[meta] add support for k8s 1.16

elasticsearch/examples/upgrade/README.md

@@ -11,14 +11,17 @@ not compatible with K8S >= 1.16)
 
 ## Usage
 
-Running `make install` command will do first install and 7.7.0 upgrade
+Running `make install` command will do first install and 7.7.0 upgrade.
+
+Note: [jq][] is a requirement for this make target.
 
 
 ## Testing
 
-You can also run [goss integration tests][] using `make test`
+You can also run [goss integration tests][] using `make test`.
 
 
 [7.0.0-alpha1]: https://github.com/elastic/helm-charts/releases/tag/7.0.0-alpha1
 [7.4.0]: https://github.com/elastic/helm-charts/releases/tag/7.4.0
 [goss integration tests]: https://github.com/elastic/helm-charts/tree/master/elasticsearch/examples/upgrade/test/goss.yaml
+[jq]: https://stedolan.github.io/jq/

elasticsearch/examples/upgrade/scripts/upgrade.sh

@@ -1,15 +1,15 @@
 #!/usr/bin/env bash
 
-set -exo pipefail
+set -euo pipefail
 
 usage() {
   cat <<-EOF
 	USAGE:
-	  $0 [--release <release-name>] [--from <elasticsearch-version>] --to <elasticsearch-version>
+	  $0 [--release <release-name>] [--from <elasticsearch-version>]
 	  $0 --help
 
 	OPTIONS:
-    --release <release-name>
+	  --release <release-name>
 	    Name of the Helm release to install
 	  --from <elasticsearch-version>
 	    Elasticsearch version to use for first install
@@ -43,10 +43,17 @@ do
   esac
 done
 
+if ! command -v jq > /dev/null
+then
+  echo 'jq is required to use this script'
+  echo 'please check https://stedolan.github.io/jq/download/ to install it'
+  exit 1
+fi
+
 # Elasticsearch chart < 7.4.0 are not compatible with K8S >= 1.16)
 if [[ -z $FROM ]]
 then
-  KUBE_MINOR_VERSION=$(kubectl version --client -o yaml | grep minor | sed 's/[^0-9]*//g')
+  KUBE_MINOR_VERSION=$(kubectl version -o json | jq -c '.serverVersion.minor' | sed 's/[^0-9]*//g')
 
   if [ "$KUBE_MINOR_VERSION" -lt 16 ]
   then