[Remote Store] Add validator that forces segment replication type before enabling remote store (opensearch-project#4175)

* Add validator that forces segment replication type before enabling remote store

Signed-off-by: Sachin Kale <kalsac@amazon.com>

Author: sachinpkale

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

@@ -292,6 +292,32 @@ public Iterator<Setting<?>> settings() {
     public static final Setting<Boolean> INDEX_REMOTE_STORE_ENABLED_SETTING = Setting.boolSetting(
         SETTING_REMOTE_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 Object replicationType = settings.get(INDEX_REPLICATION_TYPE_SETTING);
+                if (replicationType != ReplicationType.SEGMENT && value == true) {
+                    throw new IllegalArgumentException(
+                        "Settings "
+                            + INDEX_REMOTE_STORE_ENABLED_SETTING.getKey()
+                            + " cannot be enabled when "
+                            + INDEX_REPLICATION_TYPE_SETTING.getKey()
+                            + " is set to "
+                            + settings.get(INDEX_REPLICATION_TYPE_SETTING)
+                    );
+                }
+            }
+
+            @Override
+            public Iterator<Setting<?>> settings() {
+                final List<Setting<?>> settings = Collections.singletonList(INDEX_REPLICATION_TYPE_SETTING);
+                return settings.iterator();
+            }
+        },
         Property.IndexScope,
         Property.Final
     );

server/src/test/java/org/opensearch/index/IndexSettingsTests.java

@@ -42,6 +42,7 @@
 import org.opensearch.common.unit.ByteSizeValue;
 import org.opensearch.common.unit.TimeValue;
 import org.opensearch.index.translog.Translog;
+import org.opensearch.indices.replication.common.ReplicationType;
 import org.opensearch.test.OpenSearchTestCase;
 import org.opensearch.test.VersionUtils;
 
@@ -854,4 +855,31 @@ public void testEnablingRemoteTranslogStoreFailsWhenRemoteSegmentDisabled() {
             iae.getMessage()
         );
     }
+
+    public void testEnablingRemoteStoreFailsWhenReplicationTypeIsDocument() {
+        Settings indexSettings = Settings.builder()
+            .put("index.replication.type", ReplicationType.DOCUMENT)
+            .put("index.remote_store.enabled", true)
+            .build();
+        IllegalArgumentException iae = expectThrows(
+            IllegalArgumentException.class,
+            () -> IndexMetadata.INDEX_REMOTE_STORE_ENABLED_SETTING.get(indexSettings)
+        );
+        assertEquals(
+            "Settings index.remote_store.enabled cannot be enabled when index.replication.type is set to DOCUMENT",
+            iae.getMessage()
+        );
+    }
+
+    public void testEnablingRemoteStoreFailsWhenReplicationTypeIsDefault() {
+        Settings indexSettings = Settings.builder().put("index.remote_store.enabled", true).build();
+        IllegalArgumentException iae = expectThrows(
+            IllegalArgumentException.class,
+            () -> IndexMetadata.INDEX_REMOTE_STORE_ENABLED_SETTING.get(indexSettings)
+        );
+        assertEquals(
+            "Settings index.remote_store.enabled cannot be enabled when index.replication.type is set to DOCUMENT",
+            iae.getMessage()
+        );
+    }
 }