in_statsd: Add a description for Metrics parameter

pipeline/inputs/statsd.md

@@ -16,6 +16,13 @@ The plugin supports the following configuration parameters:
 | Listen | Listener network interface. | 0.0.0.0 |
 | Port | UDP port where listening for connections | 8125 |
 | Threaded | Indicates whether to run this input in its own [thread](../../administration/multithreading.md#inputs). | `false` |
+| Metrics | Ingested record will be marked as a metric record rather than a log record. | `off` |
+
+Note: When enabling `Metrics On`, we will also handle metrics from the DogStatsD protocol and the internal record in Fluent Bit will be handled as a metric type for downstream processing.
+[The full format of DogStatsD of metrics](https://docs.datadoghq.com/developers/dogstatsd/datagram_shell/?tab=metrics#the-dogstatsd-protocol) is not supported.
+Including key-value format of tags as below is supported:
+`<METRIC_NAME>:<VALUE>|<TYPE>|@<SAMPLE_RATE>|#<TAG_KEY_1>:<TAG_VALUE_1>`
+[Events](https://docs.datadoghq.com/developers/dogstatsd/datagram_shell/?tab=events#the-dogstatsd-protocol) and [ServiceChecks](https://docs.datadoghq.com/developers/dogstatsd/datagram_shell/?tab=servicechecks#the-dogstatsd-protocol) formats are not supported yet with `Metrics On`.
 
 ## Configuration Examples <a id="config_example"></a>
 
@@ -62,3 +69,53 @@ Fluent Bit will produce the following records:
 [0] statsd.0: [1574905088.971380537, {"type"=>"counter", "bucket"=>"click", "value"=>10.000000, "sample_rate"=>0.100000}]
 [0] statsd.0: [1574905141.863344517, {"type"=>"gauge", "bucket"=>"active", "value"=>99.000000, "incremental"=>0}]
 ```
+
+## Metrics Setup
+
+Here is a configuration example for metrics setup.
+
+{% tabs %}
+{% tab title="fluent-bit.conf" %}
+```python
+[INPUT]
+    Name   statsd
+    Listen 0.0.0.0
+    Port   8125
+    Metrics On
+
+[OUTPUT]
+    Name   stdout
+    Match  *
+```
+{% endtab %}
+
+{% tab title="fluent-bit.yaml" %}
+```yaml
+pipeline:
+    inputs:
+        - name: statsd
+          listen: 0.0.0.0
+          port: 8125
+          metrics: On
+    outputs:
+        - name: stdout
+          match: '*'
+```
+{% endtab %}
+{% endtabs %}
+
+Now you can input metrics as metrics type of events through the UDP port as follows:
+
+```bash
+echo "click:+10|c|@0.01|#hello:tag"              | nc -q0 -u 127.0.0.1 8125
+echo "active:+99|g|@0.01"                        | nc -q0 -u 127.0.0.1 8125
+echo "inactive:29|g|@0.0125|#hi:from_fluent-bit" | nc -q0 -u 127.0.0.1 8125
+```
+
+Fluent Bit will procude the following metrics events:
+
+```
+2025-01-09T11:40:26.562424694Z click{incremental="true",hello="tag"} = 1000
+2025-01-09T11:40:28.591477424Z active{incremental="true"} = 9900
+2025-01-09T11:40:31.593118033Z inactive{hi="from_fluent-bit"} = 2320
+```