Honour configured logging level

src/Elastic.OpenTelemetry/Diagnostics/DiagnosticErrorLevels.cs

@@ -7,7 +7,30 @@ internal static class DiagnosticErrorLevels
 {
 	public const string Critical = "Critical";
 	public const string Error = "Error";
-	public const string Warning = "Warn";
+	public const string Warning = "Warning";
 	public const string Info = "Info";
 	public const string Trace = "Trace";
+
+	public static LogLevel ToLogLevel(string logLevelString) =>
+		logLevelString switch
+		{
+			Critical => LogLevel.Critical,
+			Error => LogLevel.Error,
+			Warning => LogLevel.Warning,
+			Info => LogLevel.Info,
+			Trace => LogLevel.Trace,
+			_ => LogLevel.Unknown,
+		};
+
+	public static string AsString(this LogLevel logLevel) =>
+		logLevel switch
+		{
+			LogLevel.Critical => Critical,
+			LogLevel.Error => Error,
+			LogLevel.Warning => Warning,
+			LogLevel.Info => Info,
+			LogLevel.Trace => Trace,
+			LogLevel.Unknown => string.Empty,
+			_ => string.Empty
+		};
 }

src/Elastic.OpenTelemetry/Diagnostics/LogFileWriter.cs

@@ -65,7 +65,8 @@ private LogFileWriter()
 
 		foreach (var item in preAmble)
 		{
-			WriteLogPrefix(DiagnosticErrorLevels.Info, builder);
+			// These preamble entries are ALWAYS logged, regardless of the configured log level
+			WriteLogPrefix(LogLevel.Info, builder);
 			builder.Append(item);
 			_streamWriter.WriteLine(builder.ToString());
 			builder.Clear();
@@ -77,17 +78,46 @@ private LogFileWriter()
 		StringBuilderCache.Release(builder);
 	}
 
-	private static void WriteLogPrefix(string logLevel, StringBuilder builder) =>
+	private static readonly LogLevel ConfiguredLogLevel = GetConfiguredLogLevel();
+
+	public static LogLevel GetConfiguredLogLevel()
+	{
+		var logLevel = LogLevel.Info;
+
+		var logLevelEnvironmentVariable = Environment.GetEnvironmentVariable(EnvironmentVariables.ElasticOtelLogLevelEnvironmentVariable);
+
+		if (!string.IsNullOrEmpty(logLevelEnvironmentVariable))
+		{
+			if (logLevelEnvironmentVariable.Equals(DiagnosticErrorLevels.Trace, StringComparison.OrdinalIgnoreCase))
+				logLevel = LogLevel.Trace;
+
+			else if (logLevelEnvironmentVariable.Equals(DiagnosticErrorLevels.Info, StringComparison.OrdinalIgnoreCase))
+				logLevel = LogLevel.Info;
+
+			else if (logLevelEnvironmentVariable.Equals(DiagnosticErrorLevels.Warning, StringComparison.OrdinalIgnoreCase))
+				logLevel = LogLevel.Warning;
+
+			else if (logLevelEnvironmentVariable.Equals(DiagnosticErrorLevels.Error, StringComparison.OrdinalIgnoreCase))
+				logLevel = LogLevel.Error;
+
+			else if (logLevelEnvironmentVariable.Equals(DiagnosticErrorLevels.Critical, StringComparison.OrdinalIgnoreCase))
+				logLevel = LogLevel.Critical;
+		}
+
+		return logLevel;
+	}
+
+	private static void WriteLogPrefix(LogLevel logLevel, StringBuilder builder) =>
 		WriteLogPrefix(Environment.CurrentManagedThreadId, DateTime.UtcNow, logLevel, builder);
 
-	private static void WriteLogPrefix(int managedThreadId, DateTime dateTime, string level, StringBuilder builder)
+	private static void WriteLogPrefix(int managedThreadId, DateTime dateTime, LogLevel level, StringBuilder builder)
 	{
 		builder.Append('[')
 			.Append(dateTime.ToString("yyyy-MM-dd HH:mm:ss.fff"))
 			.Append("][")
 			.Append(managedThreadId == -1 ? "-" : managedThreadId)
 			.Append("][")
-			.Append(level)
+			.Append(level.AsString())
 			.Append(']');
 
 		var length = builder.Length;
@@ -105,20 +135,30 @@ private static void WriteLogPrefix(int managedThreadId, DateTime dateTime, strin
 
 	public Task WritingTask { get; }
 
+	public void WriteCriticalLogLine(IDiagnosticEvent diagnosticEvent, string message) =>
+		WriteLogLine(diagnosticEvent, LogLevel.Critical, message);
+
 	public void WriteErrorLogLine(IDiagnosticEvent diagnosticEvent, string message) =>
-		WriteLogLine(diagnosticEvent, DiagnosticErrorLevels.Error, message);
+		WriteLogLine(diagnosticEvent, LogLevel.Error, message);
+
+	public void WriteWarningLogLine(IDiagnosticEvent diagnosticEvent, string message) =>
+		WriteLogLine(diagnosticEvent, LogLevel.Warning, message);
 
 	public void WriteInfoLogLine(IDiagnosticEvent diagnosticEvent, string message) =>
-		WriteLogLine(diagnosticEvent, DiagnosticErrorLevels.Info, message);
+		WriteLogLine(diagnosticEvent, LogLevel.Info, message);
 
 	public void WriteTraceLogLine(IDiagnosticEvent diagnosticEvent, string message) =>
-		WriteLogLine(diagnosticEvent, DiagnosticErrorLevels.Trace, message);
+		WriteLogLine(diagnosticEvent, LogLevel.Trace, message);
 
-	public void WriteLogLine(IDiagnosticEvent diagnosticEvent, string logLevel, string message) =>
+	public void WriteLogLine(IDiagnosticEvent diagnosticEvent, LogLevel logLevel, string message) =>
 		WriteLogLine(diagnosticEvent.Activity, diagnosticEvent.ManagedThreadId, diagnosticEvent.DateTime, logLevel, message);
 
-	public void WriteLogLine(Activity? activity, int managedThreadId, DateTime dateTime, string logLevel, string logLine)
+	public void WriteLogLine(Activity? activity, int managedThreadId, DateTime dateTime, LogLevel logLevel, string logLine)
 	{
+		// We skip logging for any log level higher (numerically) than the configured log level
+		if (logLevel > ConfiguredLogLevel)
+			return;
+
 		var builder = StringBuilderCache.Acquire();
 		WriteLogPrefix(managedThreadId, dateTime, logLevel, builder);
 		builder.Append(logLine);

src/Elastic.OpenTelemetry/Diagnostics/LogLevel.cs

@@ -0,0 +1,14 @@
+// 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.Diagnostics;
+
+internal enum LogLevel
+{
+	Unknown = 0,
+	Critical = 1,
+	Error = 2,
+	Warning = 3,
+	Info = 4,
+	Trace = 5
+}

src/Elastic.OpenTelemetry/Diagnostics/LoggingEventListener.cs

@@ -17,20 +17,17 @@ public LoggingEventListener(LogFileWriter logFileWriter)
     {
 		_logFileWriter = logFileWriter;
 
-		var eventLevel = Environment.GetEnvironmentVariable(EnvironmentVariables.ElasticOtelLogLevelEnvironmentVariable);
+		var eventLevel = LogFileWriter.GetConfiguredLogLevel();
 
-		if (!string.IsNullOrEmpty(eventLevel))
+		_eventLevel = eventLevel switch
 		{
-			_eventLevel = eventLevel.ToLowerInvariant() switch
-			{
-				"trace" => EventLevel.Verbose,
-				"info" => EventLevel.Informational,
-				"warning" => EventLevel.Warning,
-				"error" => EventLevel.Error,
-				"critical" => EventLevel.Critical,
-				_ => EventLevel.Informational // fallback to info level
-			};
-		}
+			LogLevel.Trace => EventLevel.Verbose,
+			LogLevel.Info => EventLevel.Informational,
+			LogLevel.Warning => EventLevel.Warning,
+			LogLevel.Error => EventLevel.Error,
+			LogLevel.Critical => EventLevel.Critical,
+			_ => EventLevel.Informational // fallback to info level
+		};
 	}
 
 	public override void Dispose()
@@ -70,24 +67,24 @@ protected override void OnEventWritten(EventWrittenEventArgs eventData)
 			// TODO - We can only get the OS thread ID from the args - Do we send that instead??
 			// As per this issue - https://github.com/dotnet/runtime/issues/13125 - OnEventWritten may be on a different thread
 			// so we can't use the Environment.CurrentManagedThreadId value here.
-			_logFileWriter.WriteLogLine(null, -1, eventData.TimeStamp, GetLevel(eventData), StringBuilderCache.GetStringAndRelease(builder));
+			_logFileWriter.WriteLogLine(null, -1, eventData.TimeStamp, GetLogLevel(eventData), StringBuilderCache.GetStringAndRelease(builder));
 		}
 		catch (Exception)
 		{
 			// TODO - We might want to block writing further events if we reach here as it's
 			// likely a file access issue
 		}
 
-		static string GetLevel(EventWrittenEventArgs eventData) =>
+		static LogLevel GetLogLevel(EventWrittenEventArgs eventData) =>
 			eventData.Level switch
 			{
-				EventLevel.Critical => DiagnosticErrorLevels.Critical,
-				EventLevel.Error => DiagnosticErrorLevels.Error,
-				EventLevel.Warning => DiagnosticErrorLevels.Warning,
-				EventLevel.Informational => DiagnosticErrorLevels.Info,
-				EventLevel.Verbose => DiagnosticErrorLevels.Trace,
-				EventLevel.LogAlways => "N/A",
-				_ => throw new Exception("Unhandled event data level")
+				EventLevel.Critical => LogLevel.Critical,
+				EventLevel.Error => LogLevel.Error,
+				EventLevel.Warning => LogLevel.Warning,
+				EventLevel.Informational => LogLevel.Info,
+				EventLevel.Verbose => LogLevel.Trace,
+				EventLevel.LogAlways => LogLevel.Unknown,
+				_ => LogLevel.Unknown
 			};
 
 		static void CreateLogMessage(EventWrittenEventArgs eventData, StringBuilder builder)