rule-block.md

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aliases:
- /docs/agent/shared/flow/reference/components/rule-block/
headless: true

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The rule block contains the definition of any relabeling rules that can be applied to an input metric. 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 metrics where regex matches the string extracted using the source_labels and separator.

• drop - Drops metrics 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 metric's label set.

• labelkeep - Matches regex against all label names. Any labels that don't match are removed from the metric'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.

Finally, note that the regex capture groups can be referred to using either the $CAPTURE_GROUP_NUMBER or ${CAPTURE_GROUP_NUMBER} notation.