Improve the rejection logic for soft mode query groups during node du…

…ress (#16417)

* improve the rejection logic for wlm

Signed-off-by: Kaushal Kumar <ravi.kaushal97@gmail.com>

* add CHANGELOG

Signed-off-by: Kaushal Kumar <ravi.kaushal97@gmail.com>

---------

Signed-off-by: Kaushal Kumar <ravi.kaushal97@gmail.com>

CHANGELOG.md

@@ -93,6 +93,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Fix missing fields in task index mapping to ensure proper task result storage ([#16201](https://github.com/opensearch-project/OpenSearch/pull/16201))
 - Fix typo super->sb in method toString() of RemoteStoreNodeAttribute ([#15362](https://github.com/opensearch-project/OpenSearch/pull/15362))
 - Fix array hashCode calculation in ResyncReplicationRequest ([#16378](https://github.com/opensearch-project/OpenSearch/pull/16378))
+- [Workload Management] Enhance rejection mechanism in workload management ([#16417](https://github.com/opensearch-project/OpenSearch/pull/16417))
 
 ### Security
 

server/src/main/java/org/opensearch/wlm/QueryGroupService.java

@@ -266,11 +266,12 @@ public void rejectIfNeeded(String queryGroupId) {
             return;
         }
 
-        // rejections will not happen for SOFT mode QueryGroups
+        // rejections will not happen for SOFT mode QueryGroups unless node is in duress
         Optional<QueryGroup> optionalQueryGroup = activeQueryGroups.stream().filter(x -> x.get_id().equals(queryGroupId)).findFirst();
 
-        if (optionalQueryGroup.isPresent() && optionalQueryGroup.get().getResiliencyMode() == MutableQueryGroupFragment.ResiliencyMode.SOFT)
-            return;
+        if (optionalQueryGroup.isPresent()
+            && (optionalQueryGroup.get().getResiliencyMode() == MutableQueryGroupFragment.ResiliencyMode.SOFT
+                && !nodeDuressTrackers.isNodeInDuress())) return;
 
         optionalQueryGroup.ifPresent(queryGroup -> {
             boolean reject = false;

server/src/test/java/org/opensearch/wlm/QueryGroupServiceTests.java

@@ -48,6 +48,7 @@
 import static org.mockito.Mockito.when;
 
 public class QueryGroupServiceTests extends OpenSearchTestCase {
+    public static final String QUERY_GROUP_ID = "queryGroupId1";
     private QueryGroupService queryGroupService;
     private QueryGroupTaskCancellationService mockCancellationService;
     private ClusterService mockClusterService;
@@ -68,6 +69,7 @@ public void setUp() throws Exception {
         mockNodeDuressTrackers = Mockito.mock(NodeDuressTrackers.class);
         mockCancellationService = Mockito.mock(TestQueryGroupCancellationService.class);
         mockQueryGroupsStateAccessor = new QueryGroupsStateAccessor();
+        when(mockNodeDuressTrackers.isNodeInDuress()).thenReturn(false);
 
         queryGroupService = new QueryGroupService(
             mockCancellationService,
@@ -203,26 +205,52 @@ public void testRejectIfNeeded_whenQueryGroupIdIsNullOrDefaultOne() {
         verify(spyMap, never()).get(any());
     }
 
