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

The following writes the log output of app.js to ./all-logs, while writing only warnings and errors to `./warn-log:

node app.js | pino-tee warn ./warn-logs > ./all-logs

NodeJS

You can log to multiple files by spawning a child process:

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});
 
logThrough.pipe(child.stdin);
 
// Log pretty messages to console (optional, for development purposes only)
const pretty = pino.pretty();
pretty.pipe(process.stdout);
logThrough.pipe(pretty);

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