// Module included in the following assemblies:
//
// * observability/logging/logging_alerts/custom-logging-alerts.adoc

:_mod-docs-content-type: PROCEDURE
[id="logging-enabling-loki-alerts_{context}"]
= Creating a log-based alerting rule with Loki

The `AlertingRule` CR contains a set of specifications and webhook validation definitions to declare groups of alerting rules for a single `LokiStack` instance. In addition, the webhook validation definition provides support for rule validation conditions:

* If an `AlertingRule` CR includes an invalid `interval` period, it is an invalid alerting rule
* If an `AlertingRule` CR includes an invalid `for` period, it is an invalid alerting rule.
* If an `AlertingRule` CR includes an invalid LogQL `expr`, it is an invalid alerting rule.
* If an `AlertingRule` CR includes two groups with the same name, it is an invalid alerting rule.
* If none of above applies, an alerting rule is considered valid.

[options="header"]
|================================================
| Tenant type    | Valid namespaces for `AlertingRule` CRs
| application    |
| audit          | `openshift-logging`
| infrastructure | `openshift-/\*`, `kube-/\*`, `default`
|================================================

.Prerequisites

* {clo} 5.7 and later
* {product-title} 4.13 and later

.Procedure

. Create an `AlertingRule` custom resource (CR):
+
.Example infrastructure AlertingRule CR
[source,yaml]
----
  apiVersion: loki.grafana.com/v1
  kind: AlertingRule
  metadata:
    name: loki-operator-alerts
    namespace: openshift-operators-redhat <1>
    labels: <2>
      openshift.io/<label_name>: "true"
  spec:
    tenantID: "infrastructure" <3>
    groups:
      - name: LokiOperatorHighReconciliationError
        rules:
          - alert: HighPercentageError
            expr: | <4>
              sum(rate({kubernetes_namespace_name="openshift-operators-redhat", kubernetes_pod_name=~"loki-operator-controller-manager.*"} |= "error" [1m])) by (job)
                /
              sum(rate({kubernetes_namespace_name="openshift-operators-redhat", kubernetes_pod_name=~"loki-operator-controller-manager.*"}[1m])) by (job)
                > 0.01
            for: 10s
            labels:
              severity: critical <5>
            annotations:
              summary: High Loki Operator Reconciliation Errors <6>
              description: High Loki Operator Reconciliation Errors <7>
----
<1> The namespace where this `AlertingRule` CR is created must have a label matching the LokiStack `spec.rules.namespaceSelector` definition.
<2> The `labels` block must match the LokiStack `spec.rules.selector` definition.
<3> `AlertingRule` CRs for `infrastructure` tenants are only supported in the `openshift-\*`, `kube-\*`, or `default` namespaces.
<4> The value for `kubernetes_namespace_name:` must match the value for `metadata.namespace`.
<5> The value of this mandatory field must be `critical`, `warning`, or `info`.
<6> This field is mandatory.
<7> This field is mandatory.
+
.Example application AlertingRule CR
[source,yaml]
----
  apiVersion: loki.grafana.com/v1
  kind: AlertingRule
  metadata:
    name: app-user-workload
    namespace: app-ns <1>
    labels: <2>
      openshift.io/<label_name>: "true"
  spec:
    tenantID: "application"
    groups:
      - name: AppUserWorkloadHighError
        rules:
          - alert:
            expr: | <3>
            sum(rate({kubernetes_namespace_name="app-ns", kubernetes_pod_name=~"podName.*"} |= "error" [1m])) by (job)
            for: 10s
            labels:
              severity: critical <4>
            annotations:
              summary:  <5>
              description:  <6>
----
<1> The namespace where this `AlertingRule` CR is created must have a label matching the LokiStack `spec.rules.namespaceSelector` definition.
<2> The `labels` block must match the LokiStack `spec.rules.selector` definition.
<3> Value for `kubernetes_namespace_name:` must match the value for `metadata.namespace`.
<4> The value of this mandatory field must be `critical`, `warning`, or `info`.
<5> The value of this mandatory field is a summary of the rule.
<6> The value of this mandatory field is a detailed description of the rule.

. Apply the `AlertingRule` CR:
+
[source,terminal]
----
$ oc apply -f <filename>.yaml
----
