Provide a configdrive helper which uses contextlib.

As suggested on review of Ib23d117ad4cd5dc92298a0812eb468f7d557417c.

Resolves bug 1092248.

Change-Id: I2829ac60732b86b9853983b03ef6f30f5c5a3283

3 files changed, 27 insertions, 20 deletions

diff --git a/nova/virt/configdrive.py b/nova/virt/configdrive.py
index 2a1001577..321bf8389 100644
--- a/nova/virt/configdrive.py
+++ b/nova/virt/configdrive.py
@@ -17,6 +17,7 @@
 
 """Config Drive v2 helper."""
 
+import contextlib
 import os
 import shutil
 import tempfile
@@ -54,7 +55,18 @@ CONF = cfg.CONF
 CONF.register_opts(configdrive_opts)
 
 
-class ConfigDriveBuilder(object):
+@contextlib.contextmanager
+def config_drive_helper(instance_md=None):
+    cdb = _ConfigDriveBuilder(instance_md=instance_md)
+    try:
+        yield cdb
+    finally:
+        cdb.cleanup()
+
+
+class _ConfigDriveBuilder(object):
+    """Don't use this directly, use the fancy pants contextlib helper above!"""
+
     def __init__(self, instance_md=None):
         self.imagefile = None
 
diff --git a/nova/virt/hyperv/vmops.py b/nova/virt/hyperv/vmops.py
index fea1034f4..4ff89ef5e 100644
--- a/nova/virt/hyperv/vmops.py
+++ b/nova/virt/hyperv/vmops.py
@@ -194,15 +194,13 @@ class VMOps(baseops.BaseOps):
         LOG.info(_('Creating config drive at %(path)s'),
                  {'path': configdrive_path_iso}, instance=instance)
 
-        cdb = configdrive.ConfigDriveBuilder(instance_md=inst_md)
-        try:
-            cdb.make_drive(configdrive_path_iso)
-        except exception.ProcessExecutionError, e:
-            LOG.error(_('Creating config drive failed with error: %s'),
-                      e, instance=instance)
-            raise
-        finally:
-            cdb.cleanup()
+        with configdrive.config_drive_helper(instance_md=inst_md) as cdb:
+            try:
+                cdb.make_drive(configdrive_path_iso)
+            except exception.ProcessExecutionError, e:
+                LOG.error(_('Creating config drive failed with error: %s'),
+                          e, instance=instance)
+                raise
 
         if not CONF.config_drive_cdrom:
             drive_type = constants.IDE_DISK
diff --git a/nova/virt/libvirt/driver.py b/nova/virt/libvirt/driver.py
index 9c78dc57d..198a8100a 100644
--- a/nova/virt/libvirt/driver.py
+++ b/nova/virt/libvirt/driver.py
@@ -1446,20 +1446,17 @@ class LibvirtDriver(driver.ComputeDriver):
 
             inst_md = instance_metadata.InstanceMetadata(instance,
                 content=files, extra_md=extra_md)
-            cdb = configdrive.ConfigDriveBuilder(instance_md=inst_md)
-            try:
+            with configdrive.config_drive_helper(instance_md=inst_md) as cdb:
                 configdrive_path = basepath(fname='disk.config')
                 LOG.info(_('Creating config drive at %(path)s'),
                          {'path': configdrive_path}, instance=instance)
 
-                cdb.make_drive(configdrive_path)
-            except exception.ProcessExecutionError, e:
-                LOG.error(_('Creating config drive failed with error: %s'),
-                          e, instance=instance)
-                raise
-
-            finally:
-                cdb.cleanup()
+                try:
+                    cdb.make_drive(configdrive_path)
+                except exception.ProcessExecutionError, e:
+                    LOG.error(_('Creating config drive failed with error: %s'),
+                              e, instance=instance)
+                    raise
 
         elif any((key, net, metadata, admin_pass, files)):
             # If we're not using config_drive, inject into root fs