[Segment Replication] Add ClusterState utility to identify SEGMENT replication (#9593)

* [Segment Replication] Add ClusterState utility to identify SEGMENT replication

Signed-off-by: Suraj Singh <surajrider@gmail.com>

* Address review comment

Signed-off-by: Suraj Singh <surajrider@gmail.com>

* Address review comments

Signed-off-by: Suraj Singh <surajrider@gmail.com>

---------

Signed-off-by: Suraj Singh <surajrider@gmail.com>

Author: dreamer-89

server/src/main/java/org/opensearch/action/get/TransportGetAction.java

@@ -36,7 +36,6 @@
 import org.opensearch.action.support.ActionFilters;
 import org.opensearch.action.support.single.shard.TransportSingleShardAction;
 import org.opensearch.cluster.ClusterState;
-import org.opensearch.cluster.metadata.IndexMetadata;
 import org.opensearch.cluster.metadata.IndexNameExpressionResolver;
 import org.opensearch.cluster.routing.Preference;
 import org.opensearch.cluster.routing.ShardIterator;
@@ -49,12 +48,10 @@
 import org.opensearch.index.get.GetResult;
 import org.opensearch.index.shard.IndexShard;
 import org.opensearch.indices.IndicesService;
-import org.opensearch.indices.replication.common.ReplicationType;
 import org.opensearch.threadpool.ThreadPool;
 import org.opensearch.transport.TransportService;
 
 import java.io.IOException;
-import java.util.Optional;
 
 /**
  * Performs the get operation.
@@ -92,20 +89,11 @@ protected boolean resolveIndex(GetRequest request) {
         return true;
     }
 
-    static boolean isSegmentReplicationEnabled(ClusterState state, String indexName) {
-        return Optional.ofNullable(state.getMetadata().index(indexName))
-            .map(
-                indexMetadata -> ReplicationType.parseString(indexMetadata.getSettings().get(IndexMetadata.SETTING_REPLICATION_TYPE))
-                    .equals(ReplicationType.SEGMENT)
-            )
-            .orElse(false);
-    }
-
     /**
      * Returns true if GET request should be routed to primary shards, else false.
      */
     protected static boolean shouldForcePrimaryRouting(ClusterState state, boolean realtime, String preference, String indexName) {
-        return isSegmentReplicationEnabled(state, indexName) && realtime && preference == null;
+        return state.isSegmentReplicationEnabled(indexName) && realtime && preference == null;
     }
 
     @Override

server/src/main/java/org/opensearch/cluster/ClusterState.java

@@ -61,6 +61,7 @@
 import org.opensearch.core.xcontent.ToXContentFragment;
 import org.opensearch.core.xcontent.XContentBuilder;
 import org.opensearch.discovery.Discovery;
+import org.opensearch.indices.replication.common.ReplicationType;
 
 import java.io.IOException;
 import java.util.Collections;
@@ -409,6 +410,21 @@ public boolean supersedes(ClusterState other) {
 
     }
 
+    /**
+     * Utility to identify whether input index belongs to SEGMENT replication in established cluster state.
+     *
+     * @param indexName Index name
+     * @return true if index belong SEGMENT replication, false otherwise
+     */
+    public boolean isSegmentReplicationEnabled(String indexName) {
+        return Optional.ofNullable(this.getMetadata().index(indexName))
+            .map(
+                indexMetadata -> ReplicationType.parseString(indexMetadata.getSettings().get(IndexMetadata.SETTING_REPLICATION_TYPE))
+                    .equals(ReplicationType.SEGMENT)
+            )
+            .orElse(false);
+    }
+
     /**
      * Metrics for cluster state.
      *

server/src/test/java/org/opensearch/cluster/ClusterStateTests.java

@@ -57,6 +57,7 @@
 import org.opensearch.core.rest.RestStatus;
 import org.opensearch.core.xcontent.ToXContent;
 import org.opensearch.core.xcontent.XContentBuilder;
+import org.opensearch.indices.replication.common.ReplicationType;
 import org.opensearch.test.OpenSearchTestCase;
 import org.opensearch.test.TestCustomMetadata;
 
@@ -73,6 +74,7 @@
 import static java.util.Collections.emptyMap;
 import static java.util.Collections.emptySet;
 import static java.util.Collections.singletonMap;
+import static org.opensearch.cluster.ClusterName.CLUSTER_NAME_SETTING;
 import static org.opensearch.cluster.metadata.IndexMetadata.SETTING_VERSION_CREATED;
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.equalTo;
@@ -84,7 +86,7 @@ public void testSupersedes() {
         final DiscoveryNode node1 = new DiscoveryNode("node1", buildNewFakeTransportAddress(), emptyMap(), emptySet(), version);
         final DiscoveryNode node2 = new DiscoveryNode("node2", buildNewFakeTransportAddress(), emptyMap(), emptySet(), version);
         final DiscoveryNodes nodes = DiscoveryNodes.builder().add(node1).add(node2).build();
-        ClusterName name = ClusterName.CLUSTER_NAME_SETTING.getDefault(Settings.EMPTY);
+        ClusterName name = CLUSTER_NAME_SETTING.getDefault(Settings.EMPTY);
         ClusterState noClusterManager1 = ClusterState.builder(name).version(randomInt(5)).nodes(nodes).build();
         ClusterState noClusterManager2 = ClusterState.builder(name).version(randomInt(5)).nodes(nodes).build();
         ClusterState withClusterManager1a = ClusterState.builder(name)
@@ -115,6 +117,39 @@ public void testSupersedes() {
         );
     }
 
+    public void testIsSegmentReplicationEnabled() {
+        final String indexName = "test";
+        ClusterState clusterState = ClusterState.builder(CLUSTER_NAME_SETTING.getDefault(Settings.EMPTY)).build();
+        Settings.Builder builder = settings(Version.CURRENT).put(IndexMetadata.SETTING_REPLICATION_TYPE, ReplicationType.SEGMENT);
+        IndexMetadata.Builder indexMetadataBuilder = IndexMetadata.builder(indexName)
+            .settings(builder)
+            .numberOfShards(1)
+            .numberOfReplicas(1);
+        Metadata.Builder metadataBuilder = Metadata.builder().put(indexMetadataBuilder);
+        RoutingTable.Builder routingTableBuilder = RoutingTable.builder().addAsNew(indexMetadataBuilder.build());
+        clusterState = ClusterState.builder(clusterState)
+            .metadata(metadataBuilder.build())
+            .routingTable(routingTableBuilder.build())
+            .build();
+        assertTrue(clusterState.isSegmentReplicationEnabled(indexName));
+    }
+
+    public void testIsSegmentReplicationDisabled() {
+        final String indexName = "test";
+        ClusterState clusterState = ClusterState.builder(CLUSTER_NAME_SETTING.getDefault(Settings.EMPTY)).build();
+        IndexMetadata.Builder indexMetadataBuilder = IndexMetadata.builder(indexName)
+            .settings(settings(Version.CURRENT))
+            .numberOfShards(1)
+            .numberOfReplicas(1);
+        Metadata.Builder metadataBuilder = Metadata.builder().put(indexMetadataBuilder);
+        RoutingTable.Builder routingTableBuilder = RoutingTable.builder().addAsNew(indexMetadataBuilder.build());
+        clusterState = ClusterState.builder(clusterState)
+            .metadata(metadataBuilder.build())
+            .routingTable(routingTableBuilder.build())
+            .build();
+        assertFalse(clusterState.isSegmentReplicationEnabled(indexName));
+    }
+
     public void testBuilderRejectsNullCustom() {
         final ClusterState.Builder builder = ClusterState.builder(ClusterName.DEFAULT);
         final String key = randomAlphaOfLength(10);