Milestone 3

backend/app/core/logging.py

@@ -0,0 +1,34 @@
+"""JSON structured logging on stdout."""
+
+from __future__ import annotations
+
+import logging
+import sys
+
+from pythonjsonlogger import jsonlogger
+
+
+def configure_logging(level: str = "INFO") -> None:
+    """Replace the root handler with a single JSON stdout handler.
+
+    Fields emitted: ts, level, name, msg, plus any extras passed via `logger.X(..., extra={...})`.
+    """
+    root = logging.getLogger()
+    root.setLevel(level.upper())
+
+    # Drop any pre-existing handlers (uvicorn/gunicorn add their own).
+    for h in list(root.handlers):
+        root.removeHandler(h)
+
+    handler = logging.StreamHandler(sys.stdout)
+    formatter = jsonlogger.JsonFormatter(
+        fmt="%(asctime)s %(levelname)s %(name)s %(message)s",
+        rename_fields={"asctime": "ts", "levelname": "level", "name": "logger"},
+        json_ensure_ascii=False,
+    )
+    handler.setFormatter(formatter)
+    root.addHandler(handler)
+
+    # Tame the noisy third parties unless explicitly debugging.
+    if level.upper() != "DEBUG":
+        logging.getLogger("werkzeug").setLevel(logging.WARNING)