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description A plugin to collect Fluent Bit metrics

Fluent Bit metrics

{% hint style="info" %} Supported event types: metrics {% endhint %}

Fluent Bit exposes metrics to let you monitor the internals of your pipeline. The collected metrics can be processed similarly to those from the Prometheus Node Exporter input plugin. They can be sent to output plugins including Prometheus Exporter, Prometheus Remote Write or OpenTelemetry.

{% hint style="info" %}

Metrics collected with Fluent Bit Metrics flow through a separate pipeline from logs and current filters don't operate on top of metrics.

{% endhint %}

Configuration parameters

Key Description Default
scrape_interval The rate at which Fluent Bit internal metrics are collected. 2 seconds
scrape_on_start Scrape metrics upon start, use to avoid waiting for scrape_interval for the first round of metrics. false
threaded Indicates whether to run this input in its own thread. false

Get started

You can run the plugin from the command line or through the configuration file:

Command line

Run the plugin from the command line using the following command:

fluent-bit -i fluentbit_metrics -o stdout

which returns results like the following:

...
[2025/12/02 08:33:54.689265000] [ info] [input:fluentbit_metrics:fluentbit_metrics.0] initializing
[2025/12/02 08:33:54.689272000] [ info] [input:fluentbit_metrics:fluentbit_metrics.0] storage_strategy='memory' (memory only)
[2025/12/02 08:33:54.689917000] [ info] [output:stdout:stdout.0] worker #0 started
[2025/12/02 08:33:54.690115000] [ info] [sp] stream processor started
[2025/12/02 08:33:54.690204000] [ info] [engine] Shutdown Grace Period=5, Shutdown Input Grace Period=2
2025-12-02T07:33:56.692855536Z fluentbit_uptime{hostname="XXXXX.local"} = 2
2025-12-02T07:33:54.687838528Z fluentbit_logger_logs_total{message_type="error"} = 0
2025-12-02T07:33:54.687838528Z fluentbit_logger_logs_total{message_type="warn"} = 0
2025-12-02T07:33:54.690212675Z fluentbit_logger_logs_total{message_type="info"} = 10
2025-12-02T07:33:54.687838528Z fluentbit_logger_logs_total{message_type="debug"} = 0
2025-12-02T07:33:54.687838528Z fluentbit_logger_logs_total{message_type="trace"} = 0
2025-12-02T07:33:54.689222850Z fluentbit_input_bytes_total{name="fluentbit_metrics.0"} = 0
2025-12-02T07:33:54.689222850Z fluentbit_input_records_total{name="fluentbit_metrics.0"} = 0
2025-12-02T07:33:54.689222850Z fluentbit_input_ring_buffer_writes_total{name="fluentbit_metrics.0"} = 0
2025-12-02T07:33:54.689222850Z fluentbit_input_ring_buffer_retries_total{name="fluentbit_metrics.0"} = 0
2025-12-02T07:33:54.689222850Z fluentbit_input_ring_buffer_retry_failures_total{name="fluentbit_metrics.0"} = 0
2025-12-02T07:33:56.692846827Z fluentbit_input_metrics_scrapes_total{name="fluentbit_metrics.0"} = 1
2025-12-02T07:33:54.689563930Z fluentbit_output_proc_records_total{name="stdout.0"} = 0
...

Configuration file

In the following configuration file, the input plugin fluentbit_metrics collects metrics every 2 seconds and exposes them through the Prometheus Exporter output plugin on HTTP/TCP port 2021.

{% tabs %} {% tab title="fluent-bit.yaml" %}

service:
  flush: 1
  log_level: info

pipeline:
  inputs:
    - name: fluentbit_metrics
      tag: internal_metrics
      scrape_interval: 2

  outputs:
    - name: prometheus_exporter
      match: internal_metrics
      host: 0.0.0.0
      port: 2021

{% endtab %} {% tab title="fluent-bit.conf" %}

# Fluent Bit Metrics + Prometheus Exporter
# -------------------------------------------
# The following example collects Fluent Bit metrics and exposes
# them through a Prometheus HTTP endpoint.
#
# After starting the service try it with:
#
# $ curl http://127.0.0.1:2021/metrics
#
[SERVICE]
  flush           1
  log_level       info

[INPUT]
  name            fluentbit_metrics
  tag             internal_metrics
  scrape_interval 2

[OUTPUT]
  name            prometheus_exporter
  match           internal_metrics
  host            0.0.0.0
  port            2021

{% endtab %} {% endtabs %}

You can test the expose of the metrics by using curl:

curl http://127.0.0.1:2021/metrics