Dont do tasks with worker_ip_addresses when its undefined

research-cloud-plugin.yml

@@ -23,21 +23,23 @@
         name: jumphost
         hostname: localhost
 
-    - name: Create group workers with workers' IPs
-      add_host:
-        name: "{{ item }}"
-        groups: workers
-        ansible_user: ubuntu
-        ansible_connection: ssh
-        ansible_ssh_private_key_file: ~/.ssh/id_rsa
-        ansible_become: yes
-      loop: '{{ worker_ip_addresses }}'
-
-    - name: Scan for worker keys.
-      shell:
-        cmd: ssh-keyscan {{ item }}
-      register: ssh_scan
-      loop: '{{ worker_ip_addresses }}'
+    - name: SSH to workers configuration
+      when: worker_ip_addresses
+      block:
+        - name: Create group workers with workers' IPs
+          add_host:
+            name: "{{ item }}"
+            groups: workers
+            ansible_user: ubuntu
+            ansible_connection: ssh
+            ansible_ssh_private_key_file: ~/.ssh/id_rsa
+            ansible_become: yes
+          loop: '{{ worker_ip_addresses }}'
+        - name: Scan for worker keys.
+          shell:
+            cmd: ssh-keyscan {{ item }}
+          register: ssh_scan
+          loop: '{{ worker_ip_addresses }}'
 
     - name: Write the worker keys to known hosts
       known_hosts: