Avoid dividing zero

Some flavors may set disk size 0 byte, so disk_capacity may be 0.

Change-Id: I0f2cfd5ce9f64cd94e7b6ded7865384cb2b1e190
Closes-Bug: #1517033

watcher/decision_engine/strategies/basic_consolidation.py

@@ -233,8 +233,12 @@ class BasicConsolidation(Strategy):
         score_cores = (1 - (float(cpu_capacity) - float(total_cores_used)) /
                        float(cpu_capacity))
 
-        score_disk = (1 - (float(disk_capacity) - float(total_disk_used)) /
-                      float(disk_capacity))
+        # It's possible that disk_capacity is 0, e.g. m1.nano.disk = 0
+        if disk_capacity == 0:
+            score_disk = 0
+        else:
+            score_disk = (1 - (float(disk_capacity) - float(total_disk_used)) /
+                          float(disk_capacity))
 
         score_memory = (
             1 - (float(memory_capacity) - float(total_memory_used)) /

watcher/tests/decision_engine/faker_cluster_state.py

@@ -336,3 +336,49 @@ class FakerStateCollector(ClusterStateCollector):
             current_state_cluster.add_hypervisor(node)
 
         return current_state_cluster
+
+    def generate_scenario_5_with_vm_disk_0(self):
+        vms = []
+        current_state_cluster = ModelRoot()
+        # number of nodes
+        count_node = 1
+        # number of vms
+        count_vm = 1
+
+        # define ressouce ( CPU, MEM disk, ... )
+        mem = Resource(ResourceType.memory)
+        # 2199.954 Mhz
+        num_cores = Resource(ResourceType.cpu_cores)
+        disk = Resource(ResourceType.disk)
+
+        current_state_cluster.create_resource(mem)
+        current_state_cluster.create_resource(num_cores)
+        current_state_cluster.create_resource(disk)
+
+        for i in range(0, count_node):
+            node_uuid = "Node_" + str(i)
+            node = Hypervisor()
+            node.uuid = node_uuid
+
+            mem.set_capacity(node, 4)
+            disk.set_capacity(node, 4)
+            num_cores.set_capacity(node, 4)
+            # print("create "+str(node))
+            current_state_cluster.add_hypervisor(node)
+
+        for i in range(0, count_vm):
+            vm_uuid = "VM_" + str(i)
+            vm = VM()
+            vm.uuid = vm_uuid
+            # print("create "+str(vm))
+            mem.set_capacity(vm, 2)
+            disk.set_capacity(vm, 0)
+            num_cores.set_capacity(vm, 4)
+            vms.append(vm)
+            current_state_cluster.add_vm(vm)
+
+        current_state_cluster.get_mapping().map(
+            current_state_cluster.get_hypervisor_from_id("Node_0"),
+            current_state_cluster.get_vm_from_id("VM_0"))
+
+        return current_state_cluster

watcher/tests/decision_engine/strategies/test_basic_consolidation.py

@@ -92,6 +92,14 @@ class TestBasicConsolidation(base.BaseTestCase):
         vm_7_score = 0.0
         self.assertEqual(sercon.calculate_score_vm(vm_7, cluster), vm_7_score)
 
+    def test_basic_consolidation_score_vm_disk(self):
+        cluster = self.fake_cluster.generate_scenario_5_with_vm_disk_0()
+        sercon = BasicConsolidation()
+        sercon.set_metrics_resource_collector(self.fake_metrics)
+        vm_0 = cluster.get_vm_from_id("VM_0")
+        vm_0_score = 0.0
+        self.assertEqual(sercon.calculate_score_vm(vm_0, cluster), vm_0_score)
+
     def test_basic_consolidation_weight(self):
         cluster = self.fake_cluster.generate_scenario_1()
         sercon = BasicConsolidation()