fix: 渲染引擎flag解析增加调试日志 + 统一fallback行为

- 三个入口(compose_video/edit_plan/generate_video)都增加flag配置详情日志
  （enabled/percentage/whitelist/default_engine），灰度期间便于排查
- 统一fallback行为：异常时全部fallback到legacy（保守策略）
  之前generate_video异常时fallback到unified，与其他入口不一致

apps/worker/worker_app/tasks/compose_video.py

@@ -59,15 +59,30 @@ def compose_video(self, job_id: str, **kwargs):
         # 判断使用哪个渲染引擎
         # 优先级：Redis Feature Flag（白名单 > 百分比） > 环境变量默认
         from video_processing.render_engine_resolver import get_render_engine_resolver
+        from video_processing.render_metrics import render_task_metrics
 
         resolver = get_render_engine_resolver()
         user_id = job.created_by_user_id or None
         engine = resolver.get_engine(user_id=user_id)
+        # 灰度期间打印详细 flag 配置，便于排查
+        config = resolver.get_config_snapshot()
+        logger.info(
+            "compose_video 引擎选择: job_id=%s engine=%s user_id=%s enabled=%s percentage=%s whitelist=%d default=%s",
+            job_id,
+            engine,
+            user_id,
+            config.get("enabled"),
+            config.get("percentage"),
+            len(config.get("whitelist", [])),
+            config.get("default_engine"),
+        )
 
-        if engine == "unified":
-            return _compose_with_unified_engine(self, job_service, job, plan_id, db)
-        else:
-            return _compose_with_legacy_engine(self, job_service, job, plan_id, db)
+        # 灰度观测指标埋点
+        with render_task_metrics(engine=engine, task_type="compose_video"):
+            if engine == "unified":
+                return _compose_with_unified_engine(self, job_service, job, plan_id, db)
+            else:
+                return _compose_with_legacy_engine(self, job_service, job, plan_id, db)
 
     except self.retry_exc as exc:
         logger.warning("视频合成重试中: job_id=%s, exc=%s", job_id, exc)

apps/worker/worker_app/tasks/edit_plan_generation.py

@@ -77,9 +77,21 @@ def _resolve_render_engine(user_id: str) -> str:
         from video_processing.render_engine_resolver import get_render_engine_resolver
 
         resolver = get_render_engine_resolver()
-        return resolver.get_engine(user_id=user_id)
+        engine = resolver.get_engine(user_id=user_id)
+        # 灰度期间打印详细 flag 配置，便于排查
+        config = resolver.get_config_snapshot()
+        logger.info(
+            "edit_plan 引擎选择: user_id=%s engine=%s enabled=%s percentage=%s whitelist=%d default=%s",
+            user_id,
+            engine,
+            config.get("enabled"),
+            config.get("percentage"),
+            len(config.get("whitelist", [])),
+            config.get("default_engine"),
+        )
+        return engine
     except Exception as exc:
-        logger.warning("获取渲染引擎配置失败，fallback 到 legacy: %s", exc)
+        logger.warning("获取渲染引擎配置失败，fallback 到 legacy: %s", exc, exc_info=True)
         return "legacy"
 
 

apps/worker/worker_app/tasks/generation.py

@@ -787,10 +787,23 @@ def _resolve_render_engine(user_id: str) -> str:
         from video_processing.render_engine_resolver import get_render_engine_resolver
 
         resolver = get_render_engine_resolver()
-        return resolver.get_engine(user_id=user_id)
+        engine = resolver.get_engine(user_id=user_id)
+        # 灰度期间打印详细 flag 配置，便于排查
+        config = resolver.get_config_snapshot()
+        logger.info(
+            "[渲染引擎] flag 解析: user_id=%s engine=%s enabled=%s percentage=%s whitelist=%d default=%s",
+            user_id,
+            engine,
+            config.get("enabled"),
+            config.get("percentage"),
+            len(config.get("whitelist", [])),
+            config.get("default_engine"),
+        )
+        return engine
     except Exception as exc:
-        logger.warning("获取渲染引擎配置失败，fallback 到 unified: %s", exc)
-        return ENGINE_UNIFIED
+        # 异常时 fallback 到 legacy（保守策略，与 edit_plan_generation 一致）
+        logger.warning("获取渲染引擎配置失败，fallback 到 legacy: %s", exc, exc_info=True)
+        return ENGINE_LEGACY
 
 
 # ── 旧引擎渲染（FFmpeg filter_complex） ────────────────────────────────────────