Document version: v0.12

Monitoring Fluentd

This article explains how to monitor the Fluentd daemon.

Table of Contents

Monitoring Agent

Fluentd has a monitoring agent to retrieve internal metrics in JSON via HTTP. Please add the following lines to your configuration file.

<source>
  @type monitor_agent
  bind 0.0.0.0
  port 24220
</source>

Next, please restart the agent and get the metrics via HTTP.

$ curl http://host:24220/api/plugins.json
{
  "plugins":[
    {
      "plugin_id":"object:3fec669d6ac4",
      "type":"forward",
      "output_plugin":false,
      "config":{
        "type":"forward"
      }
    },
    {
      "plugin_id":"object:3fec669dfa48",
      "type":"monitor_agent",
      "output_plugin":false,
      "config":{
        "type":"monitor_agent",
        "port":"24220"
      }
    },
    {
      "plugin_id":"object:3fec66aead48",
      "type":"forward",
      "output_plugin":true,
      "buffer_queue_length":0,
      "buffer_total_queued_size":0,
      "retry_count":0,
      "config":{
        "type":"forward",
        "host":"192.168.0.11"
      }
    }
  ]
}

Reuse plugins

Since v0.12.17, monitor_agent plugin has tag parameter. If you set tag monitor.metrics, monitor_agent plugin emits internal metrics to monitor.metrics tag. Here is an example with stdout output.

2015-09-16 20:28:19 +0900 monitor.metrics: {"plugin_id":"object:3fc62f0e5d64","plugin_category":"input","type":"monitor_agent","output_plugin":false,"retry_count":null}
2015-09-16 20:28:19 +0900 monitor.metrics: {"plugin_id":"object:3fc62f0e9c84","plugin_category":"output","type":"stdout","output_plugin":true,"retry_count":null}

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.

Last updated: 2016-03-21 17:32:59 UTC

Available versions | v0.10 | v0.12 |

If this article is incorrect or outdated, or omits critical information, please let us know.

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