Convert StateValues (when present) to Attributes. (#2554)

Author: ndrwrbgs

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+* Changed `OtlpLogExporter` to convert `ILogger` structured log inputs to
+  `Attributes` in OpenTelemetry (only active when `ParseStateValues` is `true`
+  on `OpenTelemetryLoggerOptions`)
+
 ## Unreleased
 
 * Added validation that insecure channel is configured correctly when using

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/LogRecordExtensions.cs

@@ -76,16 +76,25 @@ internal static OtlpLogs.LogRecord ToOtlpLog(this LogRecord logRecord)
                 otlpLogRecord.Body = new OtlpCommon.AnyValue { StringValue = logRecord.FormattedMessage };
             }
 
+            if (logRecord.StateValues != null)
+            {
+                foreach (var stateValue in logRecord.StateValues)
+                {
+                    var otlpAttribute = stateValue.ToOtlpAttribute();
+                    otlpLogRecord.Attributes.Add(otlpAttribute);
+                }
+            }
+
             if (logRecord.EventId != 0)
             {
-                otlpLogRecord.Attributes.AddAttribute(nameof(logRecord.EventId), logRecord.EventId.ToString());
+                otlpLogRecord.Attributes.AddStringAttribute(nameof(logRecord.EventId), logRecord.EventId.ToString());
             }
 
             if (logRecord.Exception != null)
             {
-                otlpLogRecord.Attributes.AddAttribute(SemanticConventions.AttributeExceptionType, logRecord.Exception.GetType().Name);
-                otlpLogRecord.Attributes.AddAttribute(SemanticConventions.AttributeExceptionMessage, logRecord.Exception.Message);
-                otlpLogRecord.Attributes.AddAttribute(SemanticConventions.AttributeExceptionStacktrace, logRecord.Exception.ToInvariantString());
+                otlpLogRecord.Attributes.AddStringAttribute(SemanticConventions.AttributeExceptionType, logRecord.Exception.GetType().Name);
+                otlpLogRecord.Attributes.AddStringAttribute(SemanticConventions.AttributeExceptionMessage, logRecord.Exception.Message);
+                otlpLogRecord.Attributes.AddStringAttribute(SemanticConventions.AttributeExceptionStacktrace, logRecord.Exception.ToInvariantString());
             }
 
             if (logRecord.TraceId != default && logRecord.SpanId != default)
@@ -107,7 +116,7 @@ internal static OtlpLogs.LogRecord ToOtlpLog(this LogRecord logRecord)
             return otlpLogRecord;
         }
 
-        private static void AddAttribute(this RepeatedField<OtlpCommon.KeyValue> repeatedField, string key, string value)
+        private static void AddStringAttribute(this RepeatedField<OtlpCommon.KeyValue> repeatedField, string key, string value)
         {
             repeatedField.Add(new OtlpCommon.KeyValue
             {