diff --git a/.zuul.yaml b/.zuul.yaml
index 07136ea86de..1aac3831e91 100644
--- a/.zuul.yaml
+++ b/.zuul.yaml
@@ -124,6 +124,7 @@
       devstack_services:
         # Ignore any default set by devstack. Emit a "disable_all_services".
         base: false
+        etcd3: false
       devstack_localrc:
         USE_PYTHON3: true
         INSTALL_TESTONLY_PACKAGES: true
diff --git a/neutron/tests/fullstack/resources/config.py b/neutron/tests/fullstack/resources/config.py
index c255fa1ab42..3aa45350b0f 100644
--- a/neutron/tests/fullstack/resources/config.py
+++ b/neutron/tests/fullstack/resources/config.py
@@ -83,7 +83,7 @@ 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,
diff --git a/neutron/tests/fullstack/resources/environment.py b/neutron/tests/fullstack/resources/environment.py
index 9a57b84d60e..7e86034e73c 100644
--- a/neutron/tests/fullstack/resources/environment.py
+++ b/neutron/tests/fullstack/resources/environment.py
@@ -40,7 +40,7 @@ class EnvironmentDescription(object):
                  global_mtu=constants.DEFAULT_NETWORK_MTU,
                  debug_iptables=False, log=False, report_bandwidths=False,
                  has_placement=False, placement_port=None,
-                 ml2_extension_drivers=None):
+                 ml2_extension_drivers=None, api_workers=1):
         self.network_type = network_type
         self.l2_pop = l2_pop
         self.qos = qos
@@ -61,6 +61,7 @@ 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):
diff --git a/neutron/tests/fullstack/test_dhcp_agent.py b/neutron/tests/fullstack/test_dhcp_agent.py
index 339105c4f7f..7c6c6964afc 100644
--- a/neutron/tests/fullstack/test_dhcp_agent.py
+++ b/neutron/tests/fullstack/test_dhcp_agent.py
@@ -36,6 +36,7 @@ class BaseDhcpAgentTest(base.BaseFullStackTestCase):
         (constants.AGENT_TYPE_LINUXBRIDGE,
          {'l2_agent_type': constants.AGENT_TYPE_LINUXBRIDGE})
     ]
+    api_workers = 1
 
     def setUp(self):
         host_descriptions = [
@@ -48,7 +49,8 @@ class BaseDhcpAgentTest(base.BaseFullStackTestCase):
             environment.EnvironmentDescription(
                 l2_pop=False,
                 arp_responder=False,
-                agent_down_time=self.agent_down_time),
+                agent_down_time=self.agent_down_time,
+                api_workers=self.api_workers),
             host_descriptions)
 
         super(BaseDhcpAgentTest, self).setUp(env)
diff --git a/tox.ini b/tox.ini
index 5f702813c4c..3e7daf2ae89 100644
--- a/tox.ini
+++ b/tox.ini
@@ -96,7 +96,7 @@ 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:releasenotes]
 basepython = python3