pino-multi-stream

A wrapper for the Pino logger that provides Bunyan's multipe destination stream API

Usage no npm install needed!

<script type="module">
  import pinoMultiStream from 'https://cdn.skypack.dev/pino-multi-stream';
</script>

README

pino-multi-stream CI

pino-multi-stream is a wrapper around the pino logger. The purpose of pino-multi-stream is to provide a stop-gap method for migrating from the Bunyan logger. Whereas pino allows only one destination stream, pino-multi-stream allows multiple destination streams via the same configuration API as Bunyan.

Please see the caveats section for some important information regarding the performance of this module.

Install

For Pino v5+

npm install -s pino-multi-stream

For Pino v4 and below:

npm install -s pino-multi-stream@legacy #v3 pino-multi-stream line

pino-multi-stream does not provide the CLI that pino provides. Therefore, you should not install it globally.

Usage

var fs = require('fs')
var pinoms = require('pino-multi-stream')
var streams = [
  {stream: fs.createWriteStream('/tmp/info.stream.out')},
  {level: 'fatal', stream: fs.createWriteStream('/tmp/fatal.stream.out')}
]
var log = pinoms({streams: streams})

log.info('this will be written to /tmp/info.stream.out')
log.fatal('this will be written to /tmp/fatal.stream.out')

API

The API for pino-multi-stream is the same as that for pino. Please read pino's documentation for full details. Highlighted here are the specifics for pino-multi-stream:

  • The signature for constructor remains the same, pino(opts, stream), but there are a few conditions under which you may get a real pino instance or one wrapped by pino-multi-stream:

    1. If the opts parameter is a writable stream, then a real pino instance will be returned.
  1. If the opts parameter is an object with a singular stream property then a real pino instance will be returned. If there is also a plural streams property, the singular stream property takes precedence.
  2. If the opts parameter is an object with a plural streams property, does not include a singluar stream property, and is an array, then a pino-multi-stream wrapped instance will be returned. Otherwise, opts.streams is treated a single stream and a real pino instance will be returned.
  • The pino options object accepts a streams option, as alluded to in then previous item. This option should be an array of stream objects. A stream object is one with at least a stream property and, optionally, a level property. For example:

    var logger = pinoms({
      streams: [
        {stream: process.stdout}, // an "info" level destination stream
        {level: 'error', stream: process.stderr} // an "error" level destination stream
      ]
    })
    

pinoms.multistream(streams, opts)

Manually create a single multistream as used internally by the wrapper:

var fs = require('fs')
var pino = require('pino')
var multistream = require('pino-multi-stream').multistream
var streams = [
  {stream: fs.createWriteStream('/tmp/info.stream.out')},
  {level: 'debug', stream: fs.createWriteStream('/tmp/debug.stream.out')},
  {level: 'fatal', stream: fs.createWriteStream('/tmp/fatal.stream.out')}
]

var log = pino({
  level: 'debug' // this MUST be set at the lowest level of the
                 // destinations
}, multistream(streams))

log.debug('this will be written to /tmp/debug.stream.out')
log.info('this will be written to /tmp/debug.stream.out and /tmp/info.stream.out')
log.fatal('this will be written to /tmp/debug.stream.out, /tmp/info.stream.out and /tmp/fatal.stream.out')

opts multistream options object. Available options are:

  • levels: Pass custom log level definitions to the instance as an object.
  • dedupe: Set this to true to send logs only to the stream with the higher level. Default: false

    dedupe flag can be useful for example when using pino-multi-stream to redirect error logs to process.stderr and others to process.stdout:

    var pino = require('pino')
    var multistream = require('pino-multi-stream').multistream
    var streams = [
      {stream: process.stdout},
      {level: 'error', stream: process.stderr},
    ]
    
    var opts = {
        levels: {
            silent: Infinity,
            fatal: 60,
            error: 50,
            warn: 50,
            info: 30,
            debug: 20,
            trace: 10
        },
        dedupe: true,
    }
    
    var log = pino({
      level: 'debug' // this MUST be set at the lowest level of the
                    // destinations
    }, multistream(streams, opts))
    
    log.debug('this will be written ONLY to process.stdout')
    log.info('this will be written ONLY to process.stdout')
    log.error('this will be written ONLY to process.stderr')
    log.fatal('this will be written ONLY to process.stderr')
    

pinoms.level set accessor

You can set the level to all streams by changing the level property. It accepts the same parameters as pino. If the level is changed on a child logger, it does not alter the parent streams level. As this is costly operation, we recommend not changing the level for each child logger that is being created.

pinoms.level get accessor

The behavior of the get accessor changes if { bunyan: true } is passed to pinoms. In that case, it implements the bunyan.level function.

pinoms.prettyStream({ [prettyPrint], [prettifier], [dest] })

Note: after 4.1.0 this pino-multi-stream function was changed according to that of pino, and after 4.2.0 its API (names of parameters and their options) are in conformity with API of pino/pino-pretty, as it is presented here. Those changes are related to pretty-printing options only.

Manually create an output stream with a prettifier applied.

var fs = require('fs');
var pinoms = require('pino-multi-stream')

var prettyStream = pinoms.prettyStream()
var streams = [
    {stream: fs.createWriteStream('my.log') },
    {stream: prettyStream }
]

var logger = pinoms(pinoms.multistream(streams))

logger.info("HELLO %s!", "World")

The options object may additionally contain a prettifier property to define which prettifier module to use. When not present, prettifier defaults to pino-pretty (must be installed as a separate dependency).

The method may be passed an alternative write destination, but defaults to process.stdout.

Prettifying options (after 4.2.0) are to be set like this:

const prettyStream = pinoms.prettyStream(
{
 prettyPrint:
  { colorize: true,
    translateTime: "SYS:standard",
    ignore: "hostname,pid" // add 'time' to remove timestamp
  },
 prettifier: require('pino-pretty') // not required, just an example of setting prettifier
    // as well it is possible to set destination option
}
);

Caveats

Stern warning: the performance of this module being dependent on the number of streams you supply cannot be overstated. This module is being provided so that you can switch to pino from Bunyan and get some immediate improvement, but it is not meant to be a long term solution. We strongly suggest that you use this module for only as long as it will take you to overhaul the way you handle logging in your application. pino-multi-stream offers close to zero overhead if there is only one destination stream.

To illustrate what we mean, here is a benchmark of pino and Bunyan using "multiple" streams to write to a single stream:

benchBunyanOne*10000: 703.071ms
benchPinoMSOne*10000: 287.060ms

Now let's look at the same benchmark but increase the number of destination streams to four:

benchBunyanFour*10000: 2249.955ms
benchPinoMSFour*10000: 1017.886ms

And, finally, with ten destination streams:

benchBunyanTen*10000: 4950.301ms
benchPinoMSTen*10000: 3127.361ms

License

MIT License