[Monitor OpenTelemetry Exporter] Add Support for Custom Events (#33183)

### Packages impacted by this PR
@azure/monitor-opentelemetry-exporter

### Describe the problem that is addressed by this PR
Adds support for custom events by setting the appropriate attribute on a
log record `"microsoft.custom_event.name"`.


### Are there test cases added in this PR? _(If not, why?)_
Yes, tests to ensure that log records created with the correct attribute
are sent as custom events.

### Checklists
- [x] Added impacted package name to the issue description
- [ ] Does this PR needs any fixes in the SDK Generator?** _(If so,
create an Issue in the
[Autorest/typescript](https://github.com/Azure/autorest.typescript)
repository and link it here)_
- [x] Added a changelog (if necessary)

Author: JacksonWeber

sdk/monitor/monitor-opentelemetry-exporter/CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Features Added
 
 - Support the AMW de-duping flag in AKS auto-attach scenarios.
+- Support sending custom events via specifying `microsoft.custom_event.name` on logs.
 - Support the stable OpenTelemetry HTTP semantic conventions.
 
 ### Other Changes

sdk/monitor/monitor-opentelemetry-exporter/src/utils/constants/applicationinsights.ts

@@ -33,6 +33,7 @@ export enum DependencyTypes {
 
 export const AzureMonitorSampleRate = "microsoft.sample_rate";
 export const ApplicationInsightsBaseType = "_MS.baseType";
+export const ApplicationInsightsCustomEventName = "microsoft.custom_event.name";
 
 export const ApplicationInsightsMessageName = "Microsoft.ApplicationInsights.Message";
 export const ApplicationInsightsExceptionName = "Microsoft.ApplicationInsights.Exception";

sdk/monitor/monitor-opentelemetry-exporter/src/utils/logUtils.ts

@@ -26,6 +26,7 @@ import {
   ApplicationInsightsAvailabilityBaseType,
   ApplicationInsightsAvailabilityName,
   ApplicationInsightsBaseType,
+  ApplicationInsightsCustomEventName,
   ApplicationInsightsEventBaseType,
   ApplicationInsightsEventName,
   ApplicationInsightsExceptionBaseType,
@@ -51,36 +52,47 @@ export function logToEnvelope(log: ReadableLogRecord, ikey: string): Envelope |
   let baseType: string;
   let baseData: MonitorDomain;
 
-  if (!log.attributes[ApplicationInsightsBaseType]) {
-    // Get Exception attributes if available
-    const exceptionType = log.attributes[ATTR_EXCEPTION_TYPE];
-    if (exceptionType) {
-      const exceptionMessage = log.attributes[ATTR_EXCEPTION_MESSAGE];
-      const exceptionStacktrace = log.attributes[ATTR_EXCEPTION_STACKTRACE];
-      name = ApplicationInsightsExceptionName;
-      baseType = ApplicationInsightsExceptionBaseType;
-      const exceptionDetails: TelemetryExceptionDetails = {
-        typeName: String(exceptionType),
-        message: String(exceptionMessage),
-        hasFullStack: exceptionStacktrace ? true : false,
-        stack: String(exceptionStacktrace),
-      };
-      const exceptionData: TelemetryExceptionData = {
-        exceptions: [exceptionDetails],
-        severityLevel: String(getSeverity(log.severityNumber)),
-        version: 2,
-      };
-      baseData = exceptionData;
-    } else {
-      name = ApplicationInsightsMessageName;
-      baseType = ApplicationInsightsMessageBaseType;
-      const messageData: MessageData = {
-        message: String(log.body),
-        severityLevel: String(getSeverity(log.severityNumber)),
-        version: 2,
-      };
-      baseData = messageData;
-    }
+  const exceptionStacktrace = log.attributes[ATTR_EXCEPTION_STACKTRACE];
+  const exceptionType = log.attributes[ATTR_EXCEPTION_TYPE];
+  const isExceptionType: boolean = !!(exceptionType && exceptionStacktrace) || false;
+  const isMessageType: boolean =
+    !log.attributes[ApplicationInsightsBaseType] &&
+    !log.attributes[ApplicationInsightsCustomEventName] &&
+    !exceptionType;
+  if (isExceptionType) {
+    const exceptionMessage = log.attributes[ATTR_EXCEPTION_MESSAGE];
+    name = ApplicationInsightsExceptionName;
+    baseType = ApplicationInsightsExceptionBaseType;
+    const exceptionDetails: TelemetryExceptionDetails = {
+      typeName: String(exceptionType),
+      message: String(exceptionMessage),
+      hasFullStack: exceptionStacktrace ? true : false,
+      stack: String(exceptionStacktrace),
+    };
+    const exceptionData: TelemetryExceptionData = {
+      exceptions: [exceptionDetails],
+      severityLevel: String(getSeverity(log.severityNumber)),
+      version: 2,
+    };
+    baseData = exceptionData;
+  } else if (log.attributes[ApplicationInsightsCustomEventName]) {
+    name = ApplicationInsightsEventName;
+    baseType = ApplicationInsightsEventBaseType;
+    const eventData: TelemetryEventData = {
+      name: String(log.attributes[ApplicationInsightsCustomEventName]),
+      version: 2,
+    };
+    baseData = eventData;
+    measurements = getLegacyApplicationInsightsMeasurements(log);
+  } else if (isMessageType) {
+    name = ApplicationInsightsMessageName;
+    baseType = ApplicationInsightsMessageBaseType;
+    const messageData: MessageData = {
+      message: String(log.body),
+      severityLevel: String(getSeverity(log.severityNumber)),
+      version: 2,
+    };
+    baseData = messageData;
   } else {
     // If Legacy Application Insights Log
     baseType = String(log.attributes[ApplicationInsightsBaseType]);
@@ -144,6 +156,7 @@ function createPropertiesFromLog(log: ReadableLogRecord): [Properties, Measureme
       if (
         !(
           key.startsWith("_MS.") ||
+          key.startsWith("microsoft") ||
           key === ATTR_EXCEPTION_TYPE ||
           key === ATTR_EXCEPTION_MESSAGE ||
           key === ATTR_EXCEPTION_STACKTRACE ||

sdk/monitor/monitor-opentelemetry-exporter/test/internal/logUtils.spec.ts

@@ -409,7 +409,7 @@ describe("logUtils.ts", () => {
       );
     });
 
-    it("should create a Event Envelope", () => {
+    it("should create an Event Envelope", () => {
       const data: TelemetryEventData = {
         name: "testName",
         version: 2,
@@ -444,6 +444,35 @@ describe("logUtils.ts", () => {
         expectedTime,
       );
     });
+
+    it("should create a Custom Event Envelope", () => {
+      testLogRecord.attributes = {
+        "microsoft.custom_event.name": "testing name",
+        "extra.attribute": "foo",
+      };
+      const expectedTime = hrTimeToDate(testLogRecord.hrTime);
+      const expectedProperties = {
+        "extra.attribute": "foo",
+      };
+      const expectedBaseData: TelemetryEventData = {
+        name: "testing name",
+        version: 2,
+        properties: expectedProperties,
+        measurements: {},
+      };
+
+      const envelope = logToEnvelope(testLogRecord as ReadableLogRecord, "ikey");
+      assertEnvelope(
+        envelope,
+        "Microsoft.ApplicationInsights.Event",
+        100,
+        "EventData",
+        expectedProperties,
+        emptyMeasurements,
+        expectedBaseData,
+        expectedTime,
+      );
+    });
   });
 
   it("should parse objects if passed as the message field of a legacy ApplicationInsights log", () => {