feat: Add status.message and exception.type attributes to OpenTelemetry spans

Added recursive logic to trace the final underlying exception message and updated relevant telemetry tests to test iteration logic as requested by client.

Author: diegomarquezp

gax-java/gax/src/main/java/com/google/api/gax/tracing/ObservabilityAttributes.java

@@ -79,4 +79,10 @@ public class ObservabilityAttributes {
    * Code, Client-Side Network/Operational Error (e.g., CLIENT_TIMEOUT) or internal fallback.
    */
   public static final String ERROR_TYPE_ATTRIBUTE = "error.type";
+
+  /** A human-readable error message, which may include details from the exception or response. */
+  public static final String STATUS_MESSAGE_ATTRIBUTE = "status.message";
+
+  /** If the error was caused by an exception, the exception class name. */
+  public static final String EXCEPTION_TYPE_ATTRIBUTE = "exception.type";
 }

gax-java/gax/src/main/java/com/google/api/gax/tracing/SpanTracer.java

@@ -109,10 +109,33 @@ private void recordErrorAndEndAttempt(Throwable error) {
     if (attemptHandle != null) {
       attemptHandle.addAttribute(
           ObservabilityAttributes.ERROR_TYPE_ATTRIBUTE, ObservabilityUtils.extractErrorType(error));
+
+      if (error != null) {
+        attemptHandle.addAttribute(
+            ObservabilityAttributes.EXCEPTION_TYPE_ATTRIBUTE, error.getClass().getName());
+
+        String errorMessage = extractErrorMessage(error);
+        if (errorMessage != null) {
+          attemptHandle.addAttribute(
+              ObservabilityAttributes.STATUS_MESSAGE_ATTRIBUTE, errorMessage);
+        }
+      }
+
       endAttempt();
     }
   }
 
+  private String extractErrorMessage(Throwable error) {
+    Throwable cause = error;
+    while (cause != null) {
+      if (cause.getMessage() != null && !cause.getMessage().isEmpty()) {
+        return cause.getMessage();
+      }
+      cause = cause.getCause();
+    }
+    return null;
+  }
+
   private void endAttempt() {
     if (attemptHandle != null) {
       attemptHandle.end();

gax-java/gax/src/test/java/com/google/api/gax/tracing/SpanTracerTest.java

@@ -297,6 +297,39 @@ void testAttemptFailed_internalFallback_nullError() {
     verify(attemptHandle).end();
   }
 
+  @Test
+  void testAttemptFailed_populatesExceptionTypeAndMessage() {
+    when(recorder.createSpan(eq(ATTEMPT_SPAN_NAME), anyMap())).thenReturn(attemptHandle);
+    tracer.attemptStarted(new Object(), 1);
+
+    tracer.attemptFailedRetriesExhausted(new IllegalStateException("custom error message"));
+
+    verify(attemptHandle)
+        .addAttribute(
+            ObservabilityAttributes.EXCEPTION_TYPE_ATTRIBUTE, "java.lang.IllegalStateException");
+    verify(attemptHandle)
+        .addAttribute(ObservabilityAttributes.STATUS_MESSAGE_ATTRIBUTE, "custom error message");
+    verify(attemptHandle).end();
+  }
+
+  @Test
+  void testAttemptFailed_recursiveMessageSearch() {
+    when(recorder.createSpan(eq(ATTEMPT_SPAN_NAME), anyMap())).thenReturn(attemptHandle);
+    tracer.attemptStarted(new Object(), 1);
+
+    Throwable cause = new IllegalArgumentException("root cause message");
+    Throwable wrapper = new IllegalStateException("", cause);
+
+    tracer.attemptFailedRetriesExhausted(wrapper);
+
+    verify(attemptHandle)
+        .addAttribute(
+            ObservabilityAttributes.EXCEPTION_TYPE_ATTRIBUTE, "java.lang.IllegalStateException");
+    verify(attemptHandle)
+        .addAttribute(ObservabilityAttributes.STATUS_MESSAGE_ATTRIBUTE, "root cause message");
+    verify(attemptHandle).end();
+  }
+
   private static class RedirectException extends RuntimeException {
     public RedirectException(String message) {
       super(message);

java-showcase/gapic-showcase/src/test/java/com/google/showcase/v1beta1/it/ITOtelErrorType.java

@@ -395,6 +395,23 @@ void testTracing_clientRequestError_IllegalArgumentException_grpc() throws Excep
     try (EchoClient client = createInterceptorClient(new IllegalArgumentException("Mock request error"))) {
       assertThrows(IllegalArgumentException.class, () -> client.echo(EchoRequest.newBuilder().setContent("test").build()));
       verifyErrorTypeAttribute("CLIENT_REQUEST_ERROR");
+      
+      SpanData errorSpan =
+          spanExporter.getFinishedSpanItems().stream()
+              .filter(span -> span.getAttributes().get(AttributeKey.stringKey(ObservabilityAttributes.ERROR_TYPE_ATTRIBUTE)) != null)
+              .findFirst()
+              .orElseThrow(() -> new AssertionError("Span with error.type not found"));
+
+      assertThat(
+              errorSpan
+                  .getAttributes()
+                  .get(AttributeKey.stringKey(ObservabilityAttributes.EXCEPTION_TYPE_ATTRIBUTE)))
+          .isEqualTo("java.lang.IllegalArgumentException");
+      assertThat(
+              errorSpan
+                  .getAttributes()
+                  .get(AttributeKey.stringKey(ObservabilityAttributes.STATUS_MESSAGE_ATTRIBUTE)))
+          .isEqualTo("Mock request error");
     }
   }