Move segment replication setting to IndexMetadata so that it can be set during index creation.

server/src/internalClusterTest/java/org/opensearch/indices/replication/SegmentReplicationIT.java

@@ -0,0 +1,59 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.indices.replication;
+
+import org.opensearch.cluster.metadata.IndexMetadata;
+import org.opensearch.common.settings.Settings;
+import org.opensearch.test.BackgroundIndexer;
+import org.opensearch.test.OpenSearchIntegTestCase;
+import org.opensearch.test.OpenSearchIntegTestCase.ClusterScope;
+
+import static org.opensearch.test.hamcrest.OpenSearchAssertions.assertHitCount;
+
+@ClusterScope(scope = OpenSearchIntegTestCase.Scope.TEST, numDataNodes = 0)
+public class SegmentReplicationIT extends OpenSearchIntegTestCase {
+
+    private static final String INDEX_NAME = "test-idx-1";
+    private static final int SHARD_COUNT = 1;
+    private static final int REPLICA_COUNT = 1;
+
+    public void testReplicationAfterPrimaryRefreshAndFlush() throws Exception {
+        final String nodeA = internalCluster().startNode();
+        final String nodeB = internalCluster().startNode();
+        createIndex(
+            INDEX_NAME,
+            Settings.builder()
+                .put(IndexMetadata.SETTING_NUMBER_OF_SHARDS, SHARD_COUNT)
+                .put(IndexMetadata.SETTING_NUMBER_OF_REPLICAS, REPLICA_COUNT)
+                .put(IndexMetadata.SETTING_SEGMENT_REPLICATION, true)
+                .build()
+        );
+        ensureGreen(INDEX_NAME);
+
+        final int initialDocCount = scaledRandomIntBetween(0, 200);
+        try (BackgroundIndexer indexer = new BackgroundIndexer(INDEX_NAME, "_doc", client(), initialDocCount)) {
+            waitForDocs(initialDocCount, indexer);
+        }
+        refresh(INDEX_NAME);
+        // wait a short amount of time to give replication a chance to complete.
+        Thread.sleep(1000);
+        assertHitCount(client(nodeA).prepareSearch(INDEX_NAME).setSize(0).setPreference("_only_local").get(), initialDocCount);
+        assertHitCount(client(nodeB).prepareSearch(INDEX_NAME).setSize(0).setPreference("_only_local").get(), initialDocCount);
+
+        final int additionalDocCount = scaledRandomIntBetween(0, 200);
+        final int totalDocs = initialDocCount + additionalDocCount;
+        try (BackgroundIndexer indexer = new BackgroundIndexer(INDEX_NAME, "_doc", client(), additionalDocCount)) {
+            waitForDocs(additionalDocCount, indexer);
+        }
+        flush(INDEX_NAME);
+        Thread.sleep(1000);
+        assertHitCount(client(nodeA).prepareSearch(INDEX_NAME).setSize(0).setPreference("_only_local").get(), totalDocs);
+        assertHitCount(client(nodeB).prepareSearch(INDEX_NAME).setSize(0).setPreference("_only_local").get(), totalDocs);
+    }
+}

server/src/main/java/org/opensearch/cluster/metadata/IndexMetadata.java

@@ -259,6 +259,17 @@ public Iterator<Setting<?>> settings() {
         Property.IndexScope
     );
 
+    public static final String SETTING_SEGMENT_REPLICATION = "index.replication.segment_replication";
+    /**
+     * Used to specify if the index should use segment replication. If false, document replication is used.
+     */
+    public static final Setting<Boolean> INDEX_SEGMENT_REPLICATION_SETTING = Setting.boolSetting(
+        SETTING_SEGMENT_REPLICATION,
+        false,
+        Property.IndexScope,
+        Property.Final
+    );
+
     public static final String SETTING_AUTO_EXPAND_REPLICAS = "index.auto_expand_replicas";
     public static final Setting<AutoExpandReplicas> INDEX_AUTO_EXPAND_REPLICAS_SETTING = AutoExpandReplicas.SETTING;
 

server/src/main/java/org/opensearch/common/settings/IndexScopedSettings.java

@@ -97,6 +97,7 @@ public final class IndexScopedSettings extends AbstractScopedSettings {
                 IndexMetadata.INDEX_DATA_PATH_SETTING,
                 IndexMetadata.INDEX_FORMAT_SETTING,
                 IndexMetadata.INDEX_HIDDEN_SETTING,
+                IndexMetadata.INDEX_SEGMENT_REPLICATION_SETTING,
                 SearchSlowLog.INDEX_SEARCH_SLOWLOG_THRESHOLD_FETCH_DEBUG_SETTING,
                 SearchSlowLog.INDEX_SEARCH_SLOWLOG_THRESHOLD_FETCH_WARN_SETTING,
                 SearchSlowLog.INDEX_SEARCH_SLOWLOG_THRESHOLD_FETCH_INFO_SETTING,
@@ -187,7 +188,6 @@ public final class IndexScopedSettings extends AbstractScopedSettings {
                 IndexSettings.FINAL_PIPELINE,
                 MetadataIndexStateService.VERIFIED_BEFORE_CLOSE_SETTING,
                 ExistingShardsAllocator.EXISTING_SHARDS_ALLOCATOR_SETTING,
-                IndexSettings.INDEX_SEGMENT_REPLICATION_SETTING,
 
                 // validate that built-in similarities don't get redefined
                 Setting.groupSetting("index.similarity.", (s) -> {

server/src/main/java/org/opensearch/index/IndexSettings.java

@@ -503,22 +503,13 @@ public final class IndexSettings {
         Setting.Property.IndexScope
     );
 
-    /**
-     * Used to specify if the index should use segment replication. If false, document replication is used.
-     */
-    public static final Setting<Boolean> INDEX_SEGMENT_REPLICATION_SETTING = Setting.boolSetting(
-        "index.replication.segment_replication",
-        false,
-        Property.IndexScope,
-        Property.Final
-    );
-
     private final Index index;
     private final Version version;
     private final Logger logger;
     private final String nodeName;
     private final Settings nodeSettings;
     private final int numberOfShards;
+    private final Boolean isSegrepEnabled;
     // volatile fields are updated via #updateIndexMetadata(IndexMetadata) under lock
     private volatile Settings settings;
     private volatile IndexMetadata indexMetadata;
@@ -661,7 +652,7 @@ public IndexSettings(final IndexMetadata indexMetadata, final Settings nodeSetti
         nodeName = Node.NODE_NAME_SETTING.get(settings);
         this.indexMetadata = indexMetadata;
         numberOfShards = settings.getAsInt(IndexMetadata.SETTING_NUMBER_OF_SHARDS, null);
-
+        isSegrepEnabled = settings.getAsBoolean(IndexMetadata.SETTING_SEGMENT_REPLICATION, false);
         this.searchThrottled = INDEX_SEARCH_THROTTLED.get(settings);
         this.queryStringLenient = QUERY_STRING_LENIENT_SETTING.get(settings);
         this.queryStringAnalyzeWildcard = QUERY_STRING_ANALYZE_WILDCARD.get(nodeSettings);
@@ -891,6 +882,10 @@ public int getNumberOfReplicas() {
         return settings.getAsInt(IndexMetadata.SETTING_NUMBER_OF_REPLICAS, null);
     }
 
+    public boolean isSegrepEnabled() {
+        return isSegrepEnabled;
+    }
+
     /**
      * Returns the node settings. The settings returned from {@link #getSettings()} are a merged version of the
      * index settings and the node settings where node settings are overwritten by index settings.

server/src/main/java/org/opensearch/index/shard/IndexShard.java

@@ -845,7 +845,7 @@ public Engine.IndexResult applyIndexOperationOnReplica(
         boolean isRetry,
         SourceToParse sourceToParse
     ) throws IOException {
-        Boolean isSegRepEnabled = indexSettings.getValue(IndexSettings.INDEX_SEGMENT_REPLICATION_SETTING);
+        Boolean isSegRepEnabled = indexSettings.isSegrepEnabled();
         if (isSegRepEnabled != null && isSegRepEnabled) {
             Engine.Index index;
             try {