This article describes how to monitor Fluentd.

Fluentd Metrics Monitoring

Fluentd can expose internal metrics via REST API, and works with monitoring tools such as Prometheus, Datadog, etc. Our recommendation is to use Prometheus, since we will be collaborating more in the future under the CNCF (Cloud Native Computing Foundation).

Process Monitoring

Two ruby processes (parent and child) are executed. Please make sure that these processes are running.

Here's an example for td-agent:

/opt/td-agent/embedded/bin/ruby /usr/sbin/td-agent
  --daemon /var/run/td-agent/td-agent.pid
  --log /var/log/td-agent/td-agent.log

For td-agent on Linux, check the process statuses like this:

$ ps w -C ruby -C td-agent --no-heading
32342 ?        Sl     0:00 /opt/td-agent/embedded/bin/ruby /usr/sbin/td-agent --daemon /var/run/td-agent/td-agent.pid --log /var/log/td-agent/td-agent.log
32345 ?        Sl     0:01 /opt/td-agent/embedded/bin/ruby /usr/sbin/td-agent --daemon /var/run/td-agent/td-agent.pid --log /var/log/td-agent/td-agent.log

There should be two processes if there is no issue.

Port Monitoring

Fluentd opens several ports according to the configuration file. We recommend checking the availability of these ports. The default port settings are shown below:

  • TCP 9880 (HTTP by default)

  • TCP 24224 (Forward by default)

Debug Port

A debug port for local communication is recommended for troubleshooting. The following configuration will be required for the debug port:

  @type debug_agent
  port 24230

You can attach the process using the fluent-debug command through dRuby.

If this article is incorrect or outdated, or omits critical information, please let us know.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.

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