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A complete GELF client, server, and proxy for Graylog
Latest commit 88de337 @wavded Break out license file

GrayGelf Build Status Coverage Status

GrayLog2 GELF UDP logging, streaming, chunking, and more. Production tested. Includes client and server implementations. AFAIK a complete GELF implementation.



npm install graygelf



var log = require('graygelf')('graylog.server.local')
log.on('message', console.log) // output messages to console

// setup global custom fields to be passed with every message
log.fields.facility = 'redicomps'

// printf style "hello world"'hello %s', 'world')

// concat by space style "hello world"'hello', 'world')

// stays context aware
redis.on('error', log.error)

// include a full message and custom fields using .a(ttach)'short', 'full', { foo: 'bar' })'short', 'full', { foo: 'bar' })

// if an Error is passed as the only argument...
var er = new Error('oh no!')
// ... it expands to:, er.stack)

// writable streams can be created
var infostream ='info')
var rstream = require('fs').createReadStream(__filename)
rstream.pipe(infostream) // lines automatically split up and sent seperately

// raw gelf: version, host, and timestamp will be supplied if missing
  // version: '1.1',
  // host: 'wavded',
  short_message: 'oh no!',
  full_message: 'howdy',
  // timestamp: 1412087767.704356,
  level: 6,
  _foo: 'bar'


By host string (uses defaults below for other options):

var log = require('graygelf')('graylog.server.local')

By options object:

var log = require('graygelf'){{
  host: 'graylog.server.local',
  port: 23923

Available options are:

  - graylog host (default: 'localhost')
  - graylog port (default: 12201)
  - size of chunked messages in bytes (default: 1240)
  - compression 'gzip' or 'deflate' (default: 'deflate')
  - don't send messages to GrayLog2 (default: false)


event: error

Emits errors that may occur while parsing and sending GELF messages.

event: message

Emits GELF JSON messages that will be send over UDP. Useful for redirecting output to stdout in development.

log.on('message', function (gelf) {
  console.log(gelf.level, gelf.short_message, gelf.long_message)


Add global custom fields to be included in every message. Custom fields allow you to more interesting searches and sorting inside GrayLog2 servers.

log.fields.facility = 'facility'

Note: fields is plain JavaScript object.


GrayGelf maps the syslog levels to functions. All functions have the same semantics as console.log (i.e. printf style):

log.emerg('oh %s', 's*#t')              // 0 - alias: panic
log.alert('act', 'immediately')         // 1
log.crit('act %j', [ 'really soon' ])   // 2
log.error('expected %d, got %d', 1, 5)  // 3 - alias: err
log.warn('take note, it may bite')      // 4 - alias: warning
log.notice('unusual %s', 'behavior')    // 5'hello', 'world')              // 6
log.debug('value is', a)                // 7

log{level}.a(short, long, custom)

There also is an a(ttach) method to include a full message.

log.crit.a('short message', 'full message')

The a(ttach) method can have an optional third argument to define custom fields that will be passed to Graylog2.'short message', 'full message', { custom: 'field' })

Create a writable stream to pipe log messages into:

var stream ='info')

Streams automatically break lines up and pass each line to GrayLog2 at the specified level.


Pass a raw GELF message. The following fields will be populated if absent: version, host, and timestamp.

  version: '1.1',
  host: 'wavded',
  short_message: 'oh no!',
  full_message: 'howdy',
  timestamp: 1412087767.704356,
  level: 6,
  _foo: 'custom field'

Note: No global custom fields (log.fields) are included when using log.raw.


Make your own GrayLog UDP server or proxy messages to GrayLog. A GrayGelf server handles zlib, gzip and GELF chunked messages.


var gelfserver = require('graygelf/server')
var server = gelfserver()
server.on('message', function (gelf) {
  // handle parsed gelf json
  console.log('received message', gelf.short_message)

event: message

Emits parsed GELF JSON messages.

event: data

Emits raw GELF buffers (useful for proxying).

event: error

Emits errors captured from udp or parsing.

server.listen(port = 12201, address = "")

Start listening on a port and bind address. Both parameters are optional. Defaults to typical GrayLog2 server defaults.


Close down a server and stop receiving messages.


Allow the Node process to terminate if the server is the only thing keeping it alive.


var server = require('graygelf/server')().listen()
var client = require('graygelf')('proxy-dest.graylog.local')

server.pipe(client) // establish proxy (straight UDP transfer)
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