[otlp] Use LogRecord.Logger.Name for instrumentation scope if LogRecord.CategoryName is null (#5300)

Co-authored-by: Mikel Blanchard <[email protected]>

Author: AB027PS

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/CHANGELOG.md

@@ -21,6 +21,11 @@
   experimental Logs Bridge API.
   ([#5268](https://github.com/open-telemetry/opentelemetry-dotnet/pull/5268))
 
+* Updated `OtlpLogExporter` to set instrumentation scope name on the data model
+  from `LogRecord.Logger.Name` if `LogRecord.CategoryName` is `null`. This is
+  typically the case when using the experimental Logs Bridge API.
+  ([#5300](https://github.com/open-telemetry/opentelemetry-dotnet/pull/5300))
+
 ## 1.7.0
 
 Released 2023-Dec-08

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

@@ -18,6 +18,8 @@ internal sealed class OtlpLogRecordTransformer
 {
     internal static readonly ConcurrentBag<OtlpLogs.ScopeLogs> LogListPool = new();
 
+    private const string DefaultScopeName = "";
+
     private readonly SdkLimitOptions sdkLimitOptions;
     private readonly ExperimentalOptions experimentalOptions;
 
@@ -47,10 +49,11 @@ internal OtlpCollector.ExportLogsServiceRequest BuildExportRequest(
             var otlpLogRecord = this.ToOtlpLog(logRecord);
             if (otlpLogRecord != null)
             {
-                if (!logsByCategory.TryGetValue(logRecord.CategoryName, out var scopeLogs))
+                var scopeName = logRecord.CategoryName ?? logRecord.Logger?.Name ?? DefaultScopeName;
+                if (!logsByCategory.TryGetValue(scopeName, out var scopeLogs))
                 {
-                    scopeLogs = this.GetLogListFromPool(logRecord.CategoryName);
-                    logsByCategory.Add(logRecord.CategoryName, scopeLogs);
+                    scopeLogs = this.GetLogListFromPool(scopeName);
+                    logsByCategory.Add(scopeName, scopeLogs);
                     resourceLogs.ScopeLogs.Add(scopeLogs);
                 }
 

test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpLogExporterTests.cs

@@ -1469,6 +1469,44 @@ public void VerifyEnvironmentVariablesTakenFromIConfigurationWhenUsingLoggingBui
             });
     }
 
+    [Theory]
+    [InlineData("my_instrumentation_scope_name", "my_instrumentation_scope_name")]
+    [InlineData(null, "")]
+    public void LogRecordLoggerNameIsExportedWhenUsingBridgeApi(string loggerName, string expectedScopeName)
+    {
+        LogRecordAttributeList attributes = default;
+        attributes.Add("name", "tomato");
+        attributes.Add("price", 2.99);
+        attributes.Add("{OriginalFormat}", "Hello from {name} {price}.");
+
+        var logRecords = new List<LogRecord>();
+
+        using (var loggerProvider = Sdk.CreateLoggerProviderBuilder()
+                   .AddInMemoryExporter(logRecords)
+                   .Build())
+        {
+            var logger = loggerProvider.GetLogger(loggerName);
+
+            logger.EmitLog(new LogRecordData());
+        }
+
+        Assert.Single(logRecords);
+
+        var otlpLogRecordTransformer = new OtlpLogRecordTransformer(DefaultSdkLimitOptions, new());
+
+        var batch = new Batch<LogRecord>(new[] { logRecords[0] }, 1);
+
+        var request = otlpLogRecordTransformer.BuildExportRequest(
+            new Proto.Resource.V1.Resource(),
+            batch);
+
+        Assert.NotNull(request);
+        Assert.Single(request.ResourceLogs);
+        Assert.Single(request.ResourceLogs[0].ScopeLogs);
+
+        Assert.Equal(expectedScopeName, request.ResourceLogs[0].ScopeLogs[0].Scope?.Name);
+    }
+
     private static void RunVerifyEnvironmentVariablesTakenFromIConfigurationTest(
         string optionsName,
         Func<Action<IServiceCollection>, (IDisposable Container, ILoggerFactory LoggerFactory)> createLoggerFactoryFunc)