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The fluent-logger-java library is used to post records from Java applications to Fluentd.
This article explains how to use it.


  • Basic knowledge of Java
  • Basic knowledge of Fluentd
  • Java 7 or higher

Installing Fluentd

Please refer to the following documents to install fluentd:

Modifying the Config File

Configure Fluentd to use the forward input plugin as its data source:
@type forward
port 24224
<match fluentd.test.**>
@type stdout
Restart agent after configuring.
# for rpm/deb only
$ sudo /etc/init.d/td-agent restart
# or systemd
$ sudo systemctl restart td-agent.service

Using fluent-logger-java

Add the following dependency configuration to pom.xml. The logger's revision information can be found in CHANGES.txt:
Here's a sample Java test application:
import java.util.HashMap;
import java.util.Map;
import org.fluentd.logger.FluentLogger;
public class Main {
private static FluentLogger LOG = FluentLogger.getLogger("fluentd.test");
public void doApplicationLogic() {
// ...
Map<String, Object> data = new HashMap<String, Object>();
data.put("from", "userA");
data.put("to", "userB");
LOG.log("follow", data);
// ...
More information on the Java API can be found here.
Executing the above program will send the logs to Fluentd:
$ java -jar test.jar
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:

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.


Monitoring Fluentd itself is also important. The article below describes the general monitoring methods for td-agent:
If this article is incorrect or outdated, or omits critical information, please let us know.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.