[Backport 2.x] Fix issue when calling Delete PIT endpoint and no PITs exist

CHANGELOG.md

@@ -113,6 +113,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Fix for stuck update action in a bulk with `retry_on_conflict` property ([#11152](https://github.com/opensearch-project/OpenSearch/issues/11152))
 - Fix template setting override for replication type ([#11417](https://github.com/opensearch-project/OpenSearch/pull/11417))
 - Fix Automatic addition of protocol broken in #11512 ([#11609](https://github.com/opensearch-project/OpenSearch/pull/11609))
+- Fix issue when calling Delete PIT endpoint and no PITs exist ([#11711](https://github.com/opensearch-project/OpenSearch/pull/11711))
 
 ### Security
 

server/src/main/java/org/opensearch/action/search/PitService.java

@@ -71,6 +71,7 @@ public void deletePitContexts(
     ) {
         if (nodeToContextsMap.size() == 0) {
             listener.onResponse(new DeletePitResponse(Collections.emptyList()));
+            return;
         }
         final Set<String> clusters = nodeToContextsMap.values()
             .stream()

server/src/test/java/org/opensearch/action/search/TransportDeletePitActionTests.java

@@ -21,6 +21,7 @@
 import org.opensearch.common.settings.Settings;
 import org.opensearch.core.action.ActionListener;
 import org.opensearch.core.common.io.stream.NamedWriteableRegistry;
+import org.opensearch.core.rest.RestStatus;
 import org.opensearch.core.tasks.TaskId;
 import org.opensearch.index.query.IdsQueryBuilder;
 import org.opensearch.index.query.MatchAllQueryBuilder;
@@ -33,6 +34,7 @@
 import org.opensearch.threadpool.ThreadPool;
 import org.opensearch.transport.RemoteClusterConnectionTests;
 import org.opensearch.transport.Transport;
+import org.opensearch.transport.TransportService;
 import org.junit.Before;
 
 import java.util.ArrayList;
@@ -262,6 +264,46 @@ public void getAllPits(ActionListener<GetAllPitNodesResponse> getAllPitsListener
         }
     }
 
+    public void testDeleteAllPITSuccessWhenNoPITsExist() throws InterruptedException, ExecutionException {
+        ActionFilters actionFilters = mock(ActionFilters.class);
+        when(actionFilters.filters()).thenReturn(new ActionFilter[0]);
+        List<DiscoveryNode> knownNodes = new CopyOnWriteArrayList<>();
+        try (MockTransportService cluster1Transport = startTransport("cluster_1_node", knownNodes, Version.CURRENT)) {
+            knownNodes.add(cluster1Transport.getLocalDiscoNode());
+            TransportService mockTransportService = mock(TransportService.class);
+            PitService pitService = new PitService(clusterServiceMock, mock(SearchTransportService.class), mockTransportService, client) {
+                @Override
+                public void getAllPits(ActionListener<GetAllPitNodesResponse> getAllPitsListener) {
+                    List<ListPitInfo> list = new ArrayList<>();
+                    GetAllPitNodeResponse getAllPitNodeResponse = new GetAllPitNodeResponse(cluster1Transport.getLocalDiscoNode(), list);
+                    List<GetAllPitNodeResponse> nodeList = new ArrayList();
+                    nodeList.add(getAllPitNodeResponse);
+                    getAllPitsListener.onResponse(new GetAllPitNodesResponse(new ClusterName("cn"), nodeList, new ArrayList()));
+                }
+            };
+            TransportDeletePitAction action = new TransportDeletePitAction(
+                mockTransportService,
+                actionFilters,
+                namedWriteableRegistry,
+                pitService
+            );
+            DeletePitRequest deletePITRequest = new DeletePitRequest("_all");
+            ActionListener<DeletePitResponse> listener = new ActionListener<DeletePitResponse>() {
+                @Override
+                public void onResponse(DeletePitResponse deletePitResponse) {
+                    assertEquals(RestStatus.OK, deletePitResponse.status());
+                    assertEquals(0, deletePitResponse.getDeletePitResults().size());
+                }
+
+                @Override
+                public void onFailure(Exception e) {
+                    fail("Should not receive Exception");
+                }
+            };
+            action.execute(task, deletePITRequest, listener);
+        }
+    }
+
     public void testDeletePitWhenNodeIsDown() throws InterruptedException, ExecutionException {
         List<DiscoveryNode> deleteNodesInvoked = new CopyOnWriteArrayList<>();
         ActionFilters actionFilters = mock(ActionFilters.class);