Transports API

Transports deliver formatted logs to destinations.

Interface

interface Transport {
  log(entry: LogEntry, formatted: string): Promise<void> | void
}

Built-in Transports

consoleTransport

function consoleTransport(): Transport

Writes to stdout/stderr.

import { consoleTransport } from '@sylphx/cat'

const transport = consoleTransport()

fileTransport

function fileTransport(options: FileTransportOptions): Transport

Writes to a file.

interface FileTransportOptions {
  path: string // File path (required)
}

import { fileTransport } from '@sylphx/cat'

const transport = fileTransport({
  path: './logs/app.log'
})

streamTransport

function streamTransport(options: StreamTransportOptions): Transport

Writes to a writable stream.

interface StreamTransportOptions {
  stream: NodeJS.WritableStream // Writable stream (required)
}

import { streamTransport } from '@sylphx/cat'
import fs from 'node:fs'

const transport = streamTransport({
  stream: process.stdout
})

otlpTransport

function otlpTransport(options?: OtlpTransportOptions): Transport

Sends logs via OpenTelemetry Protocol.

interface OtlpTransportOptions {
  endpoint?: string // OTLP endpoint (default: http://localhost:4318/v1/logs)
  headers?: Record<string, string> // HTTP headers
  batch?: boolean // Enable batching (default: false)
  batchSize?: number // Batch size (default: 100)
  batchInterval?: number // Batch interval ms (default: 1000)
  compression?: 'gzip' | 'none' // Compression (default: 'none')
  retries?: number // Retry attempts (default: 3)
  timeout?: number // Request timeout ms (default: 5000)
  resourceAttributes?: Record<string, string> // Resource attributes
  scopeName?: string // Scope name
  scopeVersion?: string // Scope version
}

import { otlpTransport } from '@sylphx/cat'

const transport = otlpTransport({
  endpoint: 'http://localhost:4318/v1/logs',
  batch: true,
  resourceAttributes: {
    'service.name': 'my-api'
  }
})

Custom Transport

import type { Transport, LogEntry } from '@sylphx/cat'

class CustomTransport implements Transport {
  async log(entry: LogEntry, formatted: string): Promise<void> {
    await fetch('https://logs.example.com', {
      method: 'POST',
      body: formatted
    })
  }
}

const logger = createLogger({
  transports: [new CustomTransport()]
})

See Also

• Logger API
• Transports Guide
• OTLP Guide