Add a volume driver in Nova for Scality SOFS

Scality SOFS is a network filesystem mounted with FUSE, with most
options given in a configuration file. Given a mount point and a SOFS
configuration file as driver options, the Scality volume driver mounts
SOFS, and then creates, accesses and deletes volumes as regular
(sparse) files on SOFS.

Change-Id: I84bf268e5a2c5c33b8706830e8067914fae44aed
Implements: blueprint scality-volume-driver

etc/nova/rootwrap.d/compute.filters

@@ -14,6 +14,7 @@ tune2fs: CommandFilter, /sbin/tune2fs, root
 # nova/virt/disk/api.py: 'mount', '-o', 'bind', src, target
 # nova/virt/xenapi/vm_utils.py: 'mount', '-t', 'ext2,ext3,ext4,reiserfs'..
 # nova/virt/configdrive.py: 'mount', device, mountdir
+# nova/virt/libvirt/volume.py: 'mount', '-t', 'sofs' ...
 mount: CommandFilter, /bin/mount, root
 
 # nova/virt/disk/mount/api.py: 'umount', mapped_device

nova/tests/test_libvirt_volume.py

@@ -15,6 +15,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import fixtures
 import os
 
 from oslo.config import cfg
@@ -547,3 +548,43 @@ class LibvirtVolumeTestCase(test.TestCase):
                               "/0000:05:00.3/0000:06:00.6/host2/fc_host/host2"}
         pci_num = libvirt_driver._get_pci_num(hba)
         self.assertEqual("0000:06:00.6", pci_num)
+
+    def test_libvirt_scality_driver(self):
+        tempdir = self.useFixture(fixtures.TempDir()).path
+        TEST_MOUNT = os.path.join(tempdir, 'fake_mount')
+        TEST_CONFIG = os.path.join(tempdir, 'fake_config')
+        TEST_VOLDIR = 'volumes'
+        TEST_VOLNAME = 'volume_name'
+        TEST_CONN_INFO = {
+            'data': {
+                'sofs_path': os.path.join(TEST_VOLDIR, TEST_VOLNAME)
+            }
+        }
+        TEST_VOLPATH = os.path.join(TEST_MOUNT,
+                                    TEST_VOLDIR,
+                                    TEST_VOLNAME)
+        TEST_DISK_INFO = {
+            "bus": "virtio",
+            "dev": "vde",
+            "type": "disk",
+        }
+
+        open(TEST_CONFIG, "w+").close()
+        os.makedirs(os.path.join(TEST_MOUNT, 'sys'))
+
+        def _access_wrapper(path, flags):
+            if path == '/sbin/mount.sofs':
+                return True
+            else:
+                return os.access(path, flags)
+
+        self.stubs.Set(os, 'access', _access_wrapper)
+
+        self.flags(scality_sofs_config=TEST_CONFIG,
+                   scality_sofs_mount_point=TEST_MOUNT)
+        driver = volume.LibvirtScalityVolumeDriver(self.fake_conn)
+        conf = driver.connect_volume(TEST_CONN_INFO, TEST_DISK_INFO)
+
+        tree = conf.format_dom()
+        self.assertEqual(tree.get('type'), 'file')
+        self.assertEqual(tree.find('./source').get('file'), TEST_VOLPATH)

nova/virt/libvirt/driver.py

@@ -166,7 +166,9 @@ libvirt_opts = [
                   'glusterfs='
                       'nova.virt.libvirt.volume.LibvirtGlusterfsVolumeDriver',
                   'fibre_channel=nova.virt.libvirt.volume.'
-                      'LibvirtFibreChannelVolumeDriver'
+                      'LibvirtFibreChannelVolumeDriver',
+                  'scality='
+                      'nova.virt.libvirt.volume.LibvirtScalityVolumeDriver',
                   ],
                 help='Libvirt handlers for remote volumes.'),
     cfg.StrOpt('libvirt_disk_prefix',

nova/virt/libvirt/volume.py

@@ -21,6 +21,8 @@
 import hashlib
 import os
 import time
+import urllib2
+import urlparse
 
 from oslo.config import cfg
 
@@ -63,6 +65,12 @@ volume_opts = [
     cfg.BoolOpt('libvirt_iscsi_use_multipath',
                 default=False,
                 help='use multipath connection of the iSCSI volume'),
+    cfg.StrOpt('scality_sofs_config',
+               default=None,
+               help='Path or URL to Scality SOFS configuration file'),
+    cfg.StrOpt('scality_sofs_mount_point',
+               default='$state_path/scality',
+               help='Base dir where Scality SOFS shall be mounted'),
     ]
 
 CONF = cfg.CONF
@@ -749,3 +757,74 @@ class LibvirtFibreChannelVolumeDriver(LibvirtBaseVolumeDriver):
         # all of them
         for device in devices:
             linuxscsi.remove_device(device)
+
+
+class LibvirtScalityVolumeDriver(LibvirtBaseVolumeDriver):
+    """Scality SOFS Nova driver. Provide hypervisors with access
+    to sparse files on SOFS. """
+
+    def __init__(self, connection):
+        """Create back-end to SOFS and check connection."""
+        super(LibvirtScalityVolumeDriver,
+              self).__init__(connection, is_block_dev=False)
+
+    def connect_volume(self, connection_info, disk_info):
+        """Connect the volume. Returns xml for libvirt."""
+        self._check_prerequisites()
+        self._mount_sofs()
+        conf = super(LibvirtScalityVolumeDriver,
+                     self).connect_volume(connection_info, disk_info)
+        path = os.path.join(CONF.scality_sofs_mount_point,
+                            connection_info['data']['sofs_path'])
+        conf.source_type = 'file'
+        conf.source_path = path
+
+        # The default driver cache policy is 'none', and this causes
+        # qemu/kvm to open the volume file with O_DIRECT, which is
+        # rejected by FUSE (on kernels older than 3.3). Scality SOFS
+        # is FUSE based, so we must provide a more sensible default.
+        conf.driver_cache = 'writethrough'
+
+        return conf
+
+    def _check_prerequisites(self):
+        """Sanity checks before attempting to mount SOFS."""
+
+        # config is mandatory
+        config = CONF.scality_sofs_config
+        if not config:
+            msg = _("Value required for 'scality_sofs_config'")
+            LOG.warn(msg)
+            raise exception.NovaException(msg)
+
+        # config can be a file path or a URL, check it
+        if urlparse.urlparse(config).scheme == '':
+            # turn local path into URL
+            config = 'file://%s' % config
+        try:
+            urllib2.urlopen(config, timeout=5).close()
+        except urllib2.URLError as e:
+            msg = _("Cannot access 'scality_sofs_config': %s") % e
+            LOG.warn(msg)
+            raise exception.NovaException(msg)
+
+        # mount.sofs must be installed
+        if not os.access('/sbin/mount.sofs', os.X_OK):
+            msg = _("Cannot execute /sbin/mount.sofs")
+            LOG.warn(msg)
+            raise exception.NovaException(msg)
+
+    def _mount_sofs(self):
+        config = CONF.scality_sofs_config
+        mount_path = CONF.scality_sofs_mount_point
+        sysdir = os.path.join(mount_path, 'sys')
+
+        if not os.path.isdir(mount_path):
+            utils.execute('mkdir', '-p', mount_path)
+        if not os.path.isdir(sysdir):
+            utils.execute('mount', '-t', 'sofs', config, mount_path,
+                          run_as_root=True)
+        if not os.path.isdir(sysdir):
+            msg = _("Cannot mount Scality SOFS, check syslog for errors")
+            LOG.warn(msg)
+            raise exception.NovaException(msg)