check if the storage backend is set to etcd3 before upgrading to 3.7

playbooks/common/openshift-cluster/upgrades/pre/verify_etcd3_backend.yml

@@ -0,0 +1,22 @@
+---
+- name: Verify all masters has etcd3 storage backend set
+  hosts: oo_masters_to_config
+  gather_facts: no
+  roles:
+  - lib_utils
+  tasks:
+  - name: Read master storage backend setting
+    yedit:
+      state: list
+      src: /etc/origin/master/master-config.yaml
+      key: kubernetesMasterConfig.apiServerArguments.storage-backend
+    register: _storage_backend
+
+  - fail:
+      msg: "Storage backend in /etc/origin/master/master-config.yaml must be set to 'etcd3' before the upgrade can continue"
+    when:
+    # assuming the master-config.yml is properly configured, i.e. the value is a list
+    - _storage_backend.result | default([], true) | length == 0 or _storage_backend.result[0] != "etcd3"
+
+  - debug:
+      msg: "Storage backend is set to etcd3"

playbooks/common/openshift-cluster/upgrades/v3_7/upgrade_control_plane.yml

@@ -29,6 +29,10 @@
   tags:
   - pre_upgrade
 
+- include: ../pre/verify_etcd3_backend.yml
+  tags:
+  - pre_upgrade
+
 - name: Update repos on control plane hosts
   hosts: oo_masters_to_config:oo_etcd_to_config:oo_lb_to_config
   tags: