feat: add optional node-name field to hog scenarios with precedence over node-selector (#831)

Signed-off-by: Abhinav Sharma <abhinavs1920bpl@gmail.com>
Co-authored-by: Paige Patton <64206430+paigerube14@users.noreply.github.com>

krkn/scenario_plugins/hogs/hogs_scenario_plugin.py

@@ -25,6 +25,10 @@ class HogsScenarioPlugin(AbstractScenarioPlugin):
             with open(scenario, "r") as f:
                 scenario = yaml.full_load(f)
             scenario_config = HogConfig.from_yaml_dict(scenario)
+            
+            # Get node-name if provided
+            node_name = scenario.get('node-name')
+            
             has_selector = True
             if not scenario_config.node_selector or not re.match("^.+=.*$", scenario_config.node_selector):
                 if scenario_config.node_selector:
@@ -33,13 +37,19 @@ class HogsScenarioPlugin(AbstractScenarioPlugin):
             else:
                 node_selector = scenario_config.node_selector
 
-            available_nodes = lib_telemetry.get_lib_kubernetes().list_nodes(node_selector)
-            if len(available_nodes) == 0:
-                raise Exception("no available nodes to schedule workload")
+            if node_name:
+                logging.info(f"Using specific node: {node_name}")
+                all_nodes = lib_telemetry.get_lib_kubernetes().list_nodes("")
+                if node_name not in all_nodes:
+                    raise Exception(f"Specified node {node_name} not found or not available")
+                available_nodes = [node_name]
+            else:
+                available_nodes = lib_telemetry.get_lib_kubernetes().list_nodes(node_selector)
+                if len(available_nodes) == 0:
+                    raise Exception("no available nodes to schedule workload")
 
-            if not has_selector:
-                # if selector not specified picks a random node between the available
-                available_nodes = [available_nodes[random.randint(0, len(available_nodes))]]
+                if not has_selector:
+                    available_nodes = [available_nodes[random.randint(0, len(available_nodes))]]
 
             if scenario_config.number_of_nodes and len(available_nodes) > scenario_config.number_of_nodes:
                 available_nodes = random.sample(available_nodes, scenario_config.number_of_nodes)

scenarios/kube/cpu-hog.yml

@@ -5,6 +5,7 @@ image: quay.io/krkn-chaos/krkn-hog
 namespace: default
 cpu-load-percentage: 90
 cpu-method: all
+# node-name: "worker-0" # Uncomment to target a specific node by name
 node-selector: "node-role.kubernetes.io/worker="
 number-of-nodes: 2
 taints: [] #example ["node-role.kubernetes.io/master:NoSchedule"]

scenarios/kube/io-hog.yml

@@ -6,10 +6,11 @@ namespace: default
 io-block-size: 1m
 io-write-bytes: 1g
 io-target-pod-folder: /hog-data
+# node-name: "worker-0" # Uncomment to target a specific node by name
 io-target-pod-volume:
   name: node-volume
   hostPath:
     path: /root # a path writable by kubelet in the root filesystem of the node
 node-selector: "node-role.kubernetes.io/worker="
 number-of-nodes: ''
-taints: [] #example ["node-role.kubernetes.io/master:NoSchedule"]
+taints: [] #example ["node-role.kubernetes.io/master:NoSchedule"]    

scenarios/kube/memory-hog.yml

@@ -4,6 +4,7 @@ hog-type: memory
 image: quay.io/krkn-chaos/krkn-hog
 namespace: default
 memory-vm-bytes: 90%
+# node-name: "worker-0" # Uncomment to target a specific node by name
 node-selector: "node-role.kubernetes.io/worker="
 number-of-nodes: ''
 taints: [] #example ["node-role.kubernetes.io/master:NoSchedule"]