first draft of alerting usage

Guide-Alerting.md

@@ -1,2 +1,97 @@
-# WIP
+# Prometheus Alerting
 
+## Table of Contents
+
+- [Overview](#overview)
+- [AlertManagerConfig](#AlertManagerConfig)
+- [References](#references)
+
+## Overview
+
+This guide explains how to configure the AlertmanagerConfig CRD to route Prometheus alerts to appropriate receivers.
+
+## AlertManagerConfig
+
+The example below demonstrates configuring an email receiver for alerts.
+
+First, create a Kubernetes Secret containing the SMTP credentials used by the email receiver.
+
+```yaml
+apiVersion: v1
+kind: Secret
+metadata:
+  name: smtp-secret
+type: Opaque
+stringData:
+  password: $ùpèr3Pa$sword
+```
+
+Next, deploy the AlertmanagerConfig resource into the namespace you wish to monitor.
+
+```yaml
+apiVersion: monitoring.coreos.com/v1beta1
+kind: AlertmanagerConfig
+metadata:
+  name: alerts
+spec:
+  receivers:
+    - name: email-receiver
+      emailConfigs:
+        - to: "operations@phoenix-technologies.ch"
+          from: "openshift@phoenix-technologies.ch"
+          smarthost: "smtp.office365.com:587"
+          authUsername: "openshift@phoenix-technologies.ch"
+          authPassword:
+            name: smtp-secret
+            key: password
+          sendResolved: true
+          headers:
+            - key: Subject
+              value: '[{{ .CommonLabels.namespace }}][{{ .Status | toUpper }}{{ if eq .Status "firing" }}:{{ .Alerts.Firing | len }}{{ end }}] {{ .GroupLabels.SortedPairs.Values | join " " }} {{ if gt (len .CommonLabels) (len .GroupLabels) }}({{ with .CommonLabels.Remove .GroupLabels.Names }}{{ .Values | join " " }}{{ end }}){{ end }}'
+
+  inhibitRules:
+    - sourceMatch:
+        - name: severity
+          value: critical
+      targetMatch:
+        - name: severity
+          value: warning
+      equal: ["alertname"]
+
+  route:
+    groupBy:
+      - alertname
+      - severity
+    groupWait: 30s
+    groupInterval: 5m
+    repeatInterval: 12h
+    receiver: email-receiver
+    routes:
+      - matchers:
+          - name: severity
+            value: critical
+            matchType: "="
+        receiver: email-receiver
+        groupWait: 2m
+        groupInterval: 30m
+        repeatInterval: 3h
+      - matchers:
+          - name: severity
+            value: warning
+            matchType: "="
+        receiver: email-receiver
+        groupWait: 5m
+        groupInterval: 1h
+        repeatInterval: 12h
+```
+
+## References
+
+### Official Documentation
+- [AlertManager Official Documentation](https://prometheus.io/docs/alerting/0.26/overview)
+- [AlertManager GitHub Repository](https://github.com/prometheus/alertmanager/tree/v0.26.0)
+
+### Configuration Sections
+- [Inhibition](https://prometheus.io/docs/alerting/0.26/configuration/#inhibition-related-settings)
+- [Receiver](https://prometheus.io/docs/alerting/0.26/configuration/#receiver-integration-settings)
+- [Route](https://prometheus.io/docs/alerting/0.26/configuration/#route-related-settings)