Introduce Remote translog feature flag

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

@@ -284,6 +284,8 @@ public Iterator<Setting<?>> settings() {
     );
 
     public static final String SETTING_REMOTE_STORE_ENABLED = "index.remote_store.enabled";
+
+    public static final String SETTING_REMOTE_TRANSLOG_STORE_ENABLED = "index.remote_store.translog.enabled";
     /**
      * Used to specify if the index data should be persisted in the remote store.
      */
@@ -294,6 +296,42 @@ public Iterator<Setting<?>> settings() {
         Property.Final
     );
 
+    /**
+     * Used to specify if the index translog operations should be persisted in the remote store.
+     */
+    public static final Setting<Boolean> INDEX_REMOTE_TRANSLOG_STORE_ENABLED_SETTING = Setting.boolSetting(
+        SETTING_REMOTE_TRANSLOG_STORE_ENABLED,
+        false,
+        new Setting.Validator<>() {
+
+            @Override
+            public void validate(final Boolean value) {}
+
+            @Override
+            public void validate(final Boolean value, final Map<Setting<?>, Object> settings) {
+                final Boolean isRemoteSegmentStoreEnabled = (Boolean) settings.get(INDEX_REMOTE_STORE_ENABLED_SETTING);
+                if (isRemoteSegmentStoreEnabled == false && value == true) {
+                    throw new IllegalArgumentException(
+                        "Settings "
+                            + INDEX_REMOTE_TRANSLOG_STORE_ENABLED_SETTING.getKey()
+                            + " cannot be enabled when "
+                            + INDEX_REMOTE_STORE_ENABLED_SETTING.getKey()
+                            + " is set to "
+                            + settings.get(INDEX_REMOTE_STORE_ENABLED_SETTING)
+                    );
+                }
+            }
+
+            @Override
+            public Iterator<Setting<?>> settings() {
+                final List<Setting<?>> settings = Collections.singletonList(INDEX_REMOTE_STORE_ENABLED_SETTING);
+                return settings.iterator();
+            }
+        },
+        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

@@ -61,6 +61,7 @@
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashSet;
+import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import java.util.function.Predicate;
@@ -218,11 +219,11 @@ public final class IndexScopedSettings extends AbstractScopedSettings {
      * is ready for production release, the feature flag can be removed, and the
      * setting should be moved to {@link #BUILT_IN_INDEX_SETTINGS}.
      */
-    public static final Map<String, Setting> FEATURE_FLAGGED_INDEX_SETTINGS = Map.of(
+    public static final Map<String, List<Setting>> FEATURE_FLAGGED_INDEX_SETTINGS = Map.of(
         FeatureFlags.REPLICATION_TYPE,
-        IndexMetadata.INDEX_REPLICATION_TYPE_SETTING,
+        Collections.singletonList(IndexMetadata.INDEX_REPLICATION_TYPE_SETTING),
         FeatureFlags.REMOTE_STORE,
-        IndexMetadata.INDEX_REMOTE_STORE_ENABLED_SETTING
+        Arrays.asList(IndexMetadata.INDEX_REMOTE_STORE_ENABLED_SETTING, IndexMetadata.INDEX_REMOTE_TRANSLOG_STORE_ENABLED_SETTING)
     );
 
     public static final IndexScopedSettings DEFAULT_SCOPED_SETTINGS = new IndexScopedSettings(Settings.EMPTY, BUILT_IN_INDEX_SETTINGS);

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

@@ -88,9 +88,9 @@ public SettingsModule(
             registerSetting(setting);
         }
 
-        for (Map.Entry<String, Setting> featureFlaggedSetting : IndexScopedSettings.FEATURE_FLAGGED_INDEX_SETTINGS.entrySet()) {
+        for (Map.Entry<String, List<Setting>> featureFlaggedSetting : IndexScopedSettings.FEATURE_FLAGGED_INDEX_SETTINGS.entrySet()) {
             if (FeatureFlags.isEnabled(featureFlaggedSetting.getKey())) {
-                registerSetting(featureFlaggedSetting.getValue());
+                featureFlaggedSetting.getValue().forEach(feature -> registerSetting(feature));
             }
         }
 

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

@@ -559,6 +559,7 @@ public final class IndexSettings {
     private final int numberOfShards;
     private final ReplicationType replicationType;
     private final boolean isRemoteStoreEnabled;
+    private final boolean isRemoteTranslogStoreEnabled;
     // volatile fields are updated via #updateIndexMetadata(IndexMetadata) under lock
     private volatile Settings settings;
     private volatile IndexMetadata indexMetadata;
@@ -719,7 +720,7 @@ public IndexSettings(final IndexMetadata indexMetadata, final Settings nodeSetti
         numberOfShards = settings.getAsInt(IndexMetadata.SETTING_NUMBER_OF_SHARDS, null);
         replicationType = ReplicationType.parseString(settings.get(IndexMetadata.SETTING_REPLICATION_TYPE));
         isRemoteStoreEnabled = settings.getAsBoolean(IndexMetadata.SETTING_REMOTE_STORE_ENABLED, false);
-
+        isRemoteTranslogStoreEnabled = settings.getAsBoolean(IndexMetadata.SETTING_REMOTE_TRANSLOG_STORE_ENABLED, false);
         this.searchThrottled = INDEX_SEARCH_THROTTLED.get(settings);
         this.queryStringLenient = QUERY_STRING_LENIENT_SETTING.get(settings);
         this.queryStringAnalyzeWildcard = QUERY_STRING_ANALYZE_WILDCARD.get(nodeSettings);
@@ -971,6 +972,13 @@ public boolean isRemoteStoreEnabled() {
         return isRemoteStoreEnabled;
     }
 
