Scrape function Pods

As part of openfaas/docs#173 this
patch gives Prometheus a directive and permissions to scrape
Pods in the openfaas-fn namespace, so that they can be used
in HPAv2.

The Prometheus kubernetes_sd_configs is updated to add the
default function namespace into scope for scraping.

Longer term, a ClusterRoleBinding will be needed to cover the
"multiple namespaces" use-case, like there is a ClusterRole/
Binding for faas-netes as a non-default option. The
Prometheus scraping may need to look for namespaces or Pods
that match an annotation, or have a wildcard scan across
all namespaces, instead of the two it has after this PR
is merged.

@LucasRoesler also raised Push Gateways as an option for
future consideration.

The watchdog has built-in metrics on port 8082, and will be
scraped if the Prometheus scrape annotation is added.

Custom HTTP servers are also supported, and you can serve on
port 8080, or specify an alternative port via annotations.

For instance:
prometheus.io/scrape: true
prometheus.io/port: 8080

Issue #621 allows the scrape annotation to be overridden, which
current cannot due a default set in the controller.

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

chart/openfaas/Chart.yaml

@@ -1,7 +1,7 @@
 apiVersion: v1
 description: Enable Kubernetes as a backend for OpenFaaS (Functions as a Service)
 name: openfaas
-version: 5.7.1
+version: 5.7.2
 sources:
 - https://github.com/openfaas/faas
 - https://github.com/openfaas/faas-netes

chart/openfaas/templates/prometheus-cfg.yaml

@@ -37,6 +37,7 @@ data:
             namespaces:
               names:
                 - {{ .Release.Namespace }}
+                - {{  $functionNs }}
         relabel_configs:
         - action: labelmap
           regex: __meta_kubernetes_pod_label_(.+)

chart/openfaas/templates/prometheus-rbac.yaml

@@ -14,10 +14,9 @@ metadata:
     release: {{ .Release.Name }}
 ---
 apiVersion: rbac.authorization.k8s.io/v1
-kind: Role
+kind: ClusterRole
 metadata:
   name: {{ .Release.Name }}-prometheus
-  namespace: {{ .Release.Namespace | quote }}
   labels:
     app: {{ template "openfaas.name" . }}
     chart: {{ .Chart.Name }}-{{ .Chart.Version }}
@@ -45,7 +44,27 @@ metadata:
     release: {{ .Release.Name }}
 roleRef:
   apiGroup: rbac.authorization.k8s.io
-  kind: Role
+  kind: ClusterRole
+  name: {{ .Release.Name }}-prometheus
+subjects:
+- kind: ServiceAccount
+  name: {{ .Release.Name }}-prometheus
+  namespace: {{ .Release.Namespace | quote }}
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: RoleBinding
+metadata:
+  name: {{ .Release.Name }}-prometheus
+  namespace: {{ $functionNs | quote }}
+  labels:
+    app: {{ template "openfaas.name" . }}
+    chart: {{ .Chart.Name }}-{{ .Chart.Version }}
+    component: prometheus
+    heritage: {{ .Release.Service }}
+    release: {{ .Release.Name }}
+roleRef:
+  apiGroup: rbac.authorization.k8s.io
+  kind: ClusterRole
   name: {{ .Release.Name }}-prometheus
 subjects:
 - kind: ServiceAccount

contrib/create-static-manifest.sh

@@ -25,7 +25,7 @@ for filepath in $TEMPLATE_FILE; do
     filename=$(basename $filepath)
     outputname="${filename%%.*}.yml"
     # Use helm to generate the yaml and then use sed to remove the helm specific lables/annotations.
-    helm template "$CHART_DIR" --name=faas --namespace="$NAMEPSPACE" --set "functionNamespace=$FUNCTIONNAMESPACE" -x templates/$filename --values="$VALUESNAME" \
+    helm template "$CHART_DIR" --name=openfaas --namespace="$NAMEPSPACE" --set "functionNamespace=$FUNCTIONNAMESPACE" -x templates/$filename --values="$VALUESNAME" \
         | sed -E '/(chart:)|(release:)|(heritage:)/d' \
         | sed -E '/# Source:/d' \
         | sed -E '/^$/d' \