Logging

The API uses structured JSON logging with request ID correlation, dual output (stdout + rotating file), and centralized dictConfig configuration.

Configuration

Logging is initialized at application startup in the FastAPI lifespan handler:

# src/qdash/api/db/session.py
from qdash.api.logging_config import setup_logging
setup_logging()

The log level is controlled by the LOG_LEVEL environment variable (default: INFO):

# In .env or docker compose environment
LOG_LEVEL=DEBUG

The configuration lives in src/qdash/api/logging_config.py and uses pythonjsonlogger for JSON formatting.

Suppressed Loggers

Third-party loggers are set to WARNING to reduce noise:

Logger	Level
uvicorn, uvicorn.access, uvicorn.error	WARNING
gunicorn, gunicorn.access, gunicorn.error	WARNING
pymongo, pymongo.command, pymongo.topology, pymongo.connection	WARNING

Log Format

Each log entry is a JSON object with the following fields:

Field	Description	Example
timestamp	ISO 8601 timestamp	"2025-12-21 10:30:45,123"
name	Logger name (module path)	"qdash.api.routers.chip"
level	Log level	"INFO"
message	Log message	"Chip data updated"
request_id	Correlation ID from middleware	"a1b2c3d4"

Example output:

{"timestamp": "2025-12-21 10:30:45,123", "name": "qdash.api.routers.chip", "level": "INFO", "message": "Chip data updated", "request_id": "a1b2c3d4"}

Request ID

The RequestIdMiddleware assigns a unique ID to every incoming HTTP request:

1. If the client sends an X-Request-ID header, that value is used
2. Otherwise, a short UUID (8 hex characters) is generated
3. The ID is stored in a ContextVar and injected into every log record by RequestIdFilter
4. The ID is echoed back in the X-Request-ID response header

This allows you to correlate all log entries produced during a single request:

# Filter logs for a specific request
jq 'select(.request_id == "a1b2c3d4")' logs/api/api.log

Adding Logging to New Modules

Use the standard logging.getLogger(__name__) pattern:

import logging

logger = logging.getLogger(__name__)

def some_function():
    logger.info("Processing started", extra={"item_id": "123"})
    # ...
    logger.warning("Unexpected value", extra={"value": value})

The request_id field is injected automatically by the logging filter. You do not need to add it manually.

Log File Access

In Docker, the API container writes logs to /app/logs/api.log, which is mounted to the host:

# compose.yaml
volumes:
  - ./logs/api:/app/logs

Setting	Value
Host path	./logs/api/api.log
Container path	/app/logs/api.log
Max file size	10 MB
Backup count	5
Rotation	RotatingFileHandler (automatic)

When the log file reaches 10 MB, it is rotated to api.log.1, api.log.2, etc., keeping up to 5 backups.

Filtering & Querying

Since logs are JSON, you can use jq to filter and query them:

# All errors
jq 'select(.level == "ERROR")' logs/api/api.log

# Logs from a specific module
jq 'select(.name == "qdash.api.routers.chip")' logs/api/api.log

# Logs for a specific request ID
jq 'select(.request_id == "a1b2c3d4")' logs/api/api.log

# Errors in the last hour (requires GNU date)
jq --arg since "$(date -d '1 hour ago' '+%Y-%m-%d %H:%M')" \
  'select(.level == "ERROR" and .timestamp >= $since)' logs/api/api.log

# Count log entries by level
jq -s 'group_by(.level) | map({level: .[0].level, count: length})' logs/api/api.log

For live log streaming:

# Stream console logs via docker compose
docker compose logs -f api

# Stream and filter the log file
tail -f logs/api/api.log | jq 'select(.level == "ERROR")'

Implementation Files

• src/qdash/api/logging_config.py — centralized setup_logging()
• src/qdash/api/middleware/request_id.py — request ID middleware and filter
• src/qdash/api/main.py — middleware registration
• src/qdash/api/db/session.py — lifespan handler calling setup_logging()