MNAIO: Enable saving and re-using file-based backing images

Being able to save the images and re-use them on other hosts
is extremely useful to cut down deployment time. This patch
allows an MNAIO setup to be setup using a file-based backing
store, then have those saved and re-used on the same host or
on other hosts.

Change-Id: I491d04fb94352e37312891a9b9bd58093fdd00cf

multi-node-aio/README.rst

@@ -258,3 +258,22 @@ backing store) for the VM's, then set the following option before executing
 
     export MNAIO_ANSIBLE_PARAMETERS="-e default_vm_disk_mode=file"
     ./build.sh
+
+If you wish to save the current file-based images in order to implement a
+thin-provisioned set of VM's which can be saved and re-used, then use the
+``save-vms.yml`` playbook. This will stop the VM's and save the files to
+``/var/lib/libvirt/images/*-base.img``. Re-executing the ``deploy-vms.yml``
+playbook afterwards will rebuild the VMs from those images.
+
+.. code-block:: bash
+
+    ansible-playbook -i playbooks/inventory playbooks/save-vms.yml
+    ansible-playbook -i playbooks/inventory -e default_vm_disk_mode=file playbooks/deploy-vms.yml
+
+To disable this default functionality when re-running ``build.sh`` set the
+build not to use the snapshots as follows.
+
+.. code-block:: bash
+
+    export MNAIO_ANSIBLE_PARAMETERS="-e default_vm_disk_mode=file -e vm_use_snapshot=no"
+    ./build.sh

multi-node-aio/playbooks/deploy-vms.yml

@@ -67,13 +67,34 @@
         - default_vm_disk_mode | default('lvm') == "lvm"
       with_items: "{{ groups['pxe_servers'] }}"
 
-    - name: Create VM Disk Image
-      command: |
-        qemu-img create -f qcow2 /var/lib/libvirt/images/{{ hostvars[item]['server_hostname'] }}.img {{ default_vm_storage }}m
+    - name: Setup file-based disk images
       when:
-        - hostvars[item]['server_vm'] | default(false) | bool
         - default_vm_disk_mode | default('lvm') == "file"
-      with_items: "{{ groups['pxe_servers'] }}"
+      block:
+        - name: Find existing base image files
+          find:
+            paths: /var/lib/libvirt/images
+            patterns: '*-base.img'
+          register: _base_images
+
+        - name: Set vm_use_snapshot if it's not defined
+          set_fact:
+            vm_use_snapshot: "{{ _base_images['matched'] > 0 }}"
+          when:
+            - vm_use_snapshot is not defined
+
+        - name: Create VM Disk Image
+          command: >-
+            qemu-img create
+            -f qcow2
+            {% if vm_use_snapshot | bool %}
+            -b /var/lib/libvirt/images/{{ hostvars[item]['server_hostname'] }}-base.img
+            {% endif %}
+            /var/lib/libvirt/images/{{ hostvars[item]['server_hostname'] }}.img
+            {{ default_vm_storage }}m
+          when:
+            - hostvars[item]['server_vm'] | default(false) | bool
+          with_items: "{{ groups['pxe_servers'] }}"
 
     - name: Create the VM template
       template:

multi-node-aio/playbooks/save-vms.yml

@@ -0,0 +1,48 @@
+---
+# Copyright 2018, Rackspace US, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in witing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+- name: Save VM disk images for re-use
+  hosts: vm_hosts
+  gather_facts: "{{ gather_facts | default(true) }}"
+  environment: "{{ deployment_environment_variables | default({}) }}"
+  tags:
+    - save-vms
+  tasks:
+    - name: Gather variables for each operating system
+      include_vars: "{{ item }}"
+      with_first_found:
+        - "{{ playbook_dir }}/vars/{{ ansible_distribution | lower }}-{{ ansible_distribution_version | lower }}.yml"
+        - "{{ playbook_dir }}/vars/{{ ansible_distribution | lower }}-{{ ansible_distribution_major_version | lower }}.yml"
+        - "{{ playbook_dir }}/vars/{{ ansible_os_family | lower }}-{{ ansible_distribution_major_version | lower }}.yml"
+        - "{{ playbook_dir }}/vars/{{ ansible_distribution | lower }}.yml"
+        - "{{ playbook_dir }}/vars/{{ ansible_os_family | lower }}.yml"
+      tags:
+        - always
+
+    - name: Stop running VMs
+      command: "virsh destroy {{ hostvars[item]['server_hostname'] }}"
+      failed_when: false
+      when:
+        - hostvars[item]['server_vm'] | default(false) | bool
+      with_items: "{{ groups['pxe_servers'] }}"
+
+    - name: Save VM Disk Image
+      command: >-
+        mv
+        /var/lib/libvirt/images/{{ hostvars[item]['server_hostname'] }}.img
+        /var/lib/libvirt/images/{{ hostvars[item]['server_hostname'] }}-base.img
+      when:
+        - hostvars[item]['server_vm'] | default(false) | bool
+      with_items: "{{ groups['pxe_servers'] }}"