Annotations and labels for alerting rules
- Annotations
- Labels
  - Template variables
  - Template functions

Annotations and labels for alerting rules

Annotations and labels help customize alert messages so that you can quickly identify the service or application that needs attention.

Annotations

Annotations are key-value pairs that provide additional meta-information about an alert. For example: a description, a summary, and runbook URL. These are displayed in rule and alert details in the UI and can be used in contact type message templates. Annotations can also be templated, for example Instance {{ $labels.instance }} down will have the evaluated instance label value added for every alert this rule produces.

Labels

Labels are key-value pairs that categorize or identify an alert. Labels are used to match alerts in silences or match and groups alerts in notification policies. Labels are also shown in rule or alert details in the UI and can be used in contact type message templates. For example, you can add a severity label, then configure a separate notification policy for each severity. You can also add, for example, a team label and configure notification policies specific to the team or silence all alerts for a particular team. Labels can also be templated like annotations, for example, {{ $labels.namespace }}/{{ $labels.job }} will produce a new rule label that will have the evaluated namespace and job label value added for every alert this rule produces. The rule labels take precedence over the labels produced by the query/condition.

Template variables

The following template variables are available when expanding annotations and labels.

Name	Description
$labels	The labels from the query or condition. For example, `{{ $labels.instance }}` and `{{ $labels.job }}`. This is unavailable when the rule uses a classic condition.
$values	The values of all reduce and math expressions that were evaluated for this alert rule. For example, `{{ $values.A }}`, `{{ $values.A.Labels }}` and `{{ $values.A.Value }}` where `A` is the `refID` of the expression. This is unavailable when the rule uses a classic condition
$value	The value string of the alert instance. For example, `[ var=’A’ labels={instance=foo} value=10 ]`.

Template functions

The following template functions are available when expanding annotations and labels.

Name	Argument	Return	Description
humanize	number or string	string	Converts a number to a more readable format, using metric prefixes.
humanize1024	number or string	string	Like humanize, but uses 1024 as the base rather than 1000.
humanizeDuration	number or string	string	Converts a duration in seconds to a more readable format.
humanizePercentage	number or string	string	Converts a ratio value to a fraction of 100.
humanizeTimestamp	number or string	string	Converts a Unix timestamp in seconds to a more readable format.
title	string	string	strings.Title, capitalises first character of each word.
toUpper	string	string	strings.ToUpper, converts all characters to upper case.
toLower	string	string	strings.ToLower, converts all characters to lower case.
match	pattern, text	boolean	regexp.MatchString Tests for a unanchored regexp match.
reReplaceAll	pattern, replacement, text	string	Regexp.ReplaceAllString Regexp substitution, unanchored.
graphLink	expr	string	Not supported
tableLink	expr	string	Not supported
args	[]interface{}	map[string]interface{}	Converts a list of objects to a map with keys, for example, arg0, arg1. Use this function to pass multiple arguments to templates.
externalURL	nothing	string	Returns a string representing the external URL.
pathPrefix	nothing	string	Returns the path of the external URL.
tmpl	string, []interface{}	nothing	Not supported
safeHtml	string	string	Not supported
query	query string	[]sample	Not supported
first	[]sample	sample	Not supported
label	label, sample	string	Not supported
strvalue	[]sample	string	Not supported
value	sample	float64	Not supported
sortByLabel	label, []samples	[]sample	Not supported