[stable/prometheus] Alertmanager config from Secret (#9317)

* Allowing configuration filename customization.
Eases migration from/to 
https://github.com/coreos/prometheus-operator/tree/master/helm/alertmanager

Signed-off-by: Marcos Estevez <marcos.estevez@ic-consult.com>

* Allows loading configuration from external Secret file.

Signed-off-by: Marcos Estevez <marcos.estevez@ic-consult.com>

* Version bump and documentation

Signed-off-by: Marcos Estevez <marcos.estevez@ic-consult.com>

* Typo fix

Signed-off-by: Marcos Estevez <marcos.estevez@ic-consult.com>

stable/prometheus/Chart.yaml

@@ -1,5 +1,5 @@
 name: prometheus
-version: 8.4.2
+version: 8.4.3
 appVersion: 2.6.0
 description: Prometheus is a monitoring system and time series database.
 home: https://prometheus.io/

stable/prometheus/README.md

@@ -101,6 +101,8 @@ Parameter | Description | Default
 `alertmanager.baseURL` | The external url at which the server can be accessed | `/`
 `alertmanager.extraArgs` | Additional alertmanager container arguments | `{}`
 `alertmanager.configMapOverrideName` | Prometheus alertmanager ConfigMap override where full-name is `{{.Release.Name}}-{{.Values.alertmanager.configMapOverrideName}}` and setting this value will prevent the default alertmanager ConfigMap from being generated | `""`
+`alertmanager.configFromSecret` | The name of a secret in the same kubernetes namespace which contains the Alertmanager config, setting this value will prevent the default alertmanager ConfigMap from being generated | `""`
+`alertmanager.configFileName` | The configuration file name to be loaded to alertmanager. Must match the key within configuration loaded from ConfigMap/Secret. | `alertmanager.yml`
 `alertmanager.ingress.enabled` | If true, alertmanager Ingress will be created | `false`
 `alertmanager.ingress.annotations` | alertmanager Ingress annotations | `{}`
 `alertmanager.ingress.extraLabels` | alertmanager Ingress additional labels | `{}`

stable/prometheus/templates/alertmanager-configmap.yaml

@@ -1,4 +1,4 @@
-{{- if and .Values.alertmanager.enabled (empty .Values.alertmanager.configMapOverrideName) -}}
+{{- if and .Values.alertmanager.enabled (and (empty .Values.alertmanager.configMapOverrideName) (empty .Values.alertmanager.configFromSecret)) -}}
 apiVersion: v1
 kind: ConfigMap
 metadata:

stable/prometheus/templates/alertmanager-deployment.yaml

@@ -49,7 +49,7 @@ spec:
                   apiVersion: v1
                   fieldPath: status.podIP
           args:
-            - --config.file=/etc/config/alertmanager.yml
+            - --config.file=/etc/config/{{ .Values.alertmanager.configFileName }}
             - --storage.path={{ .Values.alertmanager.persistentVolume.mountPath }}
             - --cluster.advertise-address=$(POD_IP):6783
           {{- range $key, $value := .Values.alertmanager.extraArgs }}
@@ -110,8 +110,13 @@ spec:
     {{- end }}
       volumes:
         - name: config-volume
+          {{- if empty .Values.alertmanager.configFromSecret }}
           configMap:
             name: {{ if .Values.alertmanager.configMapOverrideName }}{{ .Release.Name }}-{{ .Values.alertmanager.configMapOverrideName }}{{- else }}{{ template "prometheus.alertmanager.fullname" . }}{{- end }}
+          {{- else }}
+          secret:
+            secretName: {{ .Values.alertmanager.configFromSecret }}
+          {{- end }}
         - name: storage-volume
         {{- if .Values.alertmanager.persistentVolume.enabled }}
           persistentVolumeClaim:

stable/prometheus/values.yaml

@@ -67,6 +67,17 @@ alertmanager:
   ##
   configMapOverrideName: ""
 
+  ## The name of a secret in the same kubernetes namespace which contains the Alertmanager config
+  ## Defining configFromSecret will cause templates/alertmanager-configmap.yaml
+  ## to NOT generate a ConfigMap resource
+  ##
+  configFromSecret: ""
+
+  ## The configuration file name to be loaded to alertmanager
+  ## Must match the key within configuration loaded from ConfigMap/Secret
+  ##
+  configFileName: alertmanager.yml
+
   ingress:
     ## If true, alertmanager Ingress will be created
     ##