Fix bug where 'gen_ai.response.finish_reasons' was not being correctly populated.

Author: michaelsafyan

instrumentation-genai/opentelemetry-instrumentation-google-genai/src/opentelemetry/instrumentation/google_genai/generate_content.py

@@ -252,6 +252,7 @@ def process_response(self, response: GenerateContentResponse):
         # need to be reflected back into the span attributes.
         #
         # See also: TODOS.md.
+        self._update_finish_reasons(response)
         self._maybe_update_token_counts(response)
         self._maybe_update_error_type(response)
         self._maybe_log_response(response)
@@ -275,6 +276,16 @@ def finalize_processing(self):
         self._record_token_usage_metric()
         self._record_duration_metric()
 
+    def _update_finish_reasons(self, response):
+        if not response.candidates:
+            return
+        for candidate in response.candidates:
+            finish_reason = candidate.finish_reason
+            if finish_reason is None:
+                continue
+            finish_reason_str = finish_reason.name.lower().removeprefix('finish_reason_')
+            self._finish_reasons_set.add(finish_reason_str)
+
     def _maybe_update_token_counts(self, response: GenerateContentResponse):
         input_tokens = _get_response_property(
             response, "usage_metadata.prompt_token_count"

instrumentation-genai/opentelemetry-instrumentation-google-genai/tests/generate_content/test_finish_reasons.py

@@ -0,0 +1,103 @@
+# Copyright The OpenTelemetry Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import unittest
+
+from google.genai import types as genai_types
+from .base import TestCase
+
+class FinishReasonsTestCase(TestCase):
+
+    def generate_and_get_span_finish_reasons(self):
+        self.client.models.generate_content(
+            model='gemini-2.5-flash-001',
+            contents='Some prompt')
+        span = self.otel.get_span_named("generate_content gemini-2.5-flash-001")
+        assert span is not None
+        assert "gen_ai.response.finish_reasons" in span.attributes
+        return list(span.attributes["gen_ai.response.finish_reasons"])
+
+    def test_single_candidate_with_valid_reason(self):
+        self.configure_valid_response(candidate=genai_types.Candidate(
+            finish_reason=genai_types.FinishReason.STOP
+        ))
+        self.assertEqual(
+            self.generate_and_get_span_finish_reasons(),
+            ["stop"])
+
+    def test_single_candidate_with_safety_reason(self):
+        self.configure_valid_response(candidate=genai_types.Candidate(
+            finish_reason=genai_types.FinishReason.SAFETY
+        ))
+        self.assertEqual(
+            self.generate_and_get_span_finish_reasons(),
+            ["safety"])
+
+    def test_single_candidate_with_max_tokens_reason(self):
+        self.configure_valid_response(candidate=genai_types.Candidate(
+            finish_reason=genai_types.FinishReason.MAX_TOKENS
+        ))
+        self.assertEqual(
+            self.generate_and_get_span_finish_reasons(),
+            ["max_tokens"])
+
+    def test_single_candidate_with_no_reason(self):
+        self.configure_valid_response(candidate=genai_types.Candidate(
+            finish_reason=None
+        ))
+        self.assertEqual(
+            self.generate_and_get_span_finish_reasons(),
+            [])
+
+    def test_single_candidate_with_unspecified_reason(self):
+        self.configure_valid_response(candidate=genai_types.Candidate(
+            finish_reason=genai_types.FinishReason.FINISH_REASON_UNSPECIFIED
+        ))
+        self.assertEqual(
+            self.generate_and_get_span_finish_reasons(),
+            ["unspecified"])
+
+    def test_multiple_candidates_with_valid_reasons(self):
+        self.configure_valid_response(candidates=[
+            genai_types.Candidate(finish_reason=genai_types.FinishReason.MAX_TOKENS),
+            genai_types.Candidate(finish_reason=genai_types.FinishReason.STOP),
+        ])
+        self.assertEqual(
+            self.generate_and_get_span_finish_reasons(),
+            ["max_tokens", "stop"])
+
+    def test_sorts_finish_reasons(self):
+        self.configure_valid_response(candidates=[
+            genai_types.Candidate(finish_reason=genai_types.FinishReason.STOP),
+            genai_types.Candidate(finish_reason=genai_types.FinishReason.MAX_TOKENS),
+            genai_types.Candidate(finish_reason=genai_types.FinishReason.SAFETY),
+        ])
+        self.assertEqual(
+            self.generate_and_get_span_finish_reasons(),
+            ["max_tokens", "safety", "stop"])
+
+    def test_deduplicates_finish_reasons(self):
+        self.configure_valid_response(candidates=[
+            genai_types.Candidate(finish_reason=genai_types.FinishReason.STOP),
+            genai_types.Candidate(finish_reason=genai_types.FinishReason.MAX_TOKENS),
+            genai_types.Candidate(finish_reason=genai_types.FinishReason.STOP),
+            genai_types.Candidate(finish_reason=genai_types.FinishReason.STOP),
+            genai_types.Candidate(finish_reason=genai_types.FinishReason.SAFETY),
+            genai_types.Candidate(finish_reason=genai_types.FinishReason.STOP),
+            genai_types.Candidate(finish_reason=genai_types.FinishReason.STOP),
+            genai_types.Candidate(finish_reason=genai_types.FinishReason.STOP),
+        ])
+        self.assertEqual(
+            self.generate_and_get_span_finish_reasons(),
+            ["max_tokens", "safety", "stop"])