Limit usage of resources in the fullstack tests job

To limit usage of resources (mostly memory) in the fullstack job and
to avoid oom killer to kill e.g. mysqld service, this patch:

* Makes number of API workers changeable by tests, as a parameter to
  EnvironmentDescription and defaults its value to 1. As neutron server
  is spawned separately for each test and is used only to process just
  few API requests during that single test so this should be still
  enough there, and where more API workers are needed (like some dhcp HA
  tests: TestDhcpAgentHARaceCondition) it can be changed,
* reduces number of test run workers from 4 to 3 - job will run slower
  but hopefully more stable,
* in the functional and fullstack tests job definition disable etcd3
  service - this will not save us a lot of memory but still it's not
  needed at all so why to run it there.

Change-Id: If19803ab6db144e2d17d6805d379c1c76d8fa343
Closes-Bug: #1906366

neutron/tests/fullstack/resources/config.py

@@ -82,7 +82,7 @@ class NeutronConfigFixture(ConfigFixture):
                      'password': rabbitmq_environment.password,
                      'host': rabbitmq_environment.host,
                      'vhost': rabbitmq_environment.vhost},
-                'api_workers': '2',
+                'api_workers': str(env_desc.api_workers),
             },
             'database': {
                 'connection': connection,

neutron/tests/fullstack/resources/environment.py

@@ -40,7 +40,8 @@ class EnvironmentDescription(object):
                  global_mtu=constants.DEFAULT_NETWORK_MTU,
                  debug_iptables=False, log=False, report_bandwidths=False,
                  has_placement=False, placement_port=None,
-                 dhcp_scheduler_class=None, ml2_extension_drivers=None):
+                 dhcp_scheduler_class=None, ml2_extension_drivers=None,
+                 api_workers=1):
         self.network_type = network_type
         self.l2_pop = l2_pop
         self.qos = qos
@@ -62,6 +63,7 @@ class EnvironmentDescription(object):
         if self.log:
             self.service_plugins += ',log'
         self.ml2_extension_drivers = ml2_extension_drivers
+        self.api_workers = api_workers
 
     @property
     def tunneling_enabled(self):

neutron/tests/fullstack/test_dhcp_agent.py

@@ -38,6 +38,7 @@ class BaseDhcpAgentTest(base.BaseFullStackTestCase):
     ]
     boot_vm_for_test = True
     dhcp_scheduler_class = None
+    api_workers = 1
 
     def setUp(self):
         host_descriptions = [
@@ -52,6 +53,7 @@ class BaseDhcpAgentTest(base.BaseFullStackTestCase):
                 arp_responder=False,
                 agent_down_time=self.agent_down_time,
                 dhcp_scheduler_class=self.dhcp_scheduler_class,
+                api_workers=self.api_workers,
             ),
             host_descriptions)
 
@@ -205,6 +207,7 @@ class TestDhcpAgentHARaceCondition(BaseDhcpAgentTest):
     agent_down_time = 30
     number_of_hosts = 2
     boot_vm_for_test = False
+    api_workers = 2
     dhcp_scheduler_class = ('neutron.tests.fullstack.schedulers.dhcp.'
                             'AlwaysTheOtherAgentScheduler')
 

tox.ini

@@ -76,7 +76,7 @@ deps =
 commands =
   {toxinidir}/tools/generate_dhclient_script_for_fullstack.sh {envdir}
   {toxinidir}/tools/deploy_rootwrap.sh {toxinidir} {envdir}/etc {envdir}/bin
-  stestr run --concurrency 4 {posargs}
+  stestr run --concurrency 3 {posargs}
 
 [testenv:dsvm-fullstack-gate]
 setenv = {[testenv:dsvm-fullstack]setenv}

zuul.d/base.yaml

@@ -24,6 +24,7 @@
       devstack_services:
         # Ignore any default set by devstack. Emit a "disable_all_services".
         base: false
+        etcd3: false
       devstack_localrc:
         INSTALL_TESTONLY_PACKAGES: true
         DATABASE_PASSWORD: stackdb