apiVersion shouldn't be hardcoded (#5060)

* apiVersion shouldn't be hardcoded

* updated chart version

* fixed semver comparison

incubator/elasticsearch-curator/Chart.yaml

@@ -2,7 +2,7 @@ apiVersion: v1
 appVersion: "5.4.1"
 description: A Helm chart for Elasticseach Curator
 name: elasticsearch-curator
-version: 0.1.0
+version: 0.1.1
 home: https://github.com/elastic/curator
 keywords:
 - curator

incubator/elasticsearch-curator/README.md

@@ -6,6 +6,9 @@ This directory contains a Kubernetes chart to deploy the [Elasticsearch Curator]
 
 * Elasticsearch
 
+* The `elasticsearch-curator` cron job requires [K8s CronJob](https://kubernetes.io/docs/concepts/workloads/controllers/cron-jobs/) support: 
+    > You need a working Kubernetes cluster at version >= 1.8 (for CronJob). For previous versions of cluster (< 1.8) you need to explicitly enable `batch/v2alpha1` API by passing `--runtime-config=batch/v2alpha1=true` to the API server ([see Turn on or off an API version for your cluster for more](https://kubernetes.io/docs/admin/cluster-management/#turn-on-or-off-an-api-version-for-your-cluster)).
+
 ## Chart Details
 
 This chart will do the following:

incubator/elasticsearch-curator/templates/_helpers.tpl

@@ -1,5 +1,16 @@
 {{/* vim: set filetype=mustache: */}}
 
+{{/*
+Return the appropriate apiVersion for cronjob APIs.
+*/}}
+{{- define "cronjob.apiVersion" -}}
+{{- if semverCompare "< 1.8-0" .Capabilities.KubeVersion.GitVersion -}}
+{{- print "batch/v2alpha1" }}
+{{- else if semverCompare ">=1.8-0" .Capabilities.KubeVersion.GitVersion -}}
+{{- print "batch/v1beta1" }}
+{{- end -}}
+{{- end -}}
+
 {{/*
 Expand the name of the chart.
 */}}

incubator/elasticsearch-curator/templates/cronjob.yaml

@@ -1,4 +1,4 @@
-apiVersion: batch/v1beta1
+apiVersion: {{ template "cronjob.apiVersion" . }}
 kind: CronJob
 metadata:
   name: {{ template "elasticsearch-curator.fullname" . }}
@@ -19,7 +19,7 @@ spec:
         spec:
           volumes:
             - name: config-volume
-              configMap: 
+              configMap:
                 name: curator-config
           restartPolicy: Never
           containers: