Allow broker's service clusterIP customisation (#498)

* Allow broker's service clusterIP customisation

This customisation is useful to configure headless vs non-headless
broker's service. The default is headless broker service, i.e. a
service for which kubernetes  does not allocate an IP
address (https://kubernetes.io/docs/concepts/services-networking/service/#type-clusterip). A
headless service is a very simple type of service that doesn't seem to work well
when pulsar service is exposed by pulsar-proxy via a nodeport.

Addresses #497.

* Address review comments

https://github.com/apache/pulsar-helm-chart/pull/498/files#r1605762934
and https://github.com/apache/pulsar-helm-chart/pull/498/files#r1605763245

* Move doc to Values.broker.service

charts/pulsar/templates/broker-service.yaml

@@ -29,6 +29,7 @@ metadata:
   annotations:
 {{ toYaml .Values.broker.service.annotations | indent 4 }}
 spec:
+  type: ClusterIP
   ports:
   # prometheus needs to access /metrics endpoint
   - name: http
@@ -43,7 +44,7 @@ spec:
   - name: "{{ .Values.tlsPrefix }}pulsarssl"
     port: {{ .Values.broker.ports.pulsarssl }}
   {{- end }}
-  clusterIP: None
+  clusterIP: "{{ .Values.broker.service.clusterIP }}"
   selector:
     {{- include "pulsar.matchLabels" . | nindent 4 }}
     component: {{ .Values.broker.component }}

charts/pulsar/values.yaml

@@ -861,6 +861,12 @@ broker:
   ## templates/broker-service.yaml
   ##
   service:
+    # clusterIP can be one of the three, which determines the type of k8s service deployed for broker
+    # 1. a valid IPv4 address -> non-headless service, let you select the IPv4 address
+    # 2. '' -> non-headless service, k8s picks an IPv4 address
+    # 3. 'None' -> headless
+    # Ref: https://kubernetes.io/docs/concepts/services-networking/service/#type-clusterip
+    clusterIP: "None"
     annotations: {}
   ## Broker PodDisruptionBudget
   ## templates/broker-pdb.yaml