Introduced flag base_dir_name. Fixes bug 973194

rebased from master.

If user faces locking related problem when two nova-compute hosts
sharing same disk area via nfs, try to download same image into
cache concurrently - Then base_dir_name can be set to "_base_$my_ip" in
nova.conf

Default value for base_dir_name is "_base" thus retaining existing
behavior.

Change-Id: Icff10ed75ba83f7256731614dc9e01e578b347a4

6 files changed, 22 insertions, 9 deletions

diff --git a/Authors b/Authors
index a229313bad..b9ad28b7f4 100644
--- a/Authors
+++ b/Authors
@@ -122,6 +122,7 @@ Likitha Shetty <likitha.shetty@citrix.com>
 Loganathan Parthipan <parthipan@hp.com>
 Lorin Hochstein <lorin@nimbisservices.com>
 Lvov Maxim <usrleon@gmail.com>
+Mandar Vaze <mandar.vaze@vertex.co.in>
 Mandell Degerness <mdegerne@gmail.com>
 Mark McClain <mark.mcclain@dreamhost.com>
 Mark McLoughlin <markmc@redhat.com>
diff --git a/nova/compute/manager.py b/nova/compute/manager.py
index 48e135b255..053e80ec59 100644
--- a/nova/compute/manager.py
+++ b/nova/compute/manager.py
@@ -28,6 +28,7 @@ terminating it.
 **Related Flags**
 
 :instances_path:  Where instances are kept on disk
+:base_dir_name:  Where cached images are stored under instances_path
 :compute_driver:  Name of class that is used to handle virtualization, loaded
                   by :func:`nova.utils.import_object`
 
@@ -72,6 +73,11 @@ compute_opts = [
     cfg.StrOpt('instances_path',
                default='$state_path/instances',
                help='where instances are stored on disk'),
+    cfg.StrOpt('base_dir_name',
+               default='_base',
+               help="where cached images are stored under $instances_path"
+                    "This is NOT full path - just a folder name"
+                    "For per-compute-host cached images, Set to _base_$my_ip"),
     cfg.StrOpt('compute_driver',
                default='nova.virt.connection.get_connection',
                help='Driver to use for controlling virtualization'),
diff --git a/nova/tests/test_imagecache.py b/nova/tests/test_imagecache.py
index 9cf400320c..f1d5aa5723 100644
--- a/nova/tests/test_imagecache.py
+++ b/nova/tests/test_imagecache.py
@@ -36,6 +36,7 @@ from nova.virt.libvirt import utils as virtutils
 
 
 flags.DECLARE('instances_path', 'nova.compute.manager')
+flags.DECLARE('base_dir_name', 'nova.compute.manager')
 FLAGS = flags.FLAGS
 
 LOG = log.getLogger(__name__)
@@ -155,7 +156,7 @@ class ImageCacheManagerTestCase(test.TestCase):
         self.stubs.Set(virtutils, 'get_disk_backing_file',
                        lambda x: 'e97222e91fc4241f49a7f520d1dcf446751129b3_sm')
 
-        found = os.path.join(FLAGS.instances_path, '_base',
+        found = os.path.join(FLAGS.instances_path, FLAGS.base_dir_name,
                              'e97222e91fc4241f49a7f520d1dcf446751129b3_sm')
 
         image_cache_manager = imagecache.ImageCacheManager()
@@ -177,7 +178,7 @@ class ImageCacheManagerTestCase(test.TestCase):
                        lambda x: ('e97222e91fc4241f49a7f520d1dcf446751129b3_'
                                   '10737418240'))
 
-        found = os.path.join(FLAGS.instances_path, '_base',
+        found = os.path.join(FLAGS.instances_path, FLAGS.base_dir_name,
                              'e97222e91fc4241f49a7f520d1dcf446751129b3_'
                              '10737418240')
 
@@ -198,7 +199,7 @@ class ImageCacheManagerTestCase(test.TestCase):
         self.stubs.Set(virtutils, 'get_disk_backing_file',
                        lambda x: 'e97222e91fc4241f49a7f520d1dcf446751129b3_sm')
 
-        found = os.path.join(FLAGS.instances_path, '_base',
+        found = os.path.join(FLAGS.instances_path, FLAGS.base_dir_name,
                              'e97222e91fc4241f49a7f520d1dcf446751129b3_sm')
 
         image_cache_manager = imagecache.ImageCacheManager()
@@ -521,6 +522,7 @@ class ImageCacheManagerTestCase(test.TestCase):
         hashed_42 = '92cfceb39d57d914ed8b14d0e37643de0797ae56'
 
         self.flags(instances_path='/instance_path')
+        self.flags(base_dir_name='_base')
         self.flags(remove_unused_base_images=True)
 
         base_file_list = ['00000001',
diff --git a/nova/tests/test_libvirt.py b/nova/tests/test_libvirt.py
index cdc9121d7a..f12cad47d1 100644
--- a/nova/tests/test_libvirt.py
+++ b/nova/tests/test_libvirt.py
@@ -322,7 +322,7 @@ class CacheConcurrencyTestCase(test.TestCase):
         self.flags(instances_path='nova.compute.manager')
 
         def fake_exists(fname):
-            basedir = os.path.join(FLAGS.instances_path, '_base')
+            basedir = os.path.join(FLAGS.instances_path, FLAGS.base_dir_name)
             if fname == basedir:
                 return True
             return False
@@ -1317,9 +1317,10 @@ class LibvirtConnTestCase(test.TestCase):
         if os.path.isdir(path):
             shutil.rmtree(path)
 
-        path = os.path.join(FLAGS.instances_path, '_base')
+        path = os.path.join(FLAGS.instances_path, FLAGS.base_dir_name)
         if os.path.isdir(path):
-            shutil.rmtree(os.path.join(FLAGS.instances_path, '_base'))
+            shutil.rmtree(os.path.join(FLAGS.instances_path,
+                                       FLAGS.base_dir_name))
 
     def test_get_host_ip_addr(self):
         conn = connection.LibvirtConnection(False)
diff --git a/nova/virt/libvirt/connection.py b/nova/virt/libvirt/connection.py
index 5facc1091f..f1e56803a7 100644
--- a/nova/virt/libvirt/connection.py
+++ b/nova/virt/libvirt/connection.py
@@ -1090,7 +1090,8 @@ class LibvirtConnection(driver.ComputeDriver):
 
         generating = 'image_id' not in kwargs
         if not os.path.exists(target):
-            base_dir = os.path.join(FLAGS.instances_path, '_base')
+            base_dir = os.path.join(FLAGS.instances_path, FLAGS.base_dir_name)
+
             if not os.path.exists(base_dir):
                 libvirt_utils.ensure_tree(base_dir)
             base = os.path.join(base_dir, fname)
diff --git a/nova/virt/libvirt/imagecache.py b/nova/virt/libvirt/imagecache.py
index f92376a174..adf8214005 100644
--- a/nova/virt/libvirt/imagecache.py
+++ b/nova/virt/libvirt/imagecache.py
@@ -58,6 +58,7 @@ imagecache_opts = [
     ]
 
 flags.DECLARE('instances_path', 'nova.compute.manager')
+flags.DECLARE('base_dir_name', 'nova.compute.manager')
 FLAGS = flags.FLAGS
 FLAGS.register_opts(imagecache_opts)
 
@@ -178,7 +179,8 @@ class ImageCacheManager(object):
                                'backing': backing_file})
 
                     backing_path = os.path.join(FLAGS.instances_path,
-                                                '_base', backing_file)
+                                                FLAGS.base_dir_name,
+                                                backing_file)
                     if not backing_path in inuse_images:
                         inuse_images.append(backing_path)
 
@@ -372,7 +374,7 @@ class ImageCacheManager(object):
         # created, but may remain from previous versions.
         self._reset_state()
 
-        base_dir = os.path.join(FLAGS.instances_path, '_base')
+        base_dir = os.path.join(FLAGS.instances_path, FLAGS.base_dir_name)
         if not os.path.exists(base_dir):
             LOG.debug(_('Skipping verification, no base directory at %s'),
                       base_dir)