# Create alert with Prometheus

This guide shows you how to create alerts for your application.

## Prerequisites

- Your application serves [metrics](/observability/metrics/how-to/expose.md)

You can define alerts by using Kubernetes resources (`PrometheusRule`), as well as directly in Grafana (GUI based).

You will have a separate Alertmanager for each environment available at `https://alertmanager.<MY-ENV>.dev-nais.cloud.nais.io/`.

## Create PrometheusRule

We use native [Prometheus alert rules](https://prometheus.io/docs/prometheus/latest/configuration/alerting_rules/), and let [Alertmanager](https://prometheus.io/docs/alerting/latest/alertmanager/) handle the notifications.

You can define alerts by creating a `PrometheusRule` resource in your teams namespace.

> **.nais/alert.yaml**
> ```yaml
> apiVersion: monitoring.coreos.com/v1
> kind: PrometheusRule
> metadata:
>   name: <MY-ALERT>
>   namespace: <MY-TEAM>
>   labels:
>     team: <MY-TEAM>
> spec:
>   groups:
>   - name: <MY-ALERT>
>     rules:
>     - alert: InstanceDown
>       expr: kube_deployment_status_replicas_available{namespace="<namespace>", deployment="<application name>"} == 0
>       for: 5m
>       annotations:
>         consequence: Application is unavailable
>         action: "`kubectl describe pod <podname>` -> `kubectl logs <podname>`"
>         summary: |-
>           This is a multi-line summary with
>           linebreaks and everything. Here you can give a more detailed
>           summary of what this alert is about
>       labels:
>         namespace: <MY-TEAM> # required
>         severity: critical
> ```

## Activate the alert

**Automatically**

Add the file to your application repository, alongside `nais.yaml` to deploy with [Nais github action](/build/how-to/build-and-deploy.md).

**Manually**

```bash
kubectl apply -f ./nais/alert.yaml
```

## Verify your alert

You can see the alerts in the Alertmanager at `https://alertmanager.<MY-ENV>.dev-nais.cloud.nais.io/` and the defined rules in [Nais Console](https://console.dev-nais.cloud.nais.io)

## Learn more

[💡 Advanced alerting with Prometheus](/observability/alerting/how-to/prometheus-advanced.md)
[📖 Prometheus alerts reference](/observability/alerting/reference/prometheusrule.md)