processor_metrics_selector: Add documents for metrics_selector processor (fluent#1340)

* processor_metrics_selector: Add documents for metrics_selector processor

Signed-off-by: Hiroshi Hatake <hiroshi@chronosphere.io>

* Update installation/sources/build-and-install.md

Co-authored-by: Pat <pat@calyptia.com>
Signed-off-by: Hiroshi Hatake <hatake@calyptia.com>

* Update pipeline/processors/metrics-selector.md

Co-authored-by: Pat <pat@calyptia.com>
Signed-off-by: Hiroshi Hatake <hatake@calyptia.com>

* Update pipeline/processors/metrics-selector.md

Co-authored-by: Pat <pat@calyptia.com>
Signed-off-by: Hiroshi Hatake <hatake@calyptia.com>

* processor_metrics_selector: Add a example description for a making regular expression

Signed-off-by: Hiroshi Hatake <hiroshi@chronosphere.io>

---------

Signed-off-by: Hiroshi Hatake <hiroshi@chronosphere.io>
Signed-off-by: Hiroshi Hatake <hatake@calyptia.com>
Co-authored-by: Pat <pat@calyptia.com>

Author: cosmo0920

.gitbook.yaml

@@ -76,3 +76,6 @@ redirects:
     output/stdout:         ./pipeline/outputs/standard-output.md
     output/tcp:            ./pipeline/outputs/tcp-and-tls.md
     output/td:             ./pipeline/outputs/treasure-data.md
+
+    # Processors
+    processor/metrics_selector:   ./pipeline/processors/metrics_selector.md

SUMMARY.md

@@ -194,6 +194,8 @@
   * [Treasure Data](pipeline/outputs/treasure-data.md)
   * [Vivo Exporter](pipeline/outputs/vivo-exporter.md)
   * [WebSocket](pipeline/outputs/websocket.md)
+* [Processors](pipeline/processors/README.md)
+  * [Metrics Selector](pipeline/processors/metrics-selector.md)
 
 ## Stream Processing
 

installation/sources/build-and-install.md

@@ -212,3 +212,11 @@ The _output plugins_ gives the capacity to flush the information to some externa
 | FLB\_OUT\_TCP | Enable TCP/TLS output plugin | On |
 | [FLB\_OUT\_TD](../../pipeline/outputs/treasure-data.md) | Enable [Treasure Data](http://www.treasuredata.com) output plugin | On |
 
+### Processor Plugins
+
+The _processor plugins_ provide the capability to handle the events within the processor pipelines to allow modifying, enrich or drop events. 
+The following table describes the processors available on this version:
+
+| option | description | default |
+| :--- | :--- | :--- |
+| [FLB\_PROCESSOR\_METRICS\_SELECTOR](../../pipeline/processors/metrics-selector.md) | Enable metrics selector processor | On |

pipeline/processors/README.md

@@ -0,0 +1,2 @@
+# Processors
+

pipeline/processors/metrics-selector.md

@@ -0,0 +1,61 @@
+# Metrics Selector
+
+The **metric_selector** processor allows you to select metrics to include or exclude (similar to the `grep` filter for logs).
+
+## Configuration Parameters <a id="config"></a>
+
+The native processor plugin supports the following configuration parameters:
+
+| Key         | Description | Default |
+| :---------- | :--- | :--- |
+| Metric\_Name | Keep metrics in which the metric of name matches with the actual name or the regular expression. | |
+| Context | Specify matching context. Currently, metric_name is only supported. | `Metrics_Name` |
+| Action | Specify the action for specified metrics. INCLUDE and EXCLUDE are allowed. | |
+| Operation\_Type | Specify the operation type of action for metrics payloads. PREFIX and SUBSTRING are allowed. | |
+
+## Configuration Examples <a id="config_example"></a>
+
+Here is a basic configuration example.
+
+{% tabs %}
+{% tab title="fluent-bit.yaml" %}
+```yaml
+service:
+  flush: 5
+  daemon: off
+  log_level: info
+
+pipeline:
+  inputs:
+    - name: fluentbit_metrics
+      tag: fluentbit.metrics
+      scrape_interval: 10
+
+      processors:
+        metrics:
+          - name: metrics_selector
+            metric_name: /storage/
+            action: include
+          - name: metrics_selector
+            metric_name: /fs/
+            action: exclude
+
+          - name: labels
+            delete: name
+
+
+  outputs:
+    - name: stdout
+      match: '*'
+```
+{% endtab %}
+{% endtabs %}
+
+
+All processors are only valid with the YAML configuration format. 
+Processor configuration should be located under the relevant input or output plugin configuration.
+
+Metric\_Name parameter will translate the strings which is quoted with backslashes `/.../` as Regular expressions.
+Without them, users need to specify Operation\_Type whether prefix matching or substring matching.
+The default operation is prefix matching.
+For example, `/chunks/` will be translated as a regular expression.