+    public void testRejectIfNeeded_whenSoftModeQueryGroupIsContendedAndNodeInDuress() {
+        Set<QueryGroup> activeQueryGroups = getActiveQueryGroups(
+            "testQueryGroup",
+            QUERY_GROUP_ID,
+            MutableQueryGroupFragment.ResiliencyMode.SOFT,
+            Map.of(ResourceType.CPU, 0.10)
+        );
+        mockQueryGroupStateMap = new HashMap<>();
+        mockQueryGroupStateMap.put("queryGroupId1", new QueryGroupState());
+        QueryGroupState state = new QueryGroupState();
+        QueryGroupState.ResourceTypeState cpuResourceState = new QueryGroupState.ResourceTypeState(ResourceType.CPU);
+        cpuResourceState.setLastRecordedUsage(0.10);
+        state.getResourceState().put(ResourceType.CPU, cpuResourceState);
+        QueryGroupState spyState = spy(state);
+        mockQueryGroupStateMap.put(QUERY_GROUP_ID, spyState);
+
+        mockQueryGroupsStateAccessor = new QueryGroupsStateAccessor(mockQueryGroupStateMap);
+
+        queryGroupService = new QueryGroupService(
+            mockCancellationService,
+            mockClusterService,
+            mockThreadPool,
+            mockWorkloadManagementSettings,
+            mockNodeDuressTrackers,
+            mockQueryGroupsStateAccessor,
+            activeQueryGroups,
+            new HashSet<>()
+        );
+        when(mockWorkloadManagementSettings.getWlmMode()).thenReturn(WlmMode.ENABLED);
+        when(mockNodeDuressTrackers.isNodeInDuress()).thenReturn(true);
+        assertThrows(OpenSearchRejectedExecutionException.class, () -> queryGroupService.rejectIfNeeded("queryGroupId1"));
+    }
+
     public void testRejectIfNeeded_whenQueryGroupIsSoftMode() {
-        QueryGroup testQueryGroup = new QueryGroup(
+        Set<QueryGroup> activeQueryGroups = getActiveQueryGroups(
             "testQueryGroup",
-            "queryGroupId1",
-            new MutableQueryGroupFragment(MutableQueryGroupFragment.ResiliencyMode.SOFT, Map.of(ResourceType.CPU, 0.10)),
-            1L
+            QUERY_GROUP_ID,
+            MutableQueryGroupFragment.ResiliencyMode.SOFT,
+            Map.of(ResourceType.CPU, 0.10)
         );
-        Set<QueryGroup> activeQueryGroups = new HashSet<>() {
-            {
-                add(testQueryGroup);
-            }
-        };
         mockQueryGroupStateMap = new HashMap<>();
         QueryGroupState spyState = spy(new QueryGroupState());
         mockQueryGroupStateMap.put("queryGroupId1", spyState);
 
         mockQueryGroupsStateAccessor = new QueryGroupsStateAccessor(mockQueryGroupStateMap);
 
-        Map<String, QueryGroupState> spyMap = spy(mockQueryGroupStateMap);
-
         queryGroupService = new QueryGroupService(
             mockCancellationService,
             mockClusterService,
@@ -239,11 +267,11 @@ public void testRejectIfNeeded_whenQueryGroupIsSoftMode() {
     }
 
     public void testRejectIfNeeded_whenQueryGroupIsEnforcedMode_andNotBreaching() {
-        QueryGroup testQueryGroup = new QueryGroup(
+        QueryGroup testQueryGroup = getQueryGroup(
             "testQueryGroup",
             "queryGroupId1",
-            new MutableQueryGroupFragment(MutableQueryGroupFragment.ResiliencyMode.ENFORCED, Map.of(ResourceType.CPU, 0.10)),
-            1L
+            MutableQueryGroupFragment.ResiliencyMode.ENFORCED,
+            Map.of(ResourceType.CPU, 0.10)
         );
         QueryGroup spuQueryGroup = spy(testQueryGroup);
         Set<QueryGroup> activeQueryGroups = new HashSet<>() {
@@ -464,6 +492,31 @@ public void testShouldSBPHandle() {
 
     }
 
+    private static Set<QueryGroup> getActiveQueryGroups(
+        String name,
+        String id,
+        MutableQueryGroupFragment.ResiliencyMode mode,
+        Map<ResourceType, Double> resourceLimits
+    ) {
+        QueryGroup testQueryGroup = getQueryGroup(name, id, mode, resourceLimits);
+        Set<QueryGroup> activeQueryGroups = new HashSet<>() {
+            {
+                add(testQueryGroup);
+            }
+        };
+        return activeQueryGroups;
+    }
+
+    private static QueryGroup getQueryGroup(
+        String name,
+        String id,
+        MutableQueryGroupFragment.ResiliencyMode mode,
+        Map<ResourceType, Double> resourceLimits
+    ) {
+        QueryGroup testQueryGroup = new QueryGroup(name, id, new MutableQueryGroupFragment(mode, resourceLimits), 1L);
+        return testQueryGroup;
+    }
+
     // This is needed to test the behavior of QueryGroupService#doRun method
     static class TestQueryGroupCancellationService extends QueryGroupTaskCancellationService {
         public TestQueryGroupCancellationService(