manifests: add Alertmanager manifests and discovery

The latest version of the Prometheus Operator requires Prometheus
>=v1.4.0 for the Alertmanger discovery feature.

manifests/alertmanager/alertmanager-config.yaml

@@ -0,0 +1,18 @@
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: alertmanager-main
+data:
+  alertmanager.yaml: |-
+    global:
+      resolve_timeout: 5m
+    route:
+      group_by: ['job']
+      group_wait: 30s
+      group_interval: 5m
+      repeat_interval: 12h
+      receiver: 'webhook'
+    receivers:
+    - name: 'webhook'
+      webhook_configs:
+      - url: 'http://alertmanagerwh:30500/'

manifests/alertmanager/alertmanager-service.yaml

@@ -0,0 +1,14 @@
+apiVersion: v1
+kind: Service
+metadata:
+  name: alertmanager-main
+spec:
+  type: NodePort
+  ports:
+  - name: web
+    nodePort: 30903
+    port: 9093
+    protocol: TCP
+    targetPort: web
+  selector:
+    alertmanager: alertmanager-main

manifests/alertmanager/alertmanager.yaml

@@ -0,0 +1,9 @@
+apiVersion: "monitoring.coreos.com/v1alpha1"
+kind: "Alertmanager"
+metadata:
+  name: "alertmanager-main"
+  labels:
+    alertmanager: "main"
+spec:
+  replicas: 3
+  version: v0.5.1