pino-tee

Tee pino logs into multiple files, according to the given levels.

Works with any newline delimited json stream.

Install

npm i pino-tee -g

Usage

CLI

Specify a minimum log level to write to file.

The following writes info, warn and error level logs to ./info-warn-error-log, and all output of app.js to ./all-logs:

node app.js | pino-tee info ./info-warn-error-logs | tee -a ./all-logs

(using tee -a ./all-logs will both write to ./all-logs and stdout, enabling piping of more pino transports)

Pino V7+

const pino = require('pino')

const pinoTee = pino.transport({
  target: 'pino-tee',
  options: {
    filters: {
      info: 'info.log',
      warn: 'warn.log'
    }
  }
})

const logger = pino(pinoTee)

logger.info('example info log')
logger.error('example error log')

NodeJS

You can log to multiple files by spawning a child process. In the following example pino-tee writes into three different files for warn, error & fatal log levels.

const pino = require('pino')
const childProcess = require('child_process')
const stream = require('stream')

// Environment variables
const cwd = process.cwd()
const { env } = process
const logPath = `${cwd}/log`

// Create a stream where the logs will be written
const logThrough = new stream.PassThrough()
const log = pino({ name: 'project' }, logThrough)

// Log to multiple files using a separate process
const child = childProcess.spawn(process.execPath, [
  require.resolve('pino-tee'),
  'warn', `${logPath}/warn.log`,
  'error', `${logPath}/error.log`,
  'fatal', `${logPath}/fatal.log`
], { cwd, env, stdio: ['pipe', 'inherit', 'inherit'] })

logThrough.pipe(child.stdin)

// Writing some test logs
log.warn('WARNING 1')
log.error('ERROR 1')
log.fatal('FATAL 1')

This prints raw logs into log files, you can also print pretty logs to the console for development purposes. For that, you need to use pino-multi-stream. See the example below

const pinoms = require('pino-multi-stream')
const childProcess = require('child_process')
const stream = require('stream')

const cwd = process.cwd()
const { env } = process

const logThrough = new stream.PassThrough()
const prettyStream = pinoms.prettyStream()
const streams = [
  { stream: logThrough },
  { stream: prettyStream }
]
const log = pinoms(pinoms.multistream(streams))

const child = childProcess.spawn(process.execPath, [
  require.resolve('pino-tee'),
  'warn', `${__dirname}/warn`,
  'error', `${__dirname}/error`,
  'fatal', `${__dirname}/fatal`
], { cwd, env })

logThrough.pipe(child.stdin)

// Writing some test logs
log.warn('WARNING 1')
log.error('ERROR 1')
log.fatal('FATAL 1')

Here, we're tapping into the write stream that pino-tee gets and manually formatting the log line using pino-pretty to write on the stdout. Note that the pretty printing is typically only done while developing.

API

pinoTee(source)

Create a new tee instance from source. It is an extended instance of cloneable-readable.

Example:

const { tee } = require('pino-tee')
const fs = require('fs')
const stream = tee(process.stdin)
stream.tee(fs.createWriteStream('errors'), line => line.level >= 50)
stream.pipe(process.stdout)

stream.tee(dest, [filter])

Create a new stream that will filter a given line based on some parameters. Each line is automatically parsed, or skipped if it is not a newline delimited json.

The filter can be a function with signature filter(line), where line  is a parsed JSON object. The filter can also be one of the pino levels either as text or as a custom level number, in that case all log lines with that level or greater will be written.

Acknowledgements

This project was kindly sponsored by nearForm.

License

MIT