[Backport Main] Add UnmodifiableOnRestore property to index.knn setting

CHANGELOG.md

@@ -22,6 +22,18 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 ### Features
 ### Enhancements
 ### Bug Fixes
+* Fixing the bug when a segment has no vector field present for disk based vector search (#2282)[https://github.com/opensearch-project/k-NN/pull/2282]
+* Fixing the bug where search