Ignoring unavailable shards during search request execution with igno…

CHANGELOG.md

@@ -44,6 +44,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - [BWC and API enforcement] Enforcing the presence of API annotations at build time ([#12872](https://github.com/opensearch-project/OpenSearch/pull/12872))
 - Improve built-in secure transports support ([#12907](https://github.com/opensearch-project/OpenSearch/pull/12907))
 - Update links to documentation in rest-api-spec ([#13043](https://github.com/opensearch-project/OpenSearch/pull/13043))
+- Ignoring unavailable shards during search request execution with ignore_available parameter ([#13298](https://github.com/opensearch-project/OpenSearch/pull/13298))
 - Refactoring globMatch using simpleMatchWithNormalizedStrings from Regex ([#13104](https://github.com/opensearch-project/OpenSearch/pull/13104))
 
 ### Deprecated

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

@@ -425,8 +425,10 @@ public final void executeNextPhase(SearchPhase currentPhase, SearchPhase nextPha
                             currentPhase.getName()
                         );
                     }
-                    onPhaseFailure(currentPhase, "Partial shards failure (" + discrepancy + " shards unavailable)", null);
-                    return;
+                    if (!request.indicesOptions().ignoreUnavailable()) {
+                        onPhaseFailure(currentPhase, "Partial shards failure (" + discrepancy + " shards unavailable)", null);
+                        return;
+                    }
                 }
             }
             if (logger.isTraceEnabled()) {

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

@@ -70,6 +70,7 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.EnumSet;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
@@ -442,6 +443,24 @@ public void testShardNotAvailableWithDisallowPartialFailures() {
         assertEquals(0, searchPhaseExecutionException.getSuppressed().length);
     }
 
+    public void testShardNotAvailableWithIgnoreUnavailable() {
+        SearchRequest searchRequest = new SearchRequest().allowPartialSearchResults(false)
+            .indicesOptions(new IndicesOptions(EnumSet.of(IndicesOptions.Option.IGNORE_UNAVAILABLE), IndicesOptions.WildcardStates.NONE));
+        AtomicReference<Exception> exception = new AtomicReference<>();
+        ActionListener<SearchResponse> listener = ActionListener.wrap(response -> {}, exception::set);
+        int numShards = randomIntBetween(2, 10);
+        ArraySearchPhaseResults<SearchPhaseResult> phaseResults = new ArraySearchPhaseResults<>(numShards);
+        AbstractSearchAsyncAction<SearchPhaseResult> action = createAction(searchRequest, phaseResults, listener, false, new AtomicLong());
+        // skip one to avoid the "all shards failed" failure.
+        SearchShardIterator skipIterator = new SearchShardIterator(null, null, Collections.emptyList(), null);
+        skipIterator.resetAndSkip();
+        action.skipShard(skipIterator);
+
+        // Validate no exception is thrown
+        action.executeNextPhase(action, createFetchSearchPhase());
+        action.sendSearchResponse(InternalSearchResponse.empty(), phaseResults.results);
+    }
+
     private static ArraySearchPhaseResults<SearchPhaseResult> phaseResults(
         Set<ShardSearchContextId> contextIds,
         List<Tuple<String, String>> nodeLookups,