Capture timeout exception when deleting NamespaceFixture

Until the related bug is fixed, if the namespace created in a
NamespaceFixture cannot be deleted due to a timeout exception,
the exception will be dismissed and a warning message logged.

The leftover namespace will not affect other test cases.

Change-Id: Idb262024ca74aaa924525150e610642f493c5dc4
Related-Bug: #1838793

neutron/tests/common/helpers.py

@@ -15,8 +15,10 @@
 import datetime
 from distutils import version
 import functools
+import math
 import os
 import random
+import signal
 
 from neutron_lib.agent import topics
 from neutron_lib import constants
@@ -229,3 +231,47 @@ def skip_if_ovs_older_than(ovs_version):
             return f(test)
         return check_ovs_and_skip
     return skip_if_bad_ovs
+
+
+class TestTimerTimeout(Exception):
+    pass
+
+
+class TestTimer(object):
+    """Timer context manager class for testing.
+
+    This class can be used inside a fixtures._fixtures.timeout.Timeout context.
+    This class will halt the timeout counter and divert temporary the fixtures
+    timeout exception. The goal of this class is to use the SIGALRM event
+    without affecting the test case timeout counter.
+    """
+    def __init__(self, timeout):
+        self._timeout = int(timeout)
+        self._old_handler = None
+        self._old_timer = None
+        self._alarm_fn = getattr(signal, 'alarm', None)
+
+    def _timeout_handler(self, *args, **kwargs):
+        raise TestTimerTimeout()
+
+    def __enter__(self):
+        self._old_handler = signal.signal(signal.SIGALRM,
+                                          self._timeout_handler)
+        self._old_timer = math.ceil(signal.getitimer(signal.ITIMER_REAL)[0])
+        if self._alarm_fn:
+            self._alarm_fn(self._timeout)
+        return self
+
+    def __exit__(self, exc, value, traceback):
+        if self._old_handler:
+            signal.signal(signal.SIGALRM, self._old_handler)
+
+        if self._old_timer == 0:
+            return
+
+        # If timer has expired, set the minimum required value (1) to activate
+        # the SIGALRM event.
+        timeout = self._old_timer - self._timeout
+        timeout = 1 if timeout <= 0 else timeout
+        if self._alarm_fn:
+            self._alarm_fn(timeout)

neutron/tests/common/net_helpers.py

@@ -45,6 +45,7 @@ from neutron.db import db_base_plugin_common as db_base
 from neutron.plugins.ml2.drivers.linuxbridge.agent import \
     linuxbridge_neutron_agent as linuxbridge_agent
 from neutron.tests.common import base as common_base
+from neutron.tests.common import helpers
 from neutron.tests import tools
 
 LOG = logging.getLogger(__name__)
@@ -612,10 +613,18 @@ class NamespaceFixture(fixtures.Fixture):
         self.addCleanup(self.destroy)
 
     def destroy(self):
-        if self.ip_wrapper.netns.exists(self.name):
-            for pid in ip_lib.list_namespace_pids(self.name):
-                utils.kill_process(pid, signal.SIGKILL, run_as_root=True)
-            self.ip_wrapper.netns.delete(self.name)
+        # TODO(ralonsoh): once the issue in LP#1838793 is properly fixed, we
+        # can remove this workaround (TestTimer context).
+        with helpers.TestTimer(5):
+            try:
+                if self.ip_wrapper.netns.exists(self.name):
+                    for pid in ip_lib.list_namespace_pids(self.name):
+                        utils.kill_process(pid, signal.SIGKILL,
+                                           run_as_root=True)
+                    self.ip_wrapper.netns.delete(self.name)
+            except helpers.TestTimerTimeout:
+                LOG.warning('Namespace %s was not deleted due to a timeout.',
+                            self.name)
 
 
 class VethFixture(fixtures.Fixture):