Using another query in alerts description

[Yashar Nesabian]

Hi

I have an alert which fires when a CPU temperature is in the critical state:

ipmi_temperature_state{id="21",name="02-CPU 1"} == 2

And I have another metric which shows the temperature of this CPU:

ipmi_temperature_celsius{id="21",name="02-CPU 1"}

I wonder if it is possible to print the output of the second metric when the alert fires?

[Brian Candler]

Since the labels are the same, this is straightforward:

expr: ipmi_temperature_celsius and (ipmi_temperature_state == 2)

The $value of the alert is now ipmi_temperature_celsius - but the value will only be passed through if there is a matching RHS timeseries (with any value, but in this case it's filtered so that the RHS timeseries is filtered out unless the value is 2).  

PromQL expressions with comparison operators are like filters.  For example:

expr: ipmi_temperature_celsius > 40

is not a true/false, but rather it passes through timeseries where the value is > 40, and excludes timeseries where the value is <= 40.

See:

https://prometheus.io/docs/prometheus/latest/querying/operators/#comparison-binary-operators

https://prometheus.io/docs/prometheus/latest/querying/operators/#logical-set-binary-operators

[Yashar Nesabian]

Thanks Brian, this solved my problem

[Julien Pivotto]

Yes:


Simple answer:

Use:

ipmi_temperature_celsius and (ipmi_temperature_state == 2)

as alerting query

and use "{{$value}}"

Complex answer (please don't use):

{{ $q := printf "ipmi_temperature_celsius{id='%s',name='%s'}" $labels.id $labels.name}}·
{{ with query $q }}
{{ . | first | value | humanize }}
{{ end }}

https://prometheus.io/docs/prometheus/latest/configuration/template_examples/

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Julien Pivotto
@roidelapluie