mysql: set hostpath for mysql-data

There is currently an issue with deploying single
pod mysql clusters in which restarting or killing
the pod will result in a crashloopbackoff.
The mysql data is indeed lost and the start script
(thinking the cluster was alive before
due to the grastate configmap) tries to restore
the cluster instead of bootstrapping it.
Due to this, if the mysql pod is killed or restarted
in the CI, we will lose all the mysql data, will not
recover, and this results in a broken environment.

When volume.use_local_path_for_single_pod.enabled value
is set to true, which we will apply on single node/single
pod testing, this patch will deploy a local volume
for mysql at the location specified under
volume.use_local_path_for_single_pod.host_path
The data will be kept intact in case
there is a pod restart, as it can read the data again,
and recover itself.

When it is false, which is the default for non-CI,
nothing changes, and an empty dir is used. This
data WILL be lost upon restart, so it is advised
to use volumes instead for production purposes,
by setting Values.volume.enabled to true.

task: 28729

Change-Id: I6ec0bd1087eb06b92ced7dc56ff5b6a156aad433

mariadb/templates/statefulset.yaml

@@ -239,8 +239,12 @@ spec:
             defaultMode: 0444
         {{- if not .Values.volume.enabled }}
         - name: mysql-data
+        {{- if .Values.volume.use_local_path_for_single_pod_cluster.enabled }}
+          hostPath: {{ .Values.volume.use_local_path_for_single_pod_cluster.host_path }}
+        {{- else }}
           emptyDir: {}
         {{- end }}
+        {{- end }}
 {{- if .Values.volume.enabled }}
   volumeClaimTemplates:
   - metadata:

mariadb/values.yaml

@@ -229,6 +229,11 @@ dependencies:
           service: oslo_db
 
 volume:
+  # this value is used for single pod deployments of mariadb to prevent losing all data
+  # if the pod is restarted
+  use_local_path_for_single_pod:
+    enabled: false
+    host_path: "/tmp/mysql-data"
   chown_on_start: true
   enabled: true
   class_name: general