feat: log exceptions for the logging hook

Signed-off-by: Lukas Reining <[email protected]>

Author: lukas-reining

libs/hooks/open-telemetry/src/lib/otel-hook.ts

@@ -37,7 +37,7 @@ export type OpenTelemetryHookOptions = {
    * will not be recorded on the active span.
    * By default, exceptions are recorded on the active span, if there is one.
    */
-  excludeExceptionsFromTrace?: boolean;
+  excludeExceptions?: boolean;
 
   /**
    * Takes a telemetry event and returns a telemetry event.
@@ -54,7 +54,7 @@ export abstract class OpenTelemetryHook {
   protected abstract name: string;
 
   protected attributesToExclude: TelemetryAttributesNames[];
-  protected excludeExceptionsFromTrace: boolean;
+  protected excludeExceptions: boolean;
   protected safeAttributeMapper: AttributeMapper;
   protected safeEventMutator: EventMutator;
 
@@ -76,7 +76,7 @@ export abstract class OpenTelemetryHook {
       }
     };
     this.attributesToExclude = options?.excludeAttributes ?? [];
-    this.excludeExceptionsFromTrace = options?.excludeExceptionsFromTrace ?? false;
+    this.excludeExceptions = options?.excludeExceptions ?? false;
   }
 
   protected toEvaluationEvent(

libs/hooks/open-telemetry/src/lib/traces/tracing-hook.ts

@@ -1,8 +1,13 @@
 import type { BaseHook, HookContext, EvaluationDetails, FlagValue, Logger } from '@openfeature/core';
-import type { Span } from '@opentelemetry/api';
+import type { Attributes, Exception, Span } from '@opentelemetry/api';
 import { trace } from '@opentelemetry/api';
-import type { EventLogger } from '@opentelemetry/api-events';
+import type { EventLogger, Event } from '@opentelemetry/api-events';
 import { events } from '@opentelemetry/api-events';
+import {
+  ATTR_EXCEPTION_MESSAGE,
+  ATTR_EXCEPTION_STACKTRACE,
+  ATTR_EXCEPTION_TYPE,
+} from '@opentelemetry/semantic-conventions';
 import type { OpenTelemetryHookOptions } from '../otel-hook';
 import { OpenTelemetryHook } from '../otel-hook';
 
@@ -27,10 +32,41 @@ export class EventHook extends OpenTelemetryHook implements BaseHook {
   }
 
   error(_: HookContext, err: Error) {
-    if (!this.excludeExceptionsFromTrace) {
-      trace.getActiveSpan()?.recordException(err);
+    if (!this.excludeExceptions) {
+      this.eventLogger.emit(this.toExceptionLogEvent(err));
     }
   }
+
+  /**
+   * Converts an exception to an OpenTelemetry log event.
+   * The event is compatible to https://opentelemetry.io/docs/specs/semconv/exceptions/exceptions-logs/
+   * The mapping code is adapted from the OpenTelemetry JS SDK:
+   * https://github.com/open-telemetry/opentelemetry-js/blob/09bf31eb966bab627e76a6c5c05c6e51ccd2f387/packages/opentelemetry-sdk-trace-base/src/Span.ts#L330
+   * @private
+   */
+  private toExceptionLogEvent(exception: Exception): Event {
+    const attributes: Attributes = {};
+    if (typeof exception === 'string') {
+      attributes[ATTR_EXCEPTION_MESSAGE] = exception;
+    } else if (exception) {
+      if (exception.code) {
+        attributes[ATTR_EXCEPTION_TYPE] = exception.code.toString();
+      } else if (exception.name) {
+        attributes[ATTR_EXCEPTION_TYPE] = exception.name;
+      }
+      if (exception.message) {
+        attributes[ATTR_EXCEPTION_MESSAGE] = exception.message;
+      }
+      if (exception.stack) {
+        attributes[ATTR_EXCEPTION_STACKTRACE] = exception.stack;
+      }
+    }
+
+    return {
+      name: 'exception',
+      attributes,
+    };
+  }
 }
 
 /**
@@ -58,7 +94,7 @@ export class SpanEventHook extends OpenTelemetryHook implements BaseHook {
   }
 
   error(_: HookContext, err: Error) {
-    if (!this.excludeExceptionsFromTrace) {
+    if (!this.excludeExceptions) {
       trace.getActiveSpan()?.recordException(err);
     }
   }
@@ -105,7 +141,7 @@ export class SpanHook extends OpenTelemetryHook implements BaseHook {
   }
 
   error(hookContext: Readonly<HookContext<FlagValue, SpanAttributesTracingHookData>>, err: Error) {
-    if (!this.excludeExceptionsFromTrace) {
+    if (!this.excludeExceptions) {
       const currentSpan = hookContext.hookData.get(HookContextSpanKey) ?? trace.getActiveSpan();
       currentSpan?.recordException(err);
     }