+    /**
+     * Returns if remote translog store is enabled for this index.
+     */
+    public boolean isRemoteTranslogStoreEnabled() {
+        return isRemoteTranslogStoreEnabled;
+    }
+
     /**
      * 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/test/java/org/opensearch/index/IndexSettingsTests.java

@@ -41,7 +41,6 @@
 import org.opensearch.common.settings.Settings;
 import org.opensearch.common.unit.ByteSizeValue;
 import org.opensearch.common.unit.TimeValue;
-import org.opensearch.common.util.FeatureFlags;
 import org.opensearch.index.translog.Translog;
 import org.opensearch.test.OpenSearchTestCase;
 import org.opensearch.test.VersionUtils;
@@ -57,7 +56,6 @@
 import static org.hamcrest.CoreMatchers.equalTo;
 import static org.hamcrest.core.StringContains.containsString;
 import static org.hamcrest.object.HasToString.hasToString;
-import static org.opensearch.common.settings.IndexScopedSettings.FEATURE_FLAGGED_INDEX_SETTINGS;
 
 public class IndexSettingsTests extends OpenSearchTestCase {
 
@@ -777,9 +775,42 @@ public void testRemoteStoreExplicitSetting() {
         assertTrue(settings.isRemoteStoreEnabled());
     }
 
+    public void testRemoteTranslogStoreDefaultSetting() {
+        IndexMetadata metadata = newIndexMeta(
+            "index",
+            Settings.builder().put(IndexMetadata.SETTING_VERSION_CREATED, Version.CURRENT).build()
+        );
+        IndexSettings settings = new IndexSettings(metadata, Settings.EMPTY);
+        assertFalse(settings.isRemoteTranslogStoreEnabled());
+    }
+
+    public void testRemoteTranslogStoreExplicitSetting() {
+        IndexMetadata metadata = newIndexMeta(
+            "index",
+            Settings.builder()
+                .put(IndexMetadata.SETTING_VERSION_CREATED, Version.CURRENT)
+                .put(IndexMetadata.SETTING_REMOTE_TRANSLOG_STORE_ENABLED, true)
+                .build()
+        );
+        IndexSettings settings = new IndexSettings(metadata, Settings.EMPTY);
+        assertTrue(settings.isRemoteTranslogStoreEnabled());
+    }
+
+    public void testRemoteTranslogStoreNullSetting() {
+        Settings indexSettings = Settings.builder()
+            .put("index.remote_store.translog.enabled", "null")
+            .put("index.remote_store.enabled", randomBoolean())
+            .build();
+        IllegalArgumentException iae = expectThrows(
+            IllegalArgumentException.class,
+            () -> IndexMetadata.INDEX_REMOTE_TRANSLOG_STORE_ENABLED_SETTING.get(indexSettings)
+        );
+        assertEquals("Failed to parse value [null] as only [true] or [false] are allowed.", iae.getMessage());
+    }
+
     public void testUpdateRemoteStoreFails() {
         Set<Setting<?>> remoteStoreSettingSet = new HashSet<>();
-        remoteStoreSettingSet.add(FEATURE_FLAGGED_INDEX_SETTINGS.get(FeatureFlags.REMOTE_STORE));
+        remoteStoreSettingSet.add(IndexMetadata.INDEX_REMOTE_STORE_ENABLED_SETTING);
         IndexScopedSettings settings = new IndexScopedSettings(Settings.EMPTY, remoteStoreSettingSet);
         IllegalArgumentException error = expectThrows(
             IllegalArgumentException.class,
@@ -792,4 +823,35 @@ public void testUpdateRemoteStoreFails() {
         );
         assertEquals(error.getMessage(), "final index setting [index.remote_store.enabled], not updateable");
     }
+
+    public void testUpdateRemoteTranslogStoreFails() {
+        Set<Setting<?>> remoteStoreSettingSet = new HashSet<>();
+        remoteStoreSettingSet.add(IndexMetadata.INDEX_REMOTE_TRANSLOG_STORE_ENABLED_SETTING);
+        IndexScopedSettings settings = new IndexScopedSettings(Settings.EMPTY, remoteStoreSettingSet);
+        IllegalArgumentException error = expectThrows(
+            IllegalArgumentException.class,
+            () -> settings.updateSettings(
+                Settings.builder().put("index.remote_store.translog.enabled", randomBoolean()).build(),
+                Settings.builder(),
+                Settings.builder(),
+                "index"
+            )
+        );
+        assertEquals(error.getMessage(), "final index setting [index.remote_store.translog.enabled], not updateable");
+    }
+
+    public void testEnablingRemoteTranslogStoreFailsWhenRemoteSegmentDisabled() {
+        Settings indexSettings = Settings.builder()
+            .put("index.remote_store.translog.enabled", true)
+            .put("index.remote_store.enabled", false)
+            .build();
+        IllegalArgumentException iae = expectThrows(
+            IllegalArgumentException.class,
+            () -> IndexMetadata.INDEX_REMOTE_TRANSLOG_STORE_ENABLED_SETTING.get(indexSettings)
+        );
+        assertEquals(
+            "Settings index.remote_store.translog.enabled cannot be enabled when index.remote_store.enabled is set to false",
+            iae.getMessage()
+        );
+    }
 }