[stable/concourse] Add Prometheus scrape annotations (#3202)

Avoids needing to specify these in `web.service.annotations`

stable/concourse/Chart.yaml

@@ -1,5 +1,5 @@
 name: concourse
-version: 0.10.7
+version: 0.10.8
 appVersion: 3.6.0
 description: Concourse is a simple and scalable CI system.
 icon: https://avatars1.githubusercontent.com/u/7809479

stable/concourse/README.md

@@ -119,6 +119,8 @@ The following tables lists the configurable parameters of the Concourse chart an
 | `web.ingress.hosts` | Concourse Web Ingress Hostnames | `[]` |
 | `web.ingress.tls` | Concourse Web Ingress TLS configuration | `[]` |
 | `web.additionalAffinities` | Additional affinities to apply to web pods. E.g: node affinity | `nil` |
+| `web.metrics.prometheus.enabled` | Enable Prometheus metrics exporter | `false` |
+| `web.metrics.prometheus.port` | Port for exporting Prometeus metrics | `9391` |
 | `worker.nameOverride` | Override the Concourse Worker components name| `worker` |
 | `worker.replicas` | Number of Concourse Worker replicas | `2` |
 | `worker.minAvailable` | Minimum number of workers available after an eviction | `1` |

stable/concourse/templates/web-svc.yaml

@@ -7,12 +7,14 @@ metadata:
     chart: "{{ .Chart.Name }}-{{ .Chart.Version }}"
     release: "{{ .Release.Name }}"
     heritage: "{{ .Release.Service }}"
-  {{ if .Values.web.service.annotations }}
   annotations:
     {{- range $key, $value := .Values.web.service.annotations }}
     {{ $key }}: {{ $value | quote }}
     {{- end }}
-  {{- end }}
+    {{- if .Values.web.metrics.prometheus.enabled }}
+    prometheus.io/scrape: "true"
+    prometheus.io/port: {{ .Values.web.metrics.prometheus.port | quote }}
+    {{- end }}
 spec:
   type: {{ .Values.web.service.type }}
   ports: