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The @fluent-org/logger library is used to post records from Node.js applications to Fluentd.
This article explains how to use it.
NOTE: The previous NPM package, fluent-logger has been deprecated in favor of @fluent-org/logger.
Prerequisites
Basic knowledge of Node.js and NPM
Basic knowledge of Fluentd
Node.js 12.0 or higher
Installing Fluentd
Please refer to the following documents to install fluentd:
​Install Fluentd with rpm Package​
​Install Fluentd with deb Package​
​Install Fluentd with Ruby Gem​
​Install Fluentd from source​
Modifying the Config File
Configure Fluentd to use the forward input plugin as its data source:
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<source>
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  @type forward
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  port 24224
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</source>
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<match fluentd.test.**>
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  @type stdout
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</match>
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Restart agent after configuring.
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# for rpm/deb only
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$ sudo /etc/init.d/td-agent restart
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​
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# or systemd
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$ sudo systemctl restart td-agent.service
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Using @fluent-org/logger
Obtaining the Most Recent Version
The most recent version of @fluent-org/logger can be found here.
A Sample Application
Here is a sample Express app using @fluent-org/logger:
package.json
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{
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  "name": "node-example",
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  "version": "0.0.1",
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  "dependencies": {
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    "express": "^4.16.0",
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    "@fluent-org/logger": "^1.0.2"
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  }
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}
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Use npm to install dependencies locally:
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$ npm install
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index.js
This is a simple web app:
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const express = require('express');
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const FluentClient = require('@fluent-org/logger').FluentClient;
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const app = express();
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​
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// The 2nd argument can be omitted. Here is a default value for options.
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const logger = new FluentClient('fluentd.test', {
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  socket: {
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    host: 'localhost',
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    port: 24224,
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    timeout: 3000, // 3 seconds
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  }
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});
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​
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app.get('/', function(request, response) {
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  logger.emit('follow', {from: 'userA', to: 'userB'});
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  response.send('Hello World!');
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});
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const port = process.env.PORT || 3000;
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app.listen(port, function() {
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  console.log("Listening on " + port);
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});
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Run the app and go to http://localhost:3000/ in your browser to send the logs to Fluentd:
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$ node index.js
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The logs should be output to /var/log/td-agent/td-agent.log or the standard output of the Fluentd process via stdout output plugin.
Production Deployments
Output Plugins
Various output plugins are available for writing records to other destinations:
Examples
​Store Apache Logs into Amazon S3​
​Store Apache Logs into MongoDB​
​Data Collection into HDFS​
List of Plugin References
​Output to Another Fluentd​
​Output to MongoDB or MongoDB ReplicaSet​
​Output to Hadoop​
​Output to File​
​etc...​
High-Availability Configurations of Fluentd
For high-traffic websites (more than 5 application nodes), we recommend using the high-availability configuration for td-agent. This will improve the reliability of data transfer and query performance.
​High-Availability Configurations of Fluentd​
Monitoring
Monitoring Fluentd itself is also important. The article below describes the general monitoring methods for td-agent.
​Monitoring Fluentd​
If this article is incorrect or outdated, or omits critical information, please let us know. Fluentd is an open-source project under Cloud Native Computing Foundation (CNCF). All components are available under the Apache 2 License.