AlertingExplore AlertingLabels and annotationsTemplating labels and annotations

Templating labels and annotations

In Grafana it is possible to template labels and annotations just like in Prometheus. Those who have used Prometheus before should be familiar with $labels and $value as these variables contain the labels and value of the alert. You can use the same variables in Grafana to template labels and annotations, even if the alert does not use a Prometheus datasource.

For example, suppose you want to create an alert rule in Grafana that fires when one of your instances is down for more than 5 minutes, and that each alert fired should have a summary annotation to tell you which instance is down:

Instance {{ $labels.instance }} has been down for more than 5 minutes

Labels with dots

If the label contains a dot (full stop or period) in its name then the following will not work:

Instance {{ $labels.instance.name }} has been down for more than 5 minutes

This is because it is attempting to use a non-existing field name in $labels.instance rather than instance.name in $labels. Instead use the index function to print instance.name:

Instance {{ index $labels "instance.name" }} has been down for more than 5 minutes

Use values in labels and annotations

Grafana supports $value when templating labels and annotations. However, while $value in Prometheus is a floating point number contains the value of the expression, $value in Grafana is a string containing the labels and values of all Threshold, Reduce and Maths expressions. It does not contain the value of queries as a single query can return anywhere from 1 to 10,000s of rows or metrics.

This $value variable is called the Value String. If you were to use it in the template of a summary annotation:

{{ $labels.instance }} has an average 95th percentile request latency above 1s: {{ $value }})

you will get the following summary:

http_server has an average 95th percentile request latency above 1s: [ var='B' labels={instance=http_server} value=10 ]

To get just the value of B you can instead use $values:

{{ $labels.instance }} has an average 95th percentile request latency above 1s: {{ $values.B }}

and then you will get this summary:

http_server has an average 95th percentile request latency above 1s: 11

Alert rules with multiple queries, or expressions

If you have an alert rule with multiple queries and expressions, or a single query with a Reduce and Math expression, like in the following example:

An alert rule that uses histogram_quantile to compute 95th percentile
An alert rule that uses histogram_quantile to compute 95th percentile

Then the Value String will not just include the value of the alert condition, but the labels and values of all Threshold, Reduce and Maths expressions.

Example 1: The Value String of an alert rule with a single query and Reduce expression B:

[ var='B' labels={instance=http_server} value=11 ]

Example 2: The Value String of an alert rule with a single query, Reduce expression B and a Math expression C:

[ var='B' labels={instance=http_server} value=11, var='C' labels={instance=http_server} value=1 ]

If you were to write a summary annotation such as:

{{ $labels.instance }} has an average 95th percentile request latency above 1s: {{ $values.C }})

You would find that because the condition of the alert C is a Math expression with a boolean comparison, it must return either a 0 or a 1. What you want instead is the average of the 95th percentile, and you can get this from the reduce expression B:

{{ $labels.instance }} has an average 95th percentile request latency above 1s: {{ $values.B }})

No data and execution errors or timeouts

Should query A return no data then the reduce expression B will also return no data. This means that {{ $values.B }} will be nil. To ensure that labels and annotations can still be templated even when a query returns no data, we can use an if statement to check for this condition:

{{ if $values.B }}{{ $labels.instance }} has a 95th percentile request latency above 1s: {{ $values.B }}){{ end }}

Classic Conditions

If the rule uses Classic Conditions instead of Reduce and Math expressions, then $values contains the combination of the Ref ID and position of the condition. For example, {{ $values.A0 }} and {{ $values.A1 }}.

Reference

Variables

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

NameDescription
$labelsThe labels from the query or condition. For example, {{ $labels.instance }} and {{ $labels.job }}. This is unavailable when the rule uses a classic condition.
$valuesThe 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 reduce or math expression. If the rule uses a classic condition instead of a reduce and math expression, then $values contains the combination of the refID and position of the condition.
$valueThe value string of the alert instance. For example, [ var='A' labels={instance=foo} value=10 ].

Functions

The following functions are also available when expanding labels and annotations:

NameArgument typeReturn typeDescription
humanizenumber or stringstringConverts a number to a more readable format, using metric prefixes.
humanize1024number or stringstringLike humanize, but uses 1024 as the base rather than 1000.
humanizeDurationnumber or stringstringConverts a duration in seconds to a more readable format.
humanizePercentagenumber or stringstringConverts a ratio value to a fraction of 100.
humanizeTimestampnumber or stringstringConverts a Unix timestamp in seconds to a more readable format.
titlestringstringstrings.Title, capitalises first character of each word.
toUpperstringstringstrings.ToUpper, converts all characters to upper case.
toLowerstringstringstrings.ToLower, converts all characters to lower case.
matchpattern, textbooleanregexp.MatchString Tests for a unanchored regexp match.
reReplaceAllpattern, replacement, textstringRegexp.ReplaceAllString Regexp substitution, unanchored.
graphLinkstring - JSON Object with "expr" and "datasource" fieldsstringReturns the path to graphical view in Explore for the given expression and data source.
tableLinkstring- JSON Object with "expr" and "datasource" fieldsstringReturns the path to tabular view in Explore for the given expression and data source.
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.
externalURLnothingstringReturns a string representing the external URL.
pathPrefixnothingstringReturns the path of the external URL.

humanize

Template string { humanize $value }

Input 1234567.0

Expected 1.235M

humanize1024

TemplateString { humanize1024 $value }

Input 1048576.0

Expected 1Mi

humanizeDuration

TemplateString { humanizeDuration $value }

Input 899.99

Expected 14m 59s

humanizePercentage

TemplateString { humanizePercentage $value }

Input 0.1234567

Expected 12.35%

humanizeTimestamp

TemplateString { $value | humanizeTimestamp }

Input 1435065584.128

Expected 2015-06-23 13:19:44.128 +0000 UTC

title

TemplateString { $value | title }

Input aa bb CC

Expected Aa Bb Cc

toUpper

TemplateString { $value | toUpper }

Input aa bb CC

Expected AA BB CC

toLower

TemplateString { $value | toLower }

Input aA bB CC

Expected aa bb cc

match

TemplateString { match "a+" $labels.instance }

Input aa

Expected true

reReplaceAll

TemplateString {{ reReplaceAll "localhost:(.*)" "my.domain:$1" $labels.instance }}

Input localhost:3000

Expected my.domain:3000

TemplateString {{ graphLink "{\"expr\": \"up\", \"datasource\": \"gdev-prometheus\"}" }}

Expected /explore?left=["now-1h","now","gdev-prometheus",{"datasource":"gdev-prometheus","expr":"up","instant":false,"range":true}]

TemplateString {{ tableLink "{\"expr\": \"up\", \"datasource\": \"gdev-prometheus\"}" }}

Expected /explore?left=["now-1h","now","gdev-prometheus",{"datasource":"gdev-prometheus","expr":"up","instant":true,"range":false}]

args

TemplateString {{define "x"}}{{.arg0}} {{.arg1}}{{end}}{{template "x" (args 1 "2")}}

Expected 1 2

externalURL

TemplateString { externalURL }

Expected http://localhost/path/prefix

pathPrefix

TemplateString { pathPrefix }

Expected /path/prefix