Check a namespace existence by checking only its own directory

To check the existance of a namespace, instead of listing the
namespaces directory (by default "/var/run/netns"), this patch
directly checks the existence of the namespace directory, using
"os.path.exists".

This check is faster than listing the whole directory and avoids
timeout problems as reported in the related bug.

Conflicts:
      neutron/privileged/agent/linux/utils.py

Closes-Bug: #1947974
Change-Id: I558d50d28378beb3710d98a2113ff9549c82ae17
(cherry picked from commit 8127221479)

neutron/agent/linux/ip_lib.py

@@ -14,6 +14,7 @@
 #    under the License.
 
 import errno
+from os import path
 import re
 import threading
 import time
@@ -35,6 +36,7 @@ from neutron._i18n import _
 from neutron.agent.common import utils
 from neutron.common import utils as common_utils
 from neutron.privileged.agent.linux import ip_lib as privileged
+from neutron.privileged.agent.linux import utils as priv_utils
 
 LOG = logging.getLogger(__name__)
 
@@ -931,9 +933,16 @@ def network_namespace_exists(namespace, try_is_ready=False, **kwargs):
                          is ready to be operated.
     :param kwargs: Callers add any filters they use as kwargs
     """
+    if not namespace:
+        return False
+
     if not try_is_ready:
-        output = list_network_namespaces(**kwargs)
-        return namespace in output
+        nspath = kwargs.get('nspath') or netns.NETNS_RUN_DIR
+        nspath += '/' + namespace
+        if cfg.CONF.AGENT.use_helper_for_ns_read:
+            return priv_utils.path_exists(nspath)
+        else:
+            return path.exists(nspath)
 
     try:
         privileged.open_namespace(namespace)

neutron/privileged/agent/linux/utils.py

@@ -13,6 +13,7 @@
 #    under the License.
 
 import os
+from os import path
 import re
 
 from oslo_concurrency import processutils
@@ -45,5 +46,10 @@ def _find_listen_pids_namespace(namespace):
 
 
 @privileged.default.entrypoint
-def delete_if_exists(path, remove=os.unlink):
-    fileutils.delete_if_exists(path, remove=remove)
+def delete_if_exists(_path, remove=os.unlink):
+    fileutils.delete_if_exists(_path, remove=remove)
+
+
+@privileged.default.entrypoint
+def path_exists(_path):
+    return path.exists(_path)

neutron/tests/common/net_helpers.py

@@ -637,8 +637,8 @@ class VethFixture(fixtures.Fixture):
     def destroy(self):
         for port in self.ports:
             ip_wrapper = ip_lib.IPWrapper(port.namespace)
-            if (ip_wrapper.netns.exists(port.namespace) or
-                    port.namespace is None):
+            if (port.namespace is None or
+                    ip_wrapper.netns.exists(port.namespace)):
                 try:
                     ip_wrapper.del_veth(port.name)
                     break

neutron/tests/functional/agent/linux/test_ip_lib.py

@@ -660,10 +660,16 @@ class NamespaceTestCase(functional_base.BaseSudoTestCase):
         ip_lib.delete_network_namespace(self.namespace)
 
     def test_network_namespace_exists_ns_exists(self):
-        self.assertTrue(ip_lib.network_namespace_exists(self.namespace))
+        for use_helper_for_ns_read in (True, False):
+            cfg.CONF.set_override('use_helper_for_ns_read',
+                                  use_helper_for_ns_read, 'AGENT')
+            self.assertTrue(ip_lib.network_namespace_exists(self.namespace))
 
     def test_network_namespace_exists_ns_doesnt_exists(self):
-        self.assertFalse(ip_lib.network_namespace_exists('another_ns'))
+        for use_helper_for_ns_read in (True, False):
+            cfg.CONF.set_override('use_helper_for_ns_read',
+                                  use_helper_for_ns_read, 'AGENT')
+            self.assertFalse(ip_lib.network_namespace_exists('another_ns'))
 
     def test_network_namespace_exists_ns_exists_try_is_ready(self):
         self.assertTrue(ip_lib.network_namespace_exists(self.namespace,

neutron/tests/unit/agent/l3/test_agent.py

@@ -61,6 +61,7 @@ from neutron.conf.agent import common as agent_config
 from neutron.conf.agent.l3 import config as l3_config
 from neutron.conf.agent.l3 import ha as ha_conf
 from neutron.conf import common as base_config
+from neutron.privileged.agent.linux import utils as priv_utils
 from neutron.tests import base
 from neutron.tests.common import l3_test_common
 from neutron.tests.unit.agent.linux.test_utils import FakeUser
@@ -101,6 +102,8 @@ class BasicRouterOperationsFramework(base.BaseTestCase):
         self.list_network_namespaces_p = mock.patch(
             'neutron.agent.linux.ip_lib.list_network_namespaces')
         self.list_network_namespaces = self.list_network_namespaces_p.start()
+        self.path_exists_p = mock.patch.object(priv_utils, 'path_exists')
+        self.path_exists = self.path_exists_p.start()
 
         self.ensure_dir = mock.patch(
             'oslo_utils.fileutils.ensure_tree').start()

neutron/tests/unit/agent/linux/test_ip_lib.py

@@ -864,31 +864,6 @@ class TestIpNetnsCommand(TestIPCmdBase):
         self.netns_cmd.delete('ns')
         remove.assert_called_once_with('ns')
 
-    @mock.patch.object(pyroute2.netns, 'listnetns')
-    @mock.patch.object(priv_lib, 'list_netns')
-    def test_namespace_exists_use_helper(self, priv_listnetns, listnetns):
-        self.config(group='AGENT', use_helper_for_ns_read=True)
-        priv_listnetns.return_value = NETNS_SAMPLE
-        # need another instance to avoid mocking
-        netns_cmd = ip_lib.IpNetnsCommand(ip_lib.SubProcessBase())
-        self.assertTrue(
-            netns_cmd.exists('bbbbbbbb-bbbb-bbbb-bbbb-bbbbbbbbbbbb'))
-        self.assertEqual(1, priv_listnetns.call_count)
-        self.assertFalse(listnetns.called)
-
-    @mock.patch.object(pyroute2.netns, 'listnetns')
-    @mock.patch.object(priv_lib, 'list_netns')
-    def test_namespace_does_not_exist_no_helper(self, priv_listnetns,
-                                                listnetns):
-        self.config(group='AGENT', use_helper_for_ns_read=False)
-        listnetns.return_value = NETNS_SAMPLE
-        # need another instance to avoid mocking
-        netns_cmd = ip_lib.IpNetnsCommand(ip_lib.SubProcessBase())
-        self.assertFalse(
-            netns_cmd.exists('bbbbbbbb-1111-2222-3333-bbbbbbbbbbbb'))
-        self.assertEqual(1, listnetns.call_count)
-        self.assertFalse(priv_listnetns.called)
-
     def test_execute(self):
         self.parent.namespace = 'ns'
         with mock.patch('neutron.agent.common.utils.execute') as execute: