[mthaddon,r=gnuoy] Allow for disk_cachemodes to be set via a config option

config.yaml

@@ -56,6 +56,12 @@ options:
     default: "yes"
     type: string
     description: Whether to run nova-api and nova-network on the compute nodes.
+  disk-cachemodes:
+    default:
+    type: string
+    description: |
+      Specific cachemodes to use for different disk types e.g:
+      file=directsync,block=none
   enable-resize:
     default: False
     type: boolean

hooks/nova_compute_context.py

@@ -103,6 +103,9 @@ class NovaComputeLibvirtContext(context.OSContextGenerator):
         if config('instances-path') is not None:
             ctxt['instances_path'] = config('instances-path')
 
+        if config('disk-cachemodes'):
+            ctxt['disk_cachemodes'] = config('disk-cachemodes')
+
         return ctxt
 
 

templates/havana/nova.conf

@@ -114,3 +114,8 @@ keymap = {{ console_keymap }}
 server_listen = 0.0.0.0
 server_proxyclient_address = {{ console_listen_addr }}
 {% endif -%}
+
+{% if disk_cachemodes -%}
+[libvirt]
+disk_cachemodes = {{ disk_cachemodes }}
+{% endif -%}

templates/juno/nova.conf

@@ -114,4 +114,6 @@ rbd_secret_uuid = {{ rbd_secret_uuid }}
 {% if live_migration_uri -%}
 live_migration_uri = {{ live_migration_uri }}
 {% endif -%}
-
+{% if disk_cachemodes -%}
+disk_cachemodes = {{ disk_cachemodes }}
+{% endif -%}

unit_tests/test_nova_compute_contexts.py

@@ -181,6 +181,13 @@ class NovaComputeContextTests(CharmTestCase):
         self.assertEquals(
             {'libvirtd_opts': '-d -l', 'listen_tls': 0}, libvirt())
 
+    def test_libvirt_disk_cachemodes(self):
+        self.test_config.set('disk-cachemodes', 'file=unsafe,block=none')
+        libvirt = context.NovaComputeLibvirtContext()
+        self.assertEquals(
+            {'libvirtd_opts': '-d', 'listen_tls': 0,
+             'disk_cachemodes': 'file=unsafe,block=none'}, libvirt())
+
     @patch.object(context.NeutronComputeContext, 'network_manager')
     @patch.object(context.NeutronComputeContext, 'plugin')
     def test_disable_security_groups_true(self, plugin, nm):