feat: add 'log_structured_entry' for JSON structured logs

Move config into own file

utils/logging_setup.py

@@ -0,0 +1,50 @@
+"""
+Centralized Cloud Logging setup.
+Uses CloudLoggingHandler (background thread) so logging does not add latency
+"""
+
+import logging
+from typing import Optional, Dict, Literal
+
+import google.cloud.logging
+from google.cloud.logging.handlers import CloudLoggingHandler
+
+from .config import Settings
+
+
+def _setup_logger() -> logging.Logger:
+    """Create or return the singleton evaluation logger."""
+    log_name = "va_agent-evaluation-logs"
+    logger = logging.getLogger(log_name)
+    cfg = Settings.model_validate({})
+    if any(isinstance(h, CloudLoggingHandler) for h in logger.handlers):
+        return logger
+
+    try:
+        client = google.cloud.logging.Client(project=cfg.project_id)
+        handler = CloudLoggingHandler(client, name=log_name)  # async transport
+        logger.addHandler(handler)
+        logger.setLevel(logging.INFO)
+    except Exception as e:
+        # Fallback to console if Cloud Logging is unavailable (local dev)
+        logging.basicConfig(level=logging.INFO)
+        logger = logging.getLogger(log_name)
+        logger.warning("Cloud Logging setup failed; using console. Error: %s", e)
+
+    return logger
+
+
+_eval_log = _setup_logger()
+
+
+def log_structured_entry(message: str, severity: Literal["INFO", "WARNING", "ERROR"], custom_log: Optional[Dict] = None) -> None:
+    """
+    Emit a JSON-structured log row.
+
+    Args:
+        message: Short label for the row (e.g., "Final agent turn").
+        severity: "INFO" | "WARNING" | "ERROR" etc.
+        custom_log: A dict with your structured payload.
+    """
+    level = getattr(logging, severity.upper(), logging.INFO)
+    _eval_log.log(level, message, extra={"json_fields": {"message": message, "custom": custom_log or {}}})