Allow to specify how many compute nodes need to be used

Change-Id: I84ab43437b8c67ac19042233a28c552b8586560c

scenarios/networking/l2_dense.yaml

@@ -0,0 +1,21 @@
+description:
+  This scenario launches several pairs of VMs on pair of compute nodes.
+  VM are plugged into the same private network. Useful for testing performance
+  degradation when the number of VMs grows.
+
+deployment:
+  template: l2.hot
+  vm_accommodation: [pair, double_room, density: 8, compute_nodes: 2]
+
+execution:
+  size: 'quadratic_progression'
+  tests:
+  -
+    title: Iperf TCP test
+    class: iperf_graph
+    time: 60
+  -
+    title: Netperf TCP_STREAM
+    class: netperf
+    method: TCP_STREAM
+    time: 60

scenarios/networking/l2_double_density.yaml

@@ -1,20 +0,0 @@
-description:
-  This scenario launches pairs of VMs in the same private network. Every VM is
-  hosted on a separate compute node.
-
-deployment:
-  template: l2.hot
-  vm_accommodation: [pair, double_room, density: 2]
-
-execution:
-  size: 'linear_progression'
-  tests:
-  -
-    title: Iperf TCP test
-    class: iperf_graph
-    time: 60
-  -
-    title: Netperf TCP_STREAM
-    class: netperf
-    method: TCP_STREAM
-    time: 60

shaker/engine/deploy.py

@@ -27,12 +27,15 @@ LOG = logging.getLogger(__name__)
 
 
 def generate_agents(compute_nodes, vm_accommodation, unique):
-    cn_count = len(compute_nodes)
-    iterations = cn_count
-
+    density = 1
     for s in vm_accommodation:
-        if isinstance(s, dict) and s.get('density'):
-            iterations *= s.get('density')
+        if isinstance(s, dict):
+            density = s.get('density', 1)
+            if s.get('compute_nodes'):
+                compute_nodes = compute_nodes[:s.get('compute_nodes')]
+
+    cn_count = len(compute_nodes)
+    iterations = cn_count * density
 
     if 'single_room' in vm_accommodation and 'pair' in vm_accommodation:
         iterations //= 2

tests/test_deploy.py

@@ -141,6 +141,41 @@ class TestDeploy(testtools.TestCase):
                                         unique)
         self.assertEqual(expected, actual)
 
+    def test_generate_agents_alone_single_room_compute_nodes(self):
+        unique = 'UU1D'
+        expected = {
+            'UU1D_agent_0': {
+                'id': 'UU1D_agent_0',
+                'mode': 'alone',
+                'node': 'uno'},
+            'UU1D_agent_1': {
+                'id': 'UU1D_agent_1',
+                'mode': 'alone',
+                'node': 'duo'},
+        }
+        actual = deploy.generate_agents(['uno', 'duo', 'tre'],
+                                        ['single_room', {'compute_nodes': 2}],
+                                        unique)
+        self.assertEqual(expected, actual)
+
+    def test_generate_agents_alone_single_room_density_compute_nodes(self):
+        unique = 'UU1D'
+        expected = {
+            'UU1D_agent_0': {
+                'id': 'UU1D_agent_0',
+                'mode': 'alone',
+                'node': 'uno'},
+            'UU1D_agent_1': {
+                'id': 'UU1D_agent_1',
+                'mode': 'alone',
+                'node': 'uno'},
+        }
+        actual = deploy.generate_agents(['uno', 'duo', 'tre'],
+                                        ['single_room', {'compute_nodes': 1},
+                                         {'density': 2}],
+                                        unique)
+        self.assertEqual(expected, actual)
+
     def test_filter_agents_all_deployed(self):
         agents = {
             'UU1D_agent_0': {