loglayer

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loglayer is a unified Typescript 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.

``javascript
// 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')
`

`json5
{
"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:

!Pretty Terminal Transport

The Hot Shots Mixin adds a metrics API to LogLayer:

`typescript
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');
`

Installation

Install the core package:

`bash
npm i loglayer
`

Quick Start

`typescript
import { LogLayer, ConsoleTransport } from 'loglayer'

const log = new LogLayer({
transport: new ConsoleTransport({
logger: console,
}),
})

log
.withMetadata({ some: 'data'})
.withError(new Error('test'))
.info('my message')
``

- See the LogLayer configuration documentation for more configuration options.
- See the Console Transport documentation for more configuration options.