LogLayer

loglayer is a unified logger that routes logs to various logging libraries, cloud providers, files, and OpenTelemetry while providing a fluent API for specifying log messages, metadata and errors.

Supports browser, Node.js, Bun, and Deno platforms.

For full documentation, read the docs.

// Example using the Pino logging library with LogLayer
// You can also start out with a console logger and swap to another later!
import { LogLayer } from 'loglayer';
import { pino } from 'pino';
import { PinoTransport } from '@loglayer/transport-pino';
import { redactionPlugin } from '@loglayer/plugin-redaction';

const log = new LogLayer({
  // Multiple loggers can also be used at the same time. 
  transport: new PinoTransport({
    logger: pino()
  }),
  // Plugins modify log data before it's shipped to your logging library.
  plugins: [
    redactionPlugin({
      paths: ['password'],
      censor: '[REDACTED]',
    }),
  ],
  // Put context data in a specific field (default is flattened)
  contextFieldName: 'context',
  // Put metadata in a specific field (default is flattened)
  metadataFieldName: 'metadata',
})

// persisted data that is always included in logs
log.withContext({
   path: "/",
   reqId: "1234"
})

log.withPrefix("[my-app]")
  .withError(new Error('test'))
  // data that is included for this log entry only
  .withMetadata({ some: 'data', password: 'my-pass' })
  // Non-object data only (numbers, booleans, and strings only)
  // this can be omitted to just log an object / error
  // by using .errorOnly() / .metadataOnly() instead of withError() / withMetadata()
  .info('my message')

{
   "level": 30,
   "time": 1735857465669,
   "msg": "[my-app] my message",
   "context": {
      "path": "/",
      "reqId": "1234",
   },
   "metadata": {
      "password": "[REDACTED]",
      "some": "data",
   },
   "err":{
      "type": "Error",
      "message": "test",
      "stack": "Error: test\n ..."
   }
}

With the Pretty Terminal Transport:

The Hot Shots Mixin adds a metrics API to LogLayer:

import { LogLayer, useLogLayerMixin, ConsoleTransport } from 'loglayer';
import { StatsD } from 'hot-shots';
import { hotshotsMixin } from '@loglayer/mixin-hot-shots';

// Create a StatsD client
const statsd = new StatsD({
  host: 'localhost',
  port: 8125
});

// Register the mixin (must be called before creating LogLayer instances)
useLogLayerMixin(hotshotsMixin(statsd));

// Create LogLayer instance
const log = new LogLayer({
  transport: new ConsoleTransport({
    logger: console
  })
});

// Use StatsD methods through the stats property
log.stats.increment('request.count').send();
log.info('Request received');
log.stats.timing('request.duration', 150).send();
log.info('Request processed');
log.stats.gauge('active.connections', 42).send();
log.info('Connection established');

Development Setup

This is a monorepo using pnpm for package management and turbo for build orchestration. If you're looking to contribute or work with the source code, follow these steps:

1. Clone the repository
2. Install dependencies:

   pnpm install

3. Install git hooks:

   pnpx lefthook install

4. Build all packages:

   turbo build

Running Tests

To run tests for all packages, use the following command:

turbo test

Linting and Formatting

This project uses Biome for linting and formatting. To run lint and format across all packages:

turbo lint

To run lint only on staged files (used by git hooks):

turbo lint:staged

Viewing docs

The docs use vitepress. To view the docs locally, run:

pnpm run docs

To check that docs build correctly and are ready for production:

pnpm run docs:build

Project Structure

loglayer/
├── docs/                         # Documentation (vitepress)
├── packages/
│   ├── core/                     # Core packages
│   │   ├── context-manager/      # Context manager system core
│   │   ├── log-level-manager/    # Log level manager system core
│   │   ├── loglayer/             # Main LogLayer implementation
│   │   ├── plugin/               # Plugin system core
│   │   ├── transport/            # Transport system core
│   │   ├── shared/               # Shared utilities and types
│   │   └── tsconfig/             # Shared TypeScript configurations
│   ├── context-managers/         # Official context manager implementations
│   ├── log-level-managers/       # Official log level manager implementations
│   ├── transports/               # Official transport implementations
│   ├── mixins/                   # Official mixins implementations
│   ├── plugins/                  # Official plugins
│   └── integrations/             # Framework integrations (e.g. ElysiaJS)

Documentation

For detailed documentation, visit https://loglayer.dev

Contributing

We welcome contributions! Please see our Contributing Guide for details.

Made with ❤️ by Theo Gravity. Logo by Akshaya Madhavan.