theconnman/fluent-logger-node

A structured logger for Fluentd (Node.js)

fluent-logger for Node.js

fluent-logger implementation for Node.js inspired by fluent-logger-python.

Install

$ npm install fluent-logger

Prerequistes

Fluent daemon should listen on TCP port.

Simple configuration is following:

<source>
  @type forward
  port 24224
</source>

<match **.*>
  @type stdout
</match>

Usage

Send an event record to Fluentd

Singleton style

var logger = require('fluent-logger')
// The 2nd argument can be omitted. Here is a default value for options.
logger.configure('tag_prefix', {
   host: 'localhost',
   port: 24224,
   timeout: 3.0,
   reconnectInterval: 600000 // 10 minutes
});

// send an event record with 'tag.label'
logger.emit('label', {record: 'this is a log'});

Instance style

var logger = require('fluent-logger').createFluentSender('tag_prefix', {
   host: 'localhost',
   port: 24224,
   timeout: 3.0,
   reconnectInterval: 600000 // 10 minutes
});

The emit method has following signature

.emit([label string], <record object>, [timestamp number/date], [callback function])

Where only the record argument is required. If the label is set it will be appended to the configured tag.

EventTime support

We can also specify EventTime as timestamp.

var FluentLogger = require('fluent-logger');
var EventTime = FluentLogger.EventTime;
var logger = FluentLogger.createFluentSender('tag_prefix', {
var eventTime = new EventTime(1489547207, 745003500); // 2017-03-15 12:06:47 +0900
logger.emit('tag', { message: 'This is a message' }, eventTime);

Events

• connect : Handle net.Socket Event: connect
• error : Handle net.Socket Event: error

var logger = require('fluent-logger').createFluentSender('tag_prefix', {
   host: 'localhost',
   port: 24224,
   timeout: 3.0,
   reconnectInterval: 600000 // 10 minutes
});
logger.on('error', function(error) {
  console.log(error);
});
logger.on('connect', function() {
  console.log('connected!');
});

Logging Library Support

log4js

Before using [log4js] support, you should install it IN YOUR APPLICATION.

var log4js = require('log4js');
log4js.addAppender(require('fluent-logger').support.log4jsAppender('mytag', {
   host: 'localhost',
   port: 24224,
   timeout: 3.0
}));

var logger = log4js.getLogger('foo');
logger.info('this log record is sent to fluent daemon');

You can add log level after tag automatically.

var log4js = require('log4js');
log4js.addAppender(require('fluent-logger').support.log4jsAppender('mytag', {
   host: 'localhost',
   port: 24224,
   timeout: 3.0,
   levelTag: true
}));

var logger = log4js.getLogger('foo');
logger.info('this log record is sent to fluent daemon');

If levelTag is true, tag is "mytag.INFO". If levelTag is false, tag is "mytag".

You can handle inner events such as 'error' it is raised when fluentd is down.

var log4js = require('log4js');
var appender = require('fluent-logger').support.log4jsAppender('mytag', {
  host: 'localhost',
  port: 24224,
  timeout: 3.0
});
appender.on('error', function(err) {
  // Handle err object
  console.log(err);
});
log4js.addAppender(appender);

winston

Before using winston support, you should install it IN YOUR APPLICATION.

var winston = require('winston');
var config = {
  host: 'localhost',
  port: 24224,
  timeout: 3.0
};
var fluentTransport = require('fluent-logger').support.winstonTransport();
var logger = new (winston.Logger)({
    transports: [new fluentTransport('mytag', config), new (winston.transports.Console)()]
});

logger.log('info', 'this log record is sent to fluent daemon');
logger.info('this log record is sent to fluent daemon');

stream

Several libraries use stream as output.

var sender = require('fluent-logger').createFluentSender('tag_prefix', {
   host: 'localhost',
   port: 24224,
   timeout: 3.0,
   reconnectInterval: 600000 // 10 minutes
});
var logger = new Console(sender.toStream('stdout'), sender.toStream('stderr'));
logger.log('this log record is sent to fluent daemon');

Options

tag_prefix

The tag prefix string. You can specify null when you use FluentSender directly. In this case, you must specify label when you call emit.

host

The hostname. Default value = 'localhost'.

See socket.connect

port

The port to listen to. Default value = 24224.

See socket.connect

path

The path to your Unix Domain Socket. If you set path then fluent-logger ignores host and port.

See socket.connect

timeout

Set the socket to timetout after timeout milliseconds of inactivity on the socket.

See socket.setTimeout

reconnectInterval

Set the reconnect interval in milliseconds. If error occurs then reconnect after this interval.

requireAckResponse

Change the protocol to at-least-once. The logger waits the ack from destination.

ackResponseTimeout

This option is used when requireAckResponse is true. The default is 190. This default value is based on popular tcp_syn_retries.

tags

Inject additional data into every message. This is useful for environment tags or application functions. For example:

tags: {
  env: 'DEV',
  function: 'API'
}

License

Apache License, Version 2.0.

Abour NodeJS versions

This package is compatible with NodeJS versions > 4.