# Monitoring

This article desribes how to monitor Fluentd.

## Fluentd Metrics Monitoring

Fluentd can expose internal metrics via REST API, and works with monitoring tools such as [Prometheus](https://prometheus.io/), [Datadog](https://www.datadoghq.com/), etc. Our recommendation is to use Prometheus, since we will be collaborating more in the future under the [CNCF (Cloud Native Computing Foundation)](https://www.cncf.io/).

* [Monitoring Fluentd (Prometheus)](https://docs.fluentd.org/0.12/articles/monitoring-prometheus)
* [Monitoring Fluentd (Datadog)](https://docs.datadoghq.com/integrations/fluentd/)
* [Monitoring Fluentd (REST API)](https://docs.fluentd.org/0.12/articles/monitoring-rest-api)

## Process Monitoring

Two `ruby` processes (parent and child) are executed. Please make sure that these processes are running. The example for `td-agent` is shown below.

```
/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, you can check the process statuses with the following command. Two processes should be shown if there are no issues.

```
$ 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
```

## 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 0.0.0.0 9880 (HTTP by default)
* TCP 0.0.0.0 24224 (Forward by default)

## Debug Port

A debug port for local communication is recommended for trouble shooting. Please note that the configuration below will be required.

```
<source>
  @type debug_agent
  bind 127.0.0.1
  port 24230
</source>
```

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If this article is incorrect or outdated, or omits critical information, please [let us know](https://github.com/fluent/fluentd-docs-gitbook/issues?state=open). [Fluentd](http://www.fluentd.org/) is a open source project under [Cloud Native Computing Foundation (CNCF)](https://cncf.io/). All components are available under the Apache 2 License.