chore: add structured logging with structlog; add request_id middleware; replace std logging

app/logging_config.py

@@ -0,0 +1,57 @@
+"""
+Structured logging configuration for the Delphi Database FastAPI app.
+
+This module configures structlog to output JSON logs and integrates
+context variables so request-specific fields (e.g., request_id) are
+included automatically in log records.
+"""
+
+from __future__ import annotations
+
+import logging
+from typing import Any, Dict
+
+import structlog
+
+
+def _add_required_defaults(_: Any, __: str, event_dict: Dict[str, Any]) -> Dict[str, Any]:
+    """
+    Ensure all required fields exist on every log entry so downstream
+    consumers receive a consistent schema.
+    """
+    # Required fields per project requirements
+    event_dict.setdefault("request_id", None)
+    event_dict.setdefault("http.method", None)
+    event_dict.setdefault("http.path", None)
+    event_dict.setdefault("status_code", None)
+    event_dict.setdefault("user.id", None)
+    event_dict.setdefault("duration_ms", None)
+    return event_dict
+
+
+def setup_logging(log_level: int = logging.INFO) -> None:
+    """
+    Configure structlog for JSON logging with contextvars support.
+
+    Args:
+        log_level: Minimum log level for application logs.
+    """
+    # Configure stdlib logging basic config for third-party libs (uvicorn, etc.)
+    logging.basicConfig(level=log_level)
+
+    structlog.configure(
+        processors=[
+            structlog.contextvars.merge_contextvars,
+            structlog.stdlib.add_log_level,
+            _add_required_defaults,
+            structlog.processors.TimeStamper(fmt="iso", key="timestamp"),
+            structlog.processors.dict_tracebacks,
+            structlog.processors.JSONRenderer(),
+        ],
+        context_class=dict,
+        logger_factory=structlog.stdlib.LoggerFactory(),
+        wrapper_class=structlog.make_filtering_bound_logger(log_level),
+        cache_logger_on_first_use=True,
+    )
+
+