Add option to set the machine image cache size

This change adds the option `lxc_host_machine_volume_size` which allows
a deployer to set the image cache size, in gigabytes to something mat
meets their needs. The default value for this option is 16

Change-Id: Ib67da9f203806264c39fc73cc7575ee5acf39e5e
Signed-off-by: Kevin Carter <kevin.carter@rackspace.com>

defaults/main.yml

@@ -28,6 +28,9 @@ lxc_architecture_mapping:
   x86_64: amd64
   ppc64le: ppc64el
 
+# Set the volume size in gigabytes for the machine image caches.
+lxc_host_machine_volume_size: 8
+
 # lxc container rootfs directory and cache path
 lxc_container_directory: "/var/lib/lxc"
 lxc_container_cache_path: "/var/cache/lxc/download"

tasks/lxc_cache_preparation_systemd_new.yml

@@ -23,6 +23,22 @@
   when:
     - lxc_image_cache_refresh | bool
 
+# NOTE(cloudnull): When modern SystemD is running everywhere this can be
+#  collapsed back into the base preparation task file.
+- name : Set volume size
+  shell: |
+    if [[ ! "$(ls -lh /var/lib/machines.raw | awk '{print $5}')" == "{{ lxc_host_machine_volume_size }}G" ]]; then
+      machinectl set-limit {{ lxc_host_machine_volume_size }}G
+      exit 3
+    else
+      exit 0
+    fi
+  register: machines_create
+  changed_when: machines_create.rc == 3
+  failed_when: machines_create.rc not in [0, 3]
+  when:
+    - lxc_image_cache_refresh | bool
+
 - name: Retrieve base image
   command: >-
     machinectl

tasks/lxc_cache_preparation_systemd_old.yml

@@ -18,11 +18,19 @@
 # ==============================================================
 #  In later versions of SystemD this is automatically done for us
 #  by the machinectl cli on first run.
-- name: Create sparse machines file
-  command: "truncate -s 11G /var/lib/machines.raw"
-  args:
-    creates: /var/lib/machines.raw
+- name : Create volume
+  shell: |
+    if [[ ! "$(ls -lh /var/lib/machines.raw | awk '{print $5}')" == "{{ lxc_host_machine_volume_size }}G" ]]; then
+      if [[ ! -f "/var/lib/machines.raw" ]]; then
+        truncate -s {{ lxc_host_machine_volume_size }}G /var/lib/machines.raw
+        exit 3
+      fi
+    fi
   register: machines_create
+  changed_when: machines_create.rc == 3
+  failed_when: machines_create.rc not in [0, 3]
+  when:
+    - lxc_image_cache_refresh | bool
 
 # In later versions of SystemD this is automatically done for us
 #  by the machinectl cli on first run.