null,
 			string id = null, bool isExitSpan = false, IEnumerable<SpanLink> links = null, Activity current = null
 		)
 		{
-			var retVal = new Span(name, type, Id, TraceId, _enclosingTransaction, _payloadSender, _logger, _currentExecutionSegmentsContainer,
+			var span = new Span(name, type, Id, TraceId, _enclosingTransaction, _payloadSender, _logger, _currentExecutionSegmentsContainer,
 				_apmServerInfo, this, instrumentationFlag, captureStackTraceOnStart, timestamp, isExitSpan, id, links, current: current);
 
 			if (!string.IsNullOrEmpty(subType))
-				retVal.Subtype = subType;
+				span.Subtype = subType;
 
 			if (!string.IsNullOrEmpty(action))
-				retVal.Action = action;
+				span.Action = action;
 
-			_logger.Trace()?.Log("Starting {SpanDetails}", retVal.ToString());
-			return retVal;
+			_logger?.Trace()?.Log("Starting {SpanDetails}", span.ToString());
+
+			return span;
 		}
 
 		/// <summary>
@@ -416,12 +418,13 @@ public void End()
 			if (Outcome == Outcome.Unknown && !_outcomeChangedThroughApi)
 				Outcome = Outcome.Success;
 
+			var formattedTimestamp = _logger.IsEnabled(LogLevel.Trace) ? TimeUtils.FormatTimestampForLog(Timestamp) : string.Empty;
+
 			if (Duration.HasValue)
 			{
-				_logger.Trace()
-					?.Log("Ended {Span} (with Duration already set)." +
+				_logger?.Trace()?.Log("Ended {Span} (with Duration already set)." +
 						" Start time: {Time} (as timestamp: {Timestamp}), Duration: {Duration}ms",
-						this, TimeUtils.FormatTimestampForLog(Timestamp), Timestamp, Duration);
+						this, formattedTimestamp, Timestamp, Duration);
 
 				if (_parentSpan != null)
 					_parentSpan?._childDurationTimer.OnChildEnd((long)(Timestamp + Duration.Value * 1000));
@@ -448,10 +451,9 @@ public void End()
 
 				_childDurationTimer.OnSpanEnd(endTimestamp);
 
-				_logger.Trace()
-					?.Log("Ended {Span}. Start time: {Time} (as timestamp: {Timestamp})," +
+				_logger?.Trace()?.Log("Ended {Span}. Start time: {Time} (as timestamp: {Timestamp})," +
 						" End time: {Time} (as timestamp: {Timestamp}), Duration: {Duration}ms",
-						this, TimeUtils.FormatTimestampForLog(Timestamp), Timestamp,
+						this, formattedTimestamp, Timestamp,
 						TimeUtils.FormatTimestampForLog(endTimestamp), endTimestamp, Duration);
 			}
 
@@ -473,7 +475,7 @@ public void End()
 			}
 			catch (Exception e)
 			{
-				_logger.Warning()?.LogException(e, "Failed deducing destination fields for span.");
+				_logger?.Warning()?.LogException(e, "Failed deducing destination fields for span.");
 			}
 
 			if (_isDropped && _context.IsValueCreated)
@@ -570,7 +572,7 @@ void QueueSpan(Span span)
 									DroppedSpanStatCache.Value.DestinationServiceResource, _outcome, Duration!.Value);
 								break;
 						}
-						_logger.Trace()?.Log("Dropping fast exit span on composite span. Composite duration: {duration}", Composite.Sum);
+						_logger?.Trace()?.Log("Dropping fast exit span on composite span. Composite duration: {duration}", Composite.Sum);
 						return;
 					}
 					if (span.Duration < span.Configuration.ExitSpanMinDuration)
@@ -587,7 +589,7 @@ void QueueSpan(Span span)
 									DroppedSpanStatCache.Value.DestinationServiceResource, _outcome, Duration!.Value);
 								break;
 						}
-						_logger.Trace()?.Log("Dropping fast exit span. Duration: {duration}", Duration);
+						_logger?.Trace()?.Log("Dropping fast exit span. Duration: {duration}", Duration);
 						return;
 					}
 				}
@@ -869,8 +871,7 @@ private Destination DeduceHttpDestination()
 			}
 			catch (Exception ex)
 			{
-				_logger.Trace()
-					?.LogException(ex, "Failed to deduce destination info from Context.Http."
+				_logger?.Trace()?.LogException(ex, "Failed to deduce destination info from Context.Http."
 						+ " Original URL: {OriginalUrl}. Context.Http.Url: {Context.Http.Url}."
 						, Context.Http.OriginalUrl, Context.Http.Url);
 				return null;

src/Elastic.Apm/Model/SpanTimerKey.cs

@@ -8,12 +8,14 @@ namespace Elastic.Apm.Model
 	/// <summary>
 	/// Encapsulates type and subtype
 	/// </summary>
-	internal struct SpanTimerKey
+	internal readonly record struct SpanTimerKey
 	{
 		public SpanTimerKey(string type, string subType) => (Type, SubType) = (type, subType);
 		public SpanTimerKey(string type) => (Type, SubType) = (type, null);
-		public string Type { get; }
-		public string SubType { get; set; }
-		public static SpanTimerKey AppSpanType => new SpanTimerKey("app");
+
+		public readonly string Type { get; }
+		public readonly string SubType { get; }
+
+		public static SpanTimerKey AppSpanType => new("app");
 	}
 }