Add successfulSearchShardIndices in searchRequestContext before onRequestEnd (opensearch-project#15967)

Signed-off-by: David Zane <davizane@amazon.com>
Signed-off-by: Ankit Jain <akjain@amazon.com>
Co-authored-by: Ankit Jain <akjain@amazon.com>

Author: dzane17

CHANGELOG.md

@@ -9,6 +9,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - [Workload Management] QueryGroup resource cancellation framework changes ([#15651](https://github.com/opensearch-project/OpenSearch/pull/15651))
 - Fallback to Remote cluster-state on Term-Version check mismatch - ([#15424](https://github.com/opensearch-project/OpenSearch/pull/15424))
 - Implement WithFieldName interface in ValuesSourceAggregationBuilder & FieldSortBuilder ([#15916](https://github.com/opensearch-project/OpenSearch/pull/15916))
+- Add successfulSearchShardIndices in searchRequestContext ([#15967](https://github.com/opensearch-project/OpenSearch/pull/15967))
 - Remove identity-related feature flagged code from the RestController ([#15430](https://github.com/opensearch-project/OpenSearch/pull/15430))
 
 ### Dependencies

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

@@ -754,6 +754,9 @@ public void sendSearchResponse(InternalSearchResponse internalSearchResponse, At
             }
             searchRequestContext.setTotalHits(internalSearchResponse.hits().getTotalHits());
             searchRequestContext.setShardStats(results.getNumShards(), successfulOps.get(), skippedOps.get(), failures.length);
+            searchRequestContext.setSuccessfulSearchShardIndices(
+                results.getSuccessfulResults().map(result -> result.getSearchShardTarget().getIndex()).collect(Collectors.toSet())
+            );
             onPhaseEnd(searchRequestContext);
             onRequestEnd(searchRequestContext);
             listener.onResponse(buildSearchResponse(internalSearchResponse, failures, scrollId, searchContextId));

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

@@ -20,6 +20,7 @@
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
+import java.util.Set;
 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.function.Supplier;
 
@@ -36,6 +37,7 @@ public class SearchRequestContext {
     private final Map<String, Long> phaseTookMap;
     private TotalHits totalHits;
     private final EnumMap<ShardStatsFieldNames, Integer> shardStats;
+    private Set<String> successfulSearchShardIndices;
 
     private final SearchRequest searchRequest;
     private final LinkedBlockingQueue<TaskResourceInfo> phaseResourceUsage;
@@ -141,6 +143,18 @@ public List<TaskResourceInfo> getPhaseResourceUsage() {
     public SearchRequest getRequest() {
         return searchRequest;
     }
+
+    void setSuccessfulSearchShardIndices(Set<String> successfulSearchShardIndices) {
+        this.successfulSearchShardIndices = successfulSearchShardIndices;
+    }
+
+    /**
+     * @return A {@link List} of {@link String} representing the names of the indices that were
+     * successfully queried at the shard level.
+     */
+    public Set<String> getSuccessfulSearchShardIndices() {
+        return successfulSearchShardIndices;
+    }
 }
 
 enum ShardStatsFieldNames {