[logstash] add headless service for statefulset (#695)

This commit add a mandatory headless service for Logstash statefulset.

Headless service is required for Statefulsets.
While Helm 2 allowed to deploy Statefulsets without a serviceName, Helm 3 enforce this requirement and fails if serviceName is missing.

Note: Statefulsets don't accept serviceName field update during release upgrades. This change is therefore considered as a breaking change and will require using `helm upgrade --force` for upgrades.

logstash/templates/service-headless.yaml

@@ -0,0 +1,23 @@
+---
+kind: Service
+apiVersion: v1
+metadata:
+  name: "{{ template "logstash.fullname" . }}-headless"
+  labels:
+    app: "{{ template "logstash.fullname" . }}"
+    chart: "{{ .Chart.Name }}"
+    heritage: {{ .Release.Service | quote }}
+    release: {{ .Release.Name | quote }}
+{{- if .Values.labels }}
+{{ toYaml .Values.labels | indent 4 }}
+{{- end }}
+spec:
+  clusterIP: None
+  selector:
+    app: "{{ template "logstash.fullname" . }}"
+  ports:
+  - name: http
+    port: {{ .Values.httpPort }}
+{{- if .Values.extraPorts }}
+{{- toYaml .Values.extraPorts | nindent 2 }}
+{{- end }}

logstash/templates/statefulset.yaml

@@ -12,9 +12,7 @@ metadata:
     {{ $key }}: {{ $value | quote }}
     {{- end }}
 spec:
-  {{- if .Values.service }}
-  serviceName: {{ template "logstash.fullname" . }}
-  {{- end }}
+  serviceName: {{ template "logstash.fullname" . }}-headless
   selector:
     matchLabels:
       app: "{{ template "logstash.fullname" . }}"
@@ -151,7 +149,7 @@ spec:
         - name: http
           containerPort: {{ .Values.httpPort }}
       {{- if .Values.extraPorts }}
-        {{- toYaml .Values.extraPorts | nindent 8 }}  
+        {{- toYaml .Values.extraPorts | nindent 8 }}
       {{- end }}
         resources:
 {{ toYaml .Values.resources | indent 10 }}

logstash/tests/logstash_test.py

@@ -78,8 +78,9 @@ def test_defaults():
     )
 
     # Service
-    assert "serviceName" not in r["statefulset"][name]["spec"]
-    assert "service" not in r
+    assert r["statefulset"][name]["spec"]["serviceName"] == name + "-headless"
+    assert name + "-headless" in r["service"]
+    assert r["service"][name + "-headless"]["spec"]["ports"][0]["port"] == 9600
 
     # Other
     assert r["statefulset"][name]["spec"]["template"]["spec"]["securityContext"] == {