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117 lines
3.5 KiB
Markdown
117 lines
3.5 KiB
Markdown
---
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title: Template examples
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sort_rank: 4
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---
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# Template examples
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Prometheus supports templating in the annotations and labels of alerts,
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as well as in served console pages. Templates have the ability to run
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queries against the local database, iterate over data, use conditionals,
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format data, etc. The Prometheus templating language is based on the [Go
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templating](https://golang.org/pkg/text/template/) system.
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## Simple alert field templates
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```
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alert: InstanceDown
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expr: up == 0
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for: 5m
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labels:
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severity: page
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annotations:
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summary: "Instance {{$labels.instance}} down"
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description: "{{$labels.instance}} of job {{$labels.job}} has been down for more than 5 minutes."
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```
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Alert field templates will be executed during every rule iteration for each
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alert that fires, so keep any queries and templates lightweight. If you have a
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need for more complicated templates for alerts, it is recommended to link to a
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console instead.
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## Simple iteration
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This displays a list of instances, and whether they are up:
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```go
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{{ range query "up" }}
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{{ .Labels.instance }} {{ .Value }}
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{{ end }}
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```
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The special `.` variable contains the value of the current sample for each loop iteration.
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## Display one value
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```go
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{{ with query "some_metric{instance='someinstance'}" }}
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{{ . | first | value | humanize }}
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{{ end }}
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```
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Go and Go's templating language are both strongly typed, so one must check that
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samples were returned to avoid an execution error. For example this could
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happen if a scrape or rule evaluation has not run yet, or a host was down.
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The included `prom_query_drilldown` template handles this, allows for
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formatting of results, and linking to the [expression browser](https://prometheus.io/docs/visualization/browser/).
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## Using console URL parameters
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```go
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{{ with printf "node_memory_MemTotal{job='node',instance='%s'}" .Params.instance | query }}
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{{ . | first | value | humanize1024 }}B
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{{ end }}
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```
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If accessed as `console.html?instance=hostname`, `.Params.instance` will evaluate to `hostname`.
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## Advanced iteration
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```html
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<table>
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{{ range printf "node_network_receive_bytes{job='node',instance='%s',device!='lo'}" .Params.instance | query | sortByLabel "device"}}
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<tr><th colspan=2>{{ .Labels.device }}</th></tr>
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<tr>
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<td>Received</td>
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<td>{{ with printf "rate(node_network_receive_bytes{job='node',instance='%s',device='%s'}[5m])" .Labels.instance .Labels.device | query }}{{ . | first | value | humanize }}B/s{{end}}</td>
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</tr>
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<tr>
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<td>Transmitted</td>
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<td>{{ with printf "rate(node_network_transmit_bytes{job='node',instance='%s',device='%s'}[5m])" .Labels.instance .Labels.device | query }}{{ . | first | value | humanize }}B/s{{end}}</td>
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</tr>{{ end }}
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</table>
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```
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Here we iterate over all network devices and display the network traffic for each.
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As the `range` action does not specify a variable, `.Params.instance` is not
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available inside the loop as `.` is now the loop variable.
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## Defining reusable templates
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Prometheus supports defining templates that can be reused. This is particularly
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powerful when combined with
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[console library](template_reference.md#console-templates) support, allowing
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sharing of templates across consoles.
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```go
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{{/* Define the template */}}
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{{define "myTemplate"}}
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do something
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{{end}}
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{{/* Use the template */}}
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{{template "myTemplate"}}
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```
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Templates are limited to one argument. The `args` function can be used to wrap multiple arguments.
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```go
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{{define "myMultiArgTemplate"}}
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First argument: {{.arg0}}
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Second argument: {{.arg1}}
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{{end}}
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{{template "myMultiArgTemplate" (args 1 2)}}
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```
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