Fixed concurrent access to direct io test file

When instances are deployed concurrently on multiple
compute nodes, nova-compute may fail on checking
direct io capabilities when instance_path is shared
across nodes. This fails on shared storage, that
doesn't support concurrent write access to the
same file, i.e. Virtuozzo Storage. To fix that we add
random string at the end of test file name.

Closes-Bug: #1727369
Change-Id: I085ade355fba0e9727a38d2dcbc9cffa735a62d1
Signed-off-by: Pavel Glushchak <pglushchak@virtuozzo.com>

nova/privsep/utils.py

@@ -27,6 +27,7 @@ import os
 from oslo_log import log as logging
 from oslo_utils import excutils
 
+from nova import utils as nova_utils
 
 LOG = logging.getLogger(__name__)
 
@@ -37,7 +38,9 @@ def supports_direct_io(dirpath):
         LOG.debug("This python runtime does not support direct I/O")
         return False
 
-    testfile = os.path.join(dirpath, ".directio.test")
+    file_name = "%s.%s" % (".directio.test",
+                           nova_utils.generate_random_string())
+    testfile = os.path.join(dirpath, file_name)
 
     hasDirectIO = True
     fd = None

nova/tests/functional/test_servers.py

@@ -633,6 +633,8 @@ class ServersTest(ServersTestBase):
         self.assertIn('reservation_id', response)
         reservation_id = response['reservation_id']
         self.assertNotIn(reservation_id, ['', None])
+        # Assert that the reservation_id itself has the expected format
+        self.assertRegex(reservation_id, 'r-[0-9a-zA-Z]{8}')
 
         # Create 1 more server, which should not return a reservation_id
         server = self._build_minimal_create_server_request()

nova/tests/unit/privsep/test_utils.py

@@ -36,21 +36,25 @@ class SupportDirectIOTestCase(test.NoDBTestCase):
         self.einval.errno = errno.EINVAL
         self.enoent = OSError()
         self.enoent.errno = errno.ENOENT
-        self.test_path = os.path.join('.', '.directio.test')
+        self.test_path = os.path.join('.', '.directio.test.abc123')
         self.io_flags = os.O_CREAT | os.O_WRONLY | os.O_DIRECT
 
         open_patcher = mock.patch('os.open')
         write_patcher = mock.patch('os.write')
         close_patcher = mock.patch('os.close')
         unlink_patcher = mock.patch('os.unlink')
+        random_string_patcher = mock.patch('nova.utils.generate_random_string',
+                                           return_value='abc123')
         self.addCleanup(open_patcher.stop)
         self.addCleanup(write_patcher.stop)
         self.addCleanup(close_patcher.stop)
         self.addCleanup(unlink_patcher.stop)
+        self.addCleanup(random_string_patcher.stop)
         self.mock_open = open_patcher.start()
         self.mock_write = write_patcher.start()
         self.mock_close = close_patcher.start()
         self.mock_unlink = unlink_patcher.start()
+        random_string_patcher.start()
 
     def test_supports_direct_io(self):
         self.mock_open.return_value = 3

nova/tests/unit/virt/libvirt/test_driver.py

@@ -2435,6 +2435,8 @@ class LibvirtConnTestCase(test.NoDBTestCase,
             self.assertEqual(0, len(cfg.cputune.vcpupin))
             self.assertIsNone(cfg.cpu.numa)
 
+    @mock.patch('nova.privsep.utils.supports_direct_io',
+                new=mock.Mock(return_value=True))
     @mock.patch.object(
         host.Host, "is_cpu_control_policy_capable", return_value=True)
     def test_get_guest_config_numa_host_instance_no_fit(self, is_able):
@@ -2686,6 +2688,8 @@ class LibvirtConnTestCase(test.NoDBTestCase,
             self.assertEqual(0, len(cfg.cputune.vcpupin))
             self.assertIsNone(cfg.cpu.numa)
 
+    @mock.patch('nova.privsep.utils.supports_direct_io',
+                new=mock.Mock(return_value=True))
     @mock.patch.object(
         host.Host, "is_cpu_control_policy_capable", return_value=True)
     def test_get_guest_config_numa_host_instance_2pci_no_fit(self, is_able):

nova/utils.py

@@ -244,9 +244,13 @@ def ssh_execute(dest, *cmd, **kwargs):
 
 
 def generate_uid(topic, size=8):
+    random_string = generate_random_string(size)
+    return '%s-%s' % (topic, random_string)
+
+
+def generate_random_string(size=8):
     characters = '01234567890abcdefghijklmnopqrstuvwxyz'
-    choices = [random.choice(characters) for _x in range(size)]
-    return '%s-%s' % (topic, ''.join(choices))
+    return ''.join([random.choice(characters) for _x in range(size)])
 
 
 # Default symbols to use for passwords. Avoids visually confusing characters.