## Alert rules with two or more queries or expressions
In the case where an alert rule has two or more queries, or uses reduce and math expressions, it is possible to template
the reduced result of each query and expression with the `$values` variable. This variable holds the labels and value of
each reduced query, and the results of any math expressions. However, it does not hold the samples for each query.
For example, suppose you have the following alert rule:
{{<figuresrc="/static/img/docs/alerting/unified/grafana-alerting-histogram-quantile.png"class="docs-image--no-shadow"caption="An alert rule that uses histogram_quantile to compute 95th percentile">}}
Should this rule create an alert instance `$values` will hold the result of the reduce expression `B` and the math
expression `C`. It will not hold the results returned by query `A` because query `A` does not return a single value
but rather a series of values over time.
If we were to write a summary annotation such as:
```
{{ $labels.instance }} has a 95th percentile request latency above 1s: {{ $value }})
```
We would find that because the condition of the alert, the math expression `C` must be a boolean comparison, it must
return either a `0` or a `1`. What we want instead is the 95th percentile from the reduce expression `B`:
```
{{ $labels.instance }} has a 95th percentile request latency above 1s: {{ $values.B }})
```
We can also show the labels of `B`, however since this alert rule has just one query the labels of `B` are equivalent to
`$labels`:
```
{{ values.B.Labels.instance }} has a 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
`{{ $values.B }}` will be nil. To ensure that annotations and labels can still be templated even when a query returns
no data, we can use an if statement to check for `$values.B`:
```
{{ if $values.B }}{{ $labels.instance }} has a 95th percentile request latency above 1s: {{ $values.B }}){{ end }}
```
## Classic conditions
If the rule uses a classic condition instead of a reduce and math expresison, then `$values` contains the combination
of the `refID` and position of the condition. For example, `{{ $values.A0 }}` and `{{ $values.A1 }}`.
## Variables
The following template variables are available when expanding annotations and labels.
The following template variables are available when expanding annotations and labels.
| $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]({{< relref "../../alerting-rules/create-grafana-managed-rule/#single-and-multi-dimensional-rule" >}}). |
| $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]({{< relref "../../alerting-rules/create-grafana-managed-rule/#single-and-multi-dimensional-rule" >}}). |
| $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. If the rule uses classic conditions, then a combination of the `refID` and position of the condition is used. For example, `{{ $values.A0.Value }}` or `{{ $values.A1.Value }}`. If a value can return no data then it is recommended to use either `{{ $values.A }}` where the missing value will show `<no value>` or an if statement to check if `A` exists when using `{{ $values.A.Labels }}` and `{{ $values.A.Value }}`. For example, `{{ if $values.A }}{{ $values.A.Value }}{{ end }}`. |
| $values | The values of all reduce and math expressions that were evaluated for this alert rule. For example, `{{ $values.A }}`, `{{ $values.A.Labels }}` and `{{ $values.A.Value }}` where `A` is the `refID` of the reduce or math expression. If the rule uses a classic condition instead of a reduce and math expresison, then `$values` contains the combination of the `refID` and position of the condition. |
| $value | The value string of the alert instance. For example, `[ var='A' labels={instance=foo} value=10 ]`. |
| $value | The value string of the alert instance. For example, `[ var='A' labels={instance=foo} value=10 ]`. |
George Robinson
3 years ago
committed by