This article explains how to monitor the Fluentd daemon.
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:3fec669daf98","type":"http","output_plugin":false,"config":{"type":"http","port":"8888"}},{"plugin_id":"object:3fec669dfa48","type":"monitor_agent","output_plugin":false,"config":{"type":"monitor_agent","port":"24220"}},{"plugin_id":"object:3fec66a52e94","type":"debug_agent","output_plugin":false,"config":{"type":"debug_agent","port":"24230"}},{"plugin_id":"object:3fec66ae3dcc","type":"stdout","output_plugin":true,"config":{"type":"stdout"}},{"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"}}]}%
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
If you are using td-agent 1, Ruby's path is /usr/lib/fluent/ruby/bin/ruby, not /opt/td-agent/embedded/bin/ruby.
Fluentd opens several ports according to the configuration file. We recommend checking the availability of these ports. The default port settings are shown below:
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.