Fable Log Logger Bunyan

A Bunyan log provider for fable-log. Outputs structured JSON logs through the standard fable logging interface, supporting all six log levels and custom stream configurations.

Features

• Structured JSON Logging - All log output is Bunyan-format JSON with timestamps, level numbers, hostnames, and PIDs
• Fable Log Provider - Extends the fable-log LogProviderBase, plugging directly into the fable logging pipeline
• Six Log Levels - trace, debug, info, warn, error, and fatal mapped to their Bunyan equivalents
• Object Context - Attach arbitrary data objects to any log call; they are merged into the JSON output
• Custom Streams - Pass Bunyan stream configurations (stdout, files, rotating files, ringbuffers) through the settings object
• Datum Decorators - Works with fable-log's setDatumDecorator to enrich log objects with application metadata

Installation

npm install fable-log-logger-bunyan

Quick Start

const libFable = require('fable');
const libFableLoggerBunyan = require('fable-log-logger-bunyan');

let fable = new libFable(
{
	Product: 'my-app',
	Version: '1.0.0',
	LogStreams: []
});

// Create the bunyan logger — settings are passed directly to Bunyan
let bunyanLogger = new libFableLoggerBunyan(
{
	name: fable.settings.Product
});

// Add it to the fable logging pipeline
fable.Logging.addLogger(bunyanLogger, 'trace');

// Log away
fable.log.info('Application started.');
fable.log.info('User loaded:', { id: 42, name: 'Ada' });
fable.log.error('Something went wrong!');

Usage

Custom Streams

Bunyan stream configurations are passed directly through the settings object:

const { PassThrough } = require('stream');
const logCapture = new PassThrough();

let bunyanLogger = new libFableLoggerBunyan(
{
	name: 'my-app',
	streams:
	[
		{ level: 'trace', stream: process.stdout },
		{ level: 'info', stream: logCapture },
		{ level: 'error', path: '/var/log/my-app-error.log' }
	]
});

fable.Logging.addLogger(bunyanLogger, 'trace');

Datum Decorators

Use fable-log's datum decorator to enrich every log entry with application context:

fable.log.setDatumDecorator((pSourceDatum) =>
{
	return {
		Source: fable.settings.Product,
		Meta: pSourceDatum
	};
});

fable.log.info('Hello!', { requestId: 'abc-123' });
// JSON output includes Source, Meta.requestId, msg, level, time, etc.

API

Constructor

new BunyanLogger(pLogStreamSettings, pLogStreamHash)

| Parameter | Type | Description | |-----------|------|-------------| | pLogStreamSettings | Object | Settings passed directly to bunyan.createLogger() (must include name) | | pLogStreamHash | String | Optional hash identifier for the log stream |

Log Methods

All methods accept a log message string and an optional context object:

| Method | Bunyan Level | Description | |--------|-------------|-------------| | trace(pLogText, pLogObject) | 10 | Finest-grain debug output | | debug(pLogText, pLogObject) | 20 | Debug-level messages | | info(pLogText, pLogObject) | 30 | Informational messages | | warn(pLogText, pLogObject) | 40 | Warning conditions | | error(pLogText, pLogObject) | 50 | Error conditions | | fatal(pLogText, pLogObject) | 60 | Fatal / unrecoverable errors |

Properties

| Property | Type | Description | |----------|------|-------------| | bunyanLogger | Object | The underlying Bunyan logger instance |

Part of the Retold Framework

Fable Log Logger Bunyan is a logging provider in the Fable ecosystem:

• fable-log - Logging framework with pluggable providers
• fable - Application services framework
• fable-serviceproviderbase - Service provider base class

Testing

Run the test suite:

npm test

Run with coverage:

npm run coverage

Related Packages

• fable - Application services framework
• fable-log - Logging services

License

MIT

Contributing

Pull requests are welcome. For details on our code of conduct, contribution process, and testing requirements, see the Retold Contributing Guide.