fix(FullScan): choose only non-disruptive node

this commit has the following changes

1 introduce common targed_node_lock mechanism
that can be used in nemesis and Scan operations

2 FullScan operation now run only on free of nemeses node

3 change all node.running_nemesis settings to use common methods
set/unset_running_nemesis from common targed_node_lock file (except unit tests)

fixes: scylladb#9284

sdcm/cluster.py

@@ -32,7 +32,6 @@
 import itertools
 import json
 import ipaddress
-from importlib import import_module
 from typing import List, Optional, Dict, Union, Set, Iterable, ContextManager, Any, IO, AnyStr, Callable
 from datetime import datetime, timezone
 from textwrap import dedent
@@ -66,6 +65,7 @@
 from sdcm.mgmt.common import get_manager_repo_from_defaults, get_manager_scylla_backend
 from sdcm.prometheus import start_metrics_server, PrometheusAlertManagerListener, AlertSilencer
 from sdcm.log import SDCMAdapter
+from sdcm.target_node_lock import run_nemesis
 from sdcm.provision.common.configuration_script import ConfigurationScriptBuilder
 from sdcm.provision.common.utils import disable_daily_apt_triggers
 from sdcm.provision.scylla_yaml import ScyllaYamlNodeAttrBuilder
@@ -4579,9 +4579,7 @@ def _rotate_kms_key(kms_key_alias_name, kms_key_rotation_interval, db_cluster):
                         message=f"Failed to rotate AWS KMS key for the '{kms_key_alias_name}' alias",
                         traceback=traceback.format_exc()).publish()
                 try:
-                    nemesis_class = self.nemesis[0] if self.nemesis else getattr(
-                        import_module('sdcm.nemesis'), "Nemesis")
-                    with nemesis_class.run_nemesis(node_list=db_cluster.data_nodes, nemesis_label="KMS encryption check") as target_node:
+                    with run_nemesis(node_list=db_cluster.data_nodes, nemesis_label="KMS encryption check") as target_node:
                         self.log.debug("Target node for 'rotate_kms_key' is %s", target_node.name)
 
                         ks_cf_list = db_cluster.get_non_system_ks_cf_list(

sdcm/kcl_thread.py

@@ -21,7 +21,7 @@
 from functools import cached_property
 from typing import Dict
 
-from sdcm.nemesis import Nemesis
+from sdcm.target_node_lock import run_nemesis
 from sdcm.stress_thread import DockerBasedStressThread
 from sdcm.stress.base import format_stress_cmd_error
 from sdcm.utils.docker_remote import RemoteDocker
@@ -132,7 +132,7 @@ def _run_stress(self, loader, loader_idx, cpu_idx):
             end_time = time.time() + self._timeout
 
             while not self._stop_event.is_set():
-                with Nemesis.run_nemesis(node_list=self.node_list, nemesis_label="Compare tables size by cf-stats") as node:
+                with run_nemesis(node_list=self.node_list, nemesis_label="Compare tables size by cf-stats") as node:
                     node.run_nodetool('flush')
 
                     dst_size = node.get_cfstats(dst_table)['Number of partitions (estimate)']

sdcm/nemesis.py

@@ -30,7 +30,7 @@
 import json
 import itertools
 from distutils.version import LooseVersion
-from contextlib import ExitStack, contextmanager
+from contextlib import ExitStack
 from typing import Any, List, Optional, Type, Tuple, Callable, Dict, Set, Union, Iterable
 from functools import wraps, partial
 from collections import defaultdict, Counter, namedtuple
@@ -65,6 +65,7 @@
 )
 from sdcm.db_stats import PrometheusDBStats
 from sdcm.log import SDCMAdapter
+from sdcm.target_node_lock import run_nemesis, set_running_nemesis, unset_running_nemesis, NEMESIS_TARGET_SELECTION_LOCK
 from sdcm.logcollector import save_kallsyms_map
 from sdcm.mgmt.common import TaskStatus, ScyllaManagerError, get_persistent_snapshots
 from sdcm.nemesis_publisher import NemesisElasticSearchPublisher
@@ -170,8 +171,6 @@
     "disrupt_terminate_kubernetes_host_then_decommission_and_add_scylla_node",
 )
 
-NEMESIS_TARGET_SELECTION_LOCK = Lock()
-
 
 class DefaultValue:  # pylint: disable=too-few-public-methods
     """
@@ -337,24 +336,6 @@ def wrapper(self, *args, **kwargs):
         setattr(cls, func.__name__, wrapper)  # bind it to Nemesis class
         return func  # returning func means func can still be used normally
 
-    @staticmethod
-    @contextmanager
-    def run_nemesis(node_list: list['BaseNode'], nemesis_label: str):
-        """
-        pick a node out of a `node_list`, and mark is as running_nemesis
-        for the duration of this context
-        """
-        with NEMESIS_TARGET_SELECTION_LOCK:
-            free_nodes = [node for node in node_list if not node.running_nemesis]
-            assert free_nodes, f"couldn't find nodes for running:`{nemesis_label}`, are all nodes running nemesis ?"
-            node = random.choice(free_nodes)
-            node.running_nemesis = nemesis_label
-        try:
-            yield node
-        finally:
-            with NEMESIS_TARGET_SELECTION_LOCK:
-                node.running_nemesis = None
-
     def use_nemesis_seed(self):
         if nemesis_seed := self.tester.params.get("nemesis_seed"):
             random.seed(nemesis_seed)
@@ -381,14 +362,11 @@ def publish_event(self, disrupt, status=True, data=None):
         DisruptionEvent(nemesis_name=disrupt, severity=severity, **data).publish()
 
     def set_current_running_nemesis(self, node):
-        with NEMESIS_TARGET_SELECTION_LOCK:
-            node.running_nemesis = self.current_disruption
+        set_running_nemesis(node, self.current_disruption)
 
     @staticmethod
     def unset_current_running_nemesis(node):
-        if node is not None:
-            with NEMESIS_TARGET_SELECTION_LOCK:
-                node.running_nemesis = None
+        unset_running_nemesis(node)
 
     def set_target_node_pool(self, nodelist: list[BaseNode] | None = None):
         """Set pool of nodes to choose target node """
@@ -453,10 +431,10 @@ def set_target_node(self, dc_idx: Optional[int] = None, rack: Optional[int] = No
                 self.target_node = random.choice(nodes)
 
             if current_disruption:
-                self.target_node.running_nemesis = current_disruption
+                set_running_nemesis(self.target_node, current_disruption)
                 self.set_current_disruption(current_disruption)
             elif self.current_disruption:
-                self.target_node.running_nemesis = self.current_disruption
+                set_running_nemesis(self.target_node, self.current_disruption)
             else:
                 raise ValueError("current_disruption is not set")
             self.log.info('Current Target: %s with running nemesis: %s',
@@ -4046,7 +4024,7 @@ def decommission_post_action():
                     terminate_pattern.timeout):
                 stack.enter_context(expected_start_failed_context)
             with ignore_stream_mutation_fragments_errors(), ignore_raft_topology_cmd_failing(), \
-                self.run_nemesis(node_list=self.cluster.data_nodes, nemesis_label="DecommissionStreamingErr") as verification_node, \
+                run_nemesis(node_list=self.cluster.data_nodes, nemesis_label="DecommissionStreamingErr") as verification_node, \
                 FailedDecommissionOperationMonitoring(target_node=self.target_node,
                                                       verification_node=verification_node,
                                                       timeout=full_operations_timeout):
@@ -5240,7 +5218,7 @@ def disrupt_bootstrap_streaming_error(self):
             decommission_timeout = 7200
             monitoring_decommission_timeout = decommission_timeout + 100
             un_nodes = self.cluster.get_nodes_up_and_normal()
-            with Nemesis.run_nemesis(node_list=un_nodes, nemesis_label="BootstrapStreaminError") as verification_node, \
+            with run_nemesis(node_list=un_nodes, nemesis_label="BootstrapStreaminError") as verification_node, \
                     FailedDecommissionOperationMonitoring(target_node=new_node, verification_node=verification_node,
                                                           timeout=monitoring_decommission_timeout):