Added Search Only strict routing setting (#17803)

vinaykpud · web-flow · commit ca03fdd206ba · 2025-04-08T11:12:45.000-07:00
* Added Search Only strict routing setting

Signed-off-by: Vinay Krishna Pudyodu &lt;vinkrish.neo@gmail.com&gt;

* Added Changelog

Signed-off-by: Vinay Krishna Pudyodu &lt;vinkrish.neo@gmail.com&gt;

---------

Signed-off-by: Vinay Krishna Pudyodu &lt;vinkrish.neo@gmail.com&gt;
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -26,6 +26,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Add GRPC DocumentService and Bulk endpoint ([#17727](https://github.com/opensearch-project/OpenSearch/pull/17727))
 - Added scale to zero (`search_only` mode) support for OpenSearch reader writer separation ([#17299](https://github.com/opensearch-project/OpenSearch/pull/17299)
 - [Star Tree] [Search] Resolving numeric range aggregation with metric aggregation using star-tree ([#17273](https://github.com/opensearch-project/OpenSearch/pull/17273))
+- Added Search Only strict routing setting ([#17803](https://github.com/opensearch-project/OpenSearch/pull/17803))
 
 ### Changed
 - Migrate BC libs to their FIPS counterparts ([#14912](https://github.com/opensearch-project/OpenSearch/pull/14912))
diff --git a/server/src/internalClusterTest/java/org/opensearch/indices/settings/SearchOnlyReplicaIT.java b/server/src/internalClusterTest/java/org/opensearch/indices/settings/SearchOnlyReplicaIT.java
@@ -8,6 +8,7 @@
 
 package org.opensearch.indices.settings;
 
+import org.opensearch.action.search.SearchPhaseExecutionException;
 import org.opensearch.action.search.SearchResponse;
 import org.opensearch.action.support.WriteRequest;
 import org.opensearch.cluster.ClusterState;
@@ -30,6 +31,8 @@
 import static org.opensearch.cluster.metadata.IndexMetadata.SETTING_REPLICATION_TYPE;
 import static org.opensearch.cluster.routing.UnassignedInfo.INDEX_DELAYED_NODE_LEFT_TIMEOUT_SETTING;
 import static org.opensearch.test.hamcrest.OpenSearchAssertions.assertHitCount;
+import static org.hamcrest.Matchers.anyOf;
+import static org.hamcrest.core.IsEqual.equalTo;
 
 @OpenSearchIntegTestCase.ClusterScope(scope = OpenSearchIntegTestCase.Scope.TEST, numDataNodes = 0)
 public class SearchOnlyReplicaIT extends RemoteStoreBaseIntegTestCase {
@@ -236,6 +239,80 @@ public void testSearchReplicaRoutingPreference() throws IOException {
         assertEquals(nodeId, indexShardRoutingTable.searchOnlyReplicas().get(0).currentNodeId());
     }
 
+    public void testSearchReplicaRoutingPreferenceWhenSearchReplicaUnassigned() {
+        internalCluster().startClusterManagerOnlyNode();
+        internalCluster().startDataOnlyNode();
+        createIndex(TEST_INDEX, Settings.builder().put(indexSettings()).put(IndexMetadata.SETTING_NUMBER_OF_SEARCH_REPLICAS, 1).build());
+        ensureYellow(TEST_INDEX);
+        client().prepareIndex(TEST_INDEX).setId("1").setSource("foo", "bar").setRefreshPolicy(WriteRequest.RefreshPolicy.IMMEDIATE).get();
+
+        // By default cluster.routing.search_only.strict is set as true
+        // When cluster.routing.search_only.strict is set as true, and no assigned search replica is available,
+        // search request will fail since it will route only to search replica but it's not available
+        Throwable throwable = assertThrows(
+            SearchPhaseExecutionException.class,
+            () -> client().prepareSearch(TEST_INDEX).setPreference(null).setQuery(QueryBuilders.matchAllQuery()).get()
+        );
+
+        assertEquals("all shards failed", throwable.getMessage());
+
+        // Set cluster.routing.search_only.strict as false
+        client().admin()
+            .cluster()
+            .prepareUpdateSettings()
+            .setTransientSettings(Settings.builder().put("cluster.routing.search_only.strict", false))
+            .get();
+
+        // When cluster.routing.search_only.strict is set as false, and no assigned search replica is available;
+        // search request will fall back to querying writers
+        SearchResponse response = client().prepareSearch(TEST_INDEX).setPreference(null).setQuery(QueryBuilders.matchAllQuery()).get();
+
+        String nodeId = response.getHits().getAt(0).getShard().getNodeId();
+        IndexShardRoutingTable indexShardRoutingTable = getIndexShardRoutingTable();
+        assertEquals(nodeId, indexShardRoutingTable.primaryShard().currentNodeId());
+    }
+
+    public void testSearchReplicaRoutingPreferenceWhenSearchReplicaAssigned() {
+        internalCluster().startClusterManagerOnlyNode();
+        internalCluster().startDataOnlyNode();
+        createIndex(TEST_INDEX, Settings.builder().put(indexSettings()).put(IndexMetadata.SETTING_NUMBER_OF_SEARCH_REPLICAS, 1).build());
+        ensureYellow(TEST_INDEX);
+        client().prepareIndex(TEST_INDEX).setId("1").setSource("foo", "bar").setRefreshPolicy(WriteRequest.RefreshPolicy.IMMEDIATE).get();
+
+        internalCluster().startSearchOnlyNode();
+        ensureGreen(TEST_INDEX);
+
+        // By default cluster.routing.search_only.strict is set as true
+        // When cluster.routing.search_only.strict is set as true, and assigned search replica is available;
+        // search request will succeed
+        SearchResponse response = client().prepareSearch(TEST_INDEX).setPreference(null).setQuery(QueryBuilders.matchAllQuery()).get();
+
+        String nodeId = response.getHits().getAt(0).getShard().getNodeId();
+        IndexShardRoutingTable indexShardRoutingTable = getIndexShardRoutingTable();
+        assertEquals(nodeId, indexShardRoutingTable.searchOnlyReplicas().get(0).currentNodeId());
+
+        // Set cluster.routing.search_only.strict as false
+        client().admin()
+            .cluster()
+            .prepareUpdateSettings()
+            .setTransientSettings(Settings.builder().put("cluster.routing.search_only.strict", false))
+            .get();
+
+        // When cluster.routing.search_only.strict is set as false, and assigned search replica is available;
+        // search request can land on either writer or reader
+        response = client().prepareSearch(TEST_INDEX).setPreference(null).setQuery(QueryBuilders.matchAllQuery()).get();
+
+        nodeId = response.getHits().getAt(0).getShard().getNodeId();
+        indexShardRoutingTable = getIndexShardRoutingTable();
+        assertThat(
+            nodeId,
+            anyOf(
+                equalTo(indexShardRoutingTable.primaryShard().currentNodeId()),
+                equalTo(indexShardRoutingTable.searchOnlyReplicas().get(0).currentNodeId())
+            )
+        );
+    }
+
     public void testUnableToAllocateSearchReplicaWontBlockRegularReplicaAllocation() {
         int numSearchReplicas = 1;
         int numWriterReplicas = 1;
diff --git a/server/src/main/java/org/opensearch/cluster/routing/OperationRouting.java b/server/src/main/java/org/opensearch/cluster/routing/OperationRouting.java
@@ -118,13 +118,21 @@ public class OperationRouting {
         Preference.PREFER_NODES
     );
 
+    public static final Setting<Boolean> STRICT_SEARCH_ONLY_ROUTING_ENABLED = Setting.boolSetting(
+        "cluster.routing.search_only.strict",
+        true,
+        Setting.Property.Dynamic,
+        Setting.Property.NodeScope
+    );
+
     private volatile List<String> awarenessAttributes;
     private volatile boolean useAdaptiveReplicaSelection;
     private volatile boolean ignoreAwarenessAttr;
     private volatile double weightedRoutingDefaultWeight;
     private volatile boolean isFailOpenEnabled;
     private volatile boolean isStrictWeightedShardRouting;
     private volatile boolean ignoreWeightedRouting;
+    private volatile boolean isStrictSearchOnlyShardRouting;
     private final boolean isReaderWriterSplitEnabled;
 
     public OperationRouting(Settings settings, ClusterSettings clusterSettings) {
@@ -140,12 +148,14 @@ public OperationRouting(Settings settings, ClusterSettings clusterSettings) {
         this.isFailOpenEnabled = WEIGHTED_ROUTING_FAILOPEN_ENABLED.get(settings);
         this.isStrictWeightedShardRouting = STRICT_WEIGHTED_SHARD_ROUTING_ENABLED.get(settings);
         this.ignoreWeightedRouting = IGNORE_WEIGHTED_SHARD_ROUTING.get(settings);
+        this.isStrictSearchOnlyShardRouting = STRICT_SEARCH_ONLY_ROUTING_ENABLED.get(settings);
         clusterSettings.addSettingsUpdateConsumer(USE_ADAPTIVE_REPLICA_SELECTION_SETTING, this::setUseAdaptiveReplicaSelection);
         clusterSettings.addSettingsUpdateConsumer(IGNORE_AWARENESS_ATTRIBUTES_SETTING, this::setIgnoreAwarenessAttributes);
         clusterSettings.addSettingsUpdateConsumer(WEIGHTED_ROUTING_DEFAULT_WEIGHT, this::setWeightedRoutingDefaultWeight);
         clusterSettings.addSettingsUpdateConsumer(WEIGHTED_ROUTING_FAILOPEN_ENABLED, this::setFailOpenEnabled);
         clusterSettings.addSettingsUpdateConsumer(STRICT_WEIGHTED_SHARD_ROUTING_ENABLED, this::setStrictWeightedShardRouting);
         clusterSettings.addSettingsUpdateConsumer(IGNORE_WEIGHTED_SHARD_ROUTING, this::setIgnoreWeightedRouting);
+        clusterSettings.addSettingsUpdateConsumer(STRICT_SEARCH_ONLY_ROUTING_ENABLED, this::setStrictSearchOnlyShardRouting);
         this.isReaderWriterSplitEnabled = FeatureFlags.READER_WRITER_SPLIT_EXPERIMENTAL_SETTING.get(settings);
     }
 
@@ -193,6 +203,10 @@ public double getWeightedRoutingDefaultWeight() {
         return this.weightedRoutingDefaultWeight;
     }
 
+    void setStrictSearchOnlyShardRouting(boolean strictSearchOnlyShardRouting) {
+        this.isStrictSearchOnlyShardRouting = strictSearchOnlyShardRouting;
+    }
+
     public ShardIterator indexShards(ClusterState clusterState, String index, String id, @Nullable String routing) {
         return shards(clusterState, index, id, routing).shardsIt();
     }
@@ -265,7 +279,7 @@ public GroupShardsIterator<ShardIterator> searchShards(
 
             if (isReaderWriterSplitEnabled) {
                 if (preference == null || preference.isEmpty()) {
-                    if (indexMetadataForShard.getNumberOfSearchOnlyReplicas() > 0) {
+                    if (indexMetadataForShard.getNumberOfSearchOnlyReplicas() > 0 && isStrictSearchOnlyShardRouting) {
                         preference = Preference.SEARCH_REPLICA.type();
                     }
                 }
diff --git a/server/src/main/java/org/opensearch/common/settings/ClusterSettings.java b/server/src/main/java/org/opensearch/common/settings/ClusterSettings.java
@@ -613,6 +613,7 @@ public void apply(Settings value, Settings current, Settings previous) {
                 OperationRouting.WEIGHTED_ROUTING_FAILOPEN_ENABLED,
                 OperationRouting.STRICT_WEIGHTED_SHARD_ROUTING_ENABLED,
                 OperationRouting.IGNORE_WEIGHTED_SHARD_ROUTING,
+                OperationRouting.STRICT_SEARCH_ONLY_ROUTING_ENABLED,
                 IndexGraveyard.SETTING_MAX_TOMBSTONES,
                 PersistentTasksClusterService.CLUSTER_TASKS_ALLOCATION_RECHECK_INTERVAL_SETTING,
                 EnableAssignmentDecider.CLUSTER_TASKS_ALLOCATION_ENABLE_SETTING,
diff --git a/server/src/test/java/org/opensearch/cluster/routing/OperationRoutingTests.java b/server/src/test/java/org/opensearch/cluster/routing/OperationRoutingTests.java
@@ -1196,6 +1196,77 @@ public void testSearchReplicaDefaultRouting() throws Exception {
         }
     }
 
+    public void testSearchReplicaRoutingWhenSearchOnlyStrictSettingIsFalse() throws Exception {
+        final int numShards = 1;
+        final int numReplicas = 2;
+        final int numSearchReplicas = 2;
+        final String indexName = "test";
+        final String[] indexNames = new String[] { indexName };
+
+        ClusterService clusterService = null;
+        ThreadPool threadPool = null;
+
+        try {
+            OperationRouting opRouting = new OperationRouting(
+                Settings.builder().put(FeatureFlags.READER_WRITER_SPLIT_EXPERIMENTAL, "true").build(),
+                new ClusterSettings(Settings.EMPTY, ClusterSettings.BUILT_IN_CLUSTER_SETTINGS)
+            );
+            opRouting.setStrictSearchOnlyShardRouting(false);
+
+            ClusterState state = ClusterStateCreationUtils.stateWithAssignedPrimariesAndReplicas(
+                indexNames,
+                numShards,
+                numReplicas,
+                numSearchReplicas
+            );
+            IndexShardRoutingTable indexShardRoutingTable = state.getRoutingTable().index(indexName).getShards().get(0);
+            ShardId shardId = indexShardRoutingTable.searchOnlyReplicas().get(0).shardId();
+
+            threadPool = new TestThreadPool("testSearchReplicaDefaultRouting");
+            clusterService = ClusterServiceUtils.createClusterService(threadPool);
+
+            // add a search replica in initializing state:
+            DiscoveryNode node = new DiscoveryNode(
+                "node_initializing",
+                OpenSearchTestCase.buildNewFakeTransportAddress(),
+                Collections.emptyMap(),
+                new HashSet<>(DiscoveryNodeRole.BUILT_IN_ROLES),
+                Version.CURRENT
+            );
+
+            IndexMetadata indexMetadata = IndexMetadata.builder(indexName)
+                .settings(Settings.builder().put(state.metadata().index(indexName).getSettings()).build())
+                .numberOfSearchReplicas(3)
+                .numberOfReplicas(2)
+                .build();
+            Metadata.Builder metadataBuilder = Metadata.builder(state.metadata()).put(indexMetadata, false).generateClusterUuidIfNeeded();
+            IndexRoutingTable.Builder indexShardRoutingBuilder = IndexRoutingTable.builder(indexMetadata.getIndex());
+            indexShardRoutingBuilder.addIndexShard(indexShardRoutingTable);
+            indexShardRoutingBuilder.addShard(
+                TestShardRouting.newShardRouting(shardId, node.getId(), null, false, true, ShardRoutingState.INITIALIZING, null)
+            );
+            state = ClusterState.builder(state)
+                .routingTable(RoutingTable.builder().add(indexShardRoutingBuilder).build())
+                .metadata(metadataBuilder.build())
+                .build();
+
+            GroupShardsIterator<ShardIterator> groupIterator = opRouting.searchShards(state, indexNames, null, null);
+            assertThat("one group per shard", groupIterator.size(), equalTo(numShards));
+            for (ShardIterator shardIterator : groupIterator) {
+                assertEquals("We should have all 6 shards returned", shardIterator.size(), 6);
+                for (ShardRouting shardRouting : shardIterator) {
+                    assertTrue(
+                        "Any shard can exist with when cluster.routing.search_only.strict is set as false",
+                        shardRouting.isSearchOnly() || shardRouting.primary() || shardRouting.isSearchOnly() == false
+                    );
+                }
+            }
+        } finally {
+            IOUtils.close(clusterService);
+            terminate(threadPool);
+        }
+    }
+
     private DiscoveryNode[] setupNodes() {
         // Sets up two data nodes in zone-a and one data node in zone-b
         List<String> zones = Arrays.asList("a", "a", "b");
