fable-log-logger-bunyan

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.

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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.