Versions | v0.12 (td-agent2) | v0.10 (td-agent1)

Centralize Logs from Node.js Applications

The ‘fluent-logger-node’ library is used to post records from Node.js applications to Fluentd.

This article explains how to use the fluent-logger-node library.

Table of Contents


  • Basic knowledge of Node.js and NPM
  • Basic knowledge of Fluentd
  • Node.js 0.6 or higher

Installing Fluentd

Please refer to the following documents to install fluentd.

Modifying the Config File

Next, please configure Fluentd to use the forward Input plugin as its data source.

  @type forward
  port 24224
<match fluentd.test.**>
  @type stdout

Please restart your agent once these lines are in place.

# for rpm/deb only
$ sudo /etc/init.d/td-agent restart

Using fluent-logger-node

Obtaining the Most Recent Version

The most recent version of fluent-logger-node can be found here.

A Sample Application

A sample Express app using fluent-logger-node is shown below.


  "name": "node-example",
  "version": "0.0.1",
  "dependencies": {
    "express": "2.5.9",
    "fluent-logger": "0.1.0"

Now use npm to install your dependencies locally:

$ npm install
fluent-logger@0.1.0 ./node_modules/fluent-logger
express@2.5.9 ./node_modules/express
|-- qs@0.4.2
|-- mime@1.2.4
|-- mkdirp@0.3.0
|-- connect@1.8.6 (formidable@1.0.9)


This is the simplest web app.

var express = require('express');
var app = express.createServer(express.logger());

var logger = require('fluent-logger');
logger.configure('fluentd.test', {host: 'localhost', port: 24224});

app.get('/', function(request, response) {
  logger.emit('follow', {from: 'userA', to: 'userB'});
  response.send('Hello World!');
var port = process.env.PORT || 3000;
app.listen(port, function() {
  console.log("Listening on " + port);

Execute the app and go to http://localhost:3000/ in your browser. This will send the logs to Fluentd.

$ node web.js

The logs should be output to /var/log/td-agent/td-agent.log or stdout of the Fluentd process via the stdout Output plugin.

Production Deployments

Output Plugins

Various output plugins are available for writing records to other destinations:

High-Availability Configurations of Fluentd

For high-traffic websites (more than 5 application nodes), we recommend using a high availability configuration of td-agent. This will improve data transfer reliability and query performance.


Monitoring Fluentd itself is also important. The article below describes general monitoring methods for td-agent.

Last updated: 2015-12-01 21:20:32 UTC

Versions | v0.12 (td-agent2) | v0.10 (td-agent1)

If this article is incorrect or outdated, or omits critical information, please let us know. Fluentd is a open source project under Cloud Native Computing Foundation (CNCF), originally invented by Treasure Data, Inc. All components are available under the Apache 2 License.

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