dis-infra-python-logging

ONS Dissemination JSON log formatter for Python Lambda functions.

Implements the ONS logging standards as a reusable package.

Installation

pip install dis-logging

Or with Poetry:

[tool.poetry.dependencies]
dis-logging = "^1.0.0"

Usage

Call configure_logging() once in your handler file:

from dis_logging import configure_logging

configure_logging()

That's it. All loggers in your code will output structured JSON. No arguments required — it reads configuration from environment variables.

How it works

• Configures the root logger with the ONS JSON format
• Every logging.getLogger(__name__) in your code inherits the formatter
• Third-party libraries (boto3, urllib3) are automatically covered
• If APP_LOG_LEVEL is set, your app code gets a separate log level while third-party libraries stay at the root level — so you can DEBUG your code without drowning in boto noise

Example

# my_module/handler.py
import logging
from dis_logging import configure_logging

configure_logging()
logger = logging.getLogger(__name__)

def lambda_handler(event, context):
    logger.info("Processing event", extra={"event_id": event.get("id")})
    return {"statusCode": 200}

Output:

{"created_at": "2024-01-15T10:30:00", "namespace": "my_module.handler", "severity": 3, "event": "Processing event", "data": {"event_id": "abc123"}}

Configuration

Environment variable	Description	Default
LOG_LEVEL	Root logger level (all loggers)	INFO
APP_LOG_LEVEL	Your app code's log level (auto-detected from caller package)	—

Severity levels

Level	Severity
CRITICAL	0
ERROR	1
WARNING	2
INFO	3
DEBUG	4

Development

make install  # Install dependencies
make test     # Run tests
make lint     # Run linting
make format   # Auto-format
make all      # Run everything

Releasing

Releases are automated. To create a new release:

1. Bump the version in pyproject.toml as part of your PR
2. Merge to main
3. The release workflow automatically creates a GitHub Release and tag

Contributing

Full contributing guidelines are covered here.

Licence

MIT