Update loki.relabel to logs instead of metrics (#4422)

docs/sources/flow/reference/components/loki.relabel.md

@@ -60,7 +60,7 @@ rule | [rule][] | Relabeling rules to apply to received log entries. | no
 
 ### rule block
 
-{{< docs/shared lookup="flow/reference/components/rule-block.md" source="agent" >}}
+{{< docs/shared lookup="flow/reference/components/rule-block-logs.md" source="agent" >}}
 
 ## Exported fields
 

docs/sources/shared/flow/reference/components/rule-block-logs.md

@@ -0,0 +1,39 @@
+---
+aliases:
+- /docs/agent/shared/flow/reference/components/rule-block/
+headless: true
+---
+
+The `rule` block contains the definition of any relabeling rules that can be
+applied to an input log. If more than one `rule` block is defined, the
+transformations are applied in top-down order.
+
+The following arguments can be used to configure a `rule`. All arguments are
+optional. Omitted fields take their default values.
+
+Name | Type | Description | Default | Required
+---- | ---- | ----------- | ------- | --------
+`source_labels` | `list(string)` | The list of labels whose values are to be selected. Their content is concatenated using the `separator` and matched against `regex`. | | no
+`separator`     | `string`       | The separator used to concatenate the values present in `source_labels`. | ; | no
+`regex`         | `string`       | A valid RE2 expression with support for parenthesized capture groups. Used to match the extracted value from the combination of the `source_label` and `separator` fields or filter labels during the `labelkeep/labeldrop/labelmap` actions. | `(.*)` | no
+`modulus`       | `uint`         | A positive integer used to calculate the modulus of the hashed source label values. | | no
+`target_label`  | `string`       | Label to which the resulting value will be written to. | | no
+`replacement`   | `string`       | The value against which a regex replace is performed, if the regex matches the extracted value. Supports previously captured groups. | $1 | no
+`action`        | `string`       | The relabeling action to perform. | replace | no
+
+Here's a list of the available actions, along with a brief description of their usage.
+
+* `replace`   - Matches `regex` to the concatenated labels. If there's a match, it replaces the content of the `target_label` using the contents of the `replacement` field.
+* `keep`      - Keeps logs where `regex` matches the string extracted using the `source_labels` and `separator`.
+* `drop`      - Drops logs where `regex` matches the string extracted using the `source_labels` and `separator`.
+* `hashmod`   - Hashes the concatenated labels, calculates its modulo `modulus` and writes the result to the `target_label`.
+* `labelmap`  - Matches `regex` against all label names. Any labels that match are renamed according to the contents of the `replacement` field.
+* `labeldrop` - Matches `regex` against all label names. Any labels that match are removed from the logs's label set.
+* `labelkeep` - Matches `regex` against all label names. Any labels that don't match are removed from the logs's label set.
+* `keepequal` - Drop targets for which the concatenated `source_labels` do not match `target_label`.
+* `dropequal` - Drop targets for which the concatenated `source_labels` do match `target_label`.
+* `lowercase` - Sets `target_label` to the lowercase form of the concatenated `source_labels`.
+* `uppercase` - Sets `target_label` to the uppercase form of the concatenated `source_labels`.
+
+Finally, note that the regex capture groups can be referred to using either the
+`$CAPTURE_GROUP_NUMBER` or `${CAPTURE_GROUP_NUMBER}` notation.