DevStack: Use Jinja2 for templating when creating new VMs

This patch is changing the configure-vm.py script to use Jinja2
templating when creating new VMs instead of string interpolation.

Jinja templating allows more complex templating such as conditionals
which will greatly simplify the code for creating Legacy BIOS or UEFI
supported VMs.

Change-Id: Id4a8432923fa71ca8f3f28edd1235d3a318c3e95
Partial-Bug: #1625616

devstack/tools/ironic/scripts/configure-vm.py

@@ -16,6 +16,7 @@
 import argparse
 import os.path
 
+import jinja2
 import libvirt
 
 templatedir = os.path.join(os.path.dirname(os.path.dirname(__file__)),
@@ -80,8 +81,10 @@ def main():
     parser.add_argument('--disk-format', default='qcow2',
                         help='Disk format to use.')
     args = parser.parse_args()
-    with open(templatedir + '/vm.xml', 'rb') as f:
+
-        source_template = f.read()
+    env = jinja2.Environment(loader=jinja2.FileSystemLoader(templatedir))
+    template = env.get_template('vm.xml')
+
     params = {
         'name': args.name,
         'imagefile': args.image,
@@ -108,7 +111,7 @@ def main():
         params['console'] = CONSOLE_LOG % {'console_log': args.console_log}
     else:
         params['console'] = CONSOLE_PTY
-    libvirt_template = source_template % params
+    libvirt_template = template.render(**params)
     conn = libvirt.open("qemu:///system")
 
     a = conn.defineXML(libvirt_template)

devstack/tools/ironic/templates/vm.xml

@@ -1,10 +1,10 @@
-<domain type='%(engine)s'>
+<domain type='{{ engine }}'>
-  <name>%(name)s</name>
+  <name>{{ name }}</name>
-  <memory unit='KiB'>%(memory)s</memory>
+  <memory unit='KiB'>{{ memory }}</memory>
-  <vcpu>%(cpus)s</vcpu>
+  <vcpu>{{ cpus }}</vcpu>
   <os>
-    <type arch='%(arch)s' machine='pc-1.0'>hvm</type>
+    <type arch='{{ arch }}' machine='pc-1.0'>hvm</type>
-    <boot dev='%(bootdev)s'/>
+    <boot dev='{{ bootdev }}'/>
     <bootmenu enable='no'/>
     <bios useserial='yes'/>
   </os>
@@ -18,10 +18,10 @@
   <on_reboot>restart</on_reboot>
   <on_crash>restart</on_crash>
   <devices>
-    <emulator>%(emulator)s</emulator>
+    <emulator>{{ emulator }}</emulator>
     <disk type='file' device='disk'>
-      <driver name='qemu' type='%(disk_format)s' cache='writeback'/>
+      <driver name='qemu' type='{{ disk_format }}' cache='writeback'/>
-      <source file='%(imagefile)s'/>
+      <source file='{{ imagefile }}'/>
       <target dev='vda' bus='virtio'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
     </disk>
@@ -29,8 +29,8 @@
       <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
     </controller>
     <interface type='bridge'>
-      <source bridge='%(bridge)s'/>
+      <source bridge='{{ bridge }}'/>
-      <model type='%(nicdriver)s'/>
+      <model type='{{ nicdriver }}'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
     </interface>
     <input type='mouse' bus='ps2'/>
@@ -39,7 +39,7 @@
       <model type='cirrus' vram='9216' heads='1'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
     </video>
-    %(console)s
+    {{ console }}
     <memballoon model='virtio'>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
     </memballoon>