fix(otel logging): Include ILogger CategoryName in logger output

sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/LogsHelper.cs

@@ -124,6 +124,12 @@ internal static List<TelemetryItem> OtelToAzureMonitorLogs(Batch<LogRecord> batc
 
             logRecord.ForEachScope(s_processScope, properties);
 
+            var categoryName = logRecord.CategoryName;
+            if (!string.IsNullOrEmpty(categoryName))
+            {
+                properties.Add("CategoryName", categoryName.Truncate(SchemaConstants.KVP_MaxValueLength)!);
+            }
+
             if (logRecord.EventId.Id != 0)
             {
                 properties.Add("EventId", logRecord.EventId.Id.ToString(CultureInfo.InvariantCulture));

sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/tests/Azure.Monitor.OpenTelemetry.Exporter.Tests/E2ETelemetryItemValidation/LogsTests.cs

@@ -83,7 +83,7 @@ public void VerifyLog(LogLevel logLevel, string expectedSeverityLevel)
                 telemetryItem: telemetryItem!,
                 expectedSeverityLevel: expectedSeverityLevel,
                 expectedMessage: "Hello {name}.",
-                expectedMessageProperties: new Dictionary<string, string> { { "name", "World" }},
+                expectedMessageProperties: new Dictionary<string, string> { { "name", "World" }, { "CategoryName", logCategoryName } },
                 expectedSpanId: null,
                 expectedTraceId: null);
         }

sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/tests/Azure.Monitor.OpenTelemetry.Exporter.Tests/LogsHelperTests.cs

@@ -61,7 +61,7 @@ public void MessageIsSetToExceptionMessage(bool parseStateValues)
             Assert.Equal("tomato", name);
             Assert.True(properties.TryGetValue("price", out string price));
             Assert.Equal("2.99", price);
-            Assert.Equal(3, properties.Count);
+            Assert.Equal(4, properties.Count);
         }
 
         [Fact]
@@ -91,7 +91,7 @@ public void MessageIsSetToFormattedMessageWhenIncludeFormattedMessageIsSet()
             Assert.Equal("tomato", name);
             Assert.True(properties.TryGetValue("price", out string price));
             Assert.Equal("2.99", price);
-            Assert.Equal(2, properties.Count);
+            Assert.Equal(3, properties.Count);
         }
 
         [Fact]
@@ -121,7 +121,7 @@ public void MessageIsSetToOriginalFormatWhenIncludeFormattedMessageIsNotSet()
             Assert.Equal("tomato", name);
             Assert.True(properties.TryGetValue("price", out string price));
             Assert.Equal("2.99", price);
-            Assert.Equal(2, properties.Count);
+            Assert.Equal(3, properties.Count);
         }
 
         [Theory]
@@ -152,7 +152,7 @@ public void PropertiesContainFieldsFromStructuredLogs(bool parseStateValues)
             Assert.Equal("tomato", name);
             Assert.True(properties.TryGetValue("price", out string price));
             Assert.Equal("2.99", price);
-            Assert.Equal(2, properties.Count);
+            Assert.Equal(3, properties.Count);
         }
 
         [Fact]
@@ -180,7 +180,65 @@ public void PropertiesContainEventIdAndEventNameIfSetOnLog()
             Assert.Equal("1", eventId);
             Assert.True(properties.TryGetValue("EventName", out string eventName));
             Assert.Equal("TestEvent", eventName);
-            Assert.Equal(2, properties.Count);
+            Assert.Equal(3, properties.Count);
+        }
+
+        [Fact]
+        public void PropertiesContainLoggerCategoryName()
+        {
+            var logRecords = new List<LogRecord>();
+            using var loggerFactory = LoggerFactory.Create(builder =>
+            {
+                builder.AddOpenTelemetry(options =>
+                {
+                    options.AddInMemoryExporter(logRecords);
+                });
+                builder.AddFilter(typeof(LogsHelperTests).FullName, LogLevel.Trace);
+            });
+
+            var categoryName = nameof(LogsHelperTests);
+            var logger = loggerFactory.CreateLogger(categoryName);
+
+            logger.LogInformation("Information goes here");
+
+            var properties = new ChangeTrackingDictionary<string, string>();
+            LogsHelper.GetMessageAndSetProperties(logRecords[0], properties);
+
+            Assert.True(properties.TryGetValue("CategoryName", out string loggedCategoryName));
+            Assert.Equal(categoryName, loggedCategoryName);
+            Assert.Single(properties);
+        }
+
+        [Fact]
+        public void ExceptionPropertiesContainLoggerCategoryName()
+        {
+            var logRecords = new List<LogRecord>();
+            using var loggerFactory = LoggerFactory.Create(builder =>
+            {
+                builder.AddOpenTelemetry(options =>
+                {
+                    options.AddInMemoryExporter(logRecords);
+                });
+                builder.AddFilter(typeof(LogsHelperTests).FullName, LogLevel.Trace);
+            });
+
+            var logger = loggerFactory.CreateLogger<LogsHelperTests>();
+            try
+            {
+                throw new Exception("Test Exception");
+            }
+            catch (Exception ex)
+            {
+                logger.LogError(ex, "Here's an error");
+            }
+
+            var properties = new ChangeTrackingDictionary<string, string>();
+            var message = LogsHelper.GetMessageAndSetProperties(logRecords[0], properties);
+
+            Assert.Equal("Test Exception", message);
+
+            Assert.True(properties.TryGetValue("CategoryName", out string categoryName));
+            Assert.EndsWith(nameof(LogsHelperTests), categoryName);
         }
 
         [Fact]
@@ -318,13 +376,13 @@ public void VerifyHandlingOfVariousScopeDataTypes(object scopeValue)
 
             if (scopeValue != null)
             {
-                Assert.Single(properties); // Assert that there is exactly one property
+                Assert.Equal(2, properties.Count); // Scope property + CategoryName
                 Assert.True(properties.TryGetValue(expectedScopeKey, out string actualScopeValue));
                 Assert.Equal(scopeValue.ToString(), actualScopeValue);
             }
             else
             {
-                Assert.Empty(properties); // Assert that properties are empty
+                Assert.Single(properties); // Single property expected (CategoryName)
             }
         }
 
@@ -408,7 +466,7 @@ public void DuplicateKeysInLogRecordAttributesAndLogScope()
             var properties = new ChangeTrackingDictionary<string, string>();
             LogsHelper.GetMessageAndSetProperties(logRecords[0], properties);
 
-            Assert.Equal(2, properties.Count);
+            Assert.Equal(3, properties.Count);
             Assert.True(properties.TryGetValue(expectedScopeKey, out string actualScopeValue));
             Assert.Equal(expectedScopeValue, actualScopeValue);
             Assert.True(properties.TryGetValue("attributeKey", out string actualAttributeValue));

sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/tests/Azure.Monitor.OpenTelemetry.Exporter.Tests/MessageDataTests.cs

@@ -41,7 +41,7 @@ public void ValidateMessageData(LogLevel logLevel)
 
             Assert.Equal("Log Message", messageData.Message);
             Assert.Equal(LogsHelper.GetSeverityLevel(logLevel), messageData.SeverityLevel);
-            Assert.Empty(messageData.Properties);
+            Assert.Single(messageData.Properties); // CategoryName property expected
             Assert.Empty(messageData.Measurements);
         }
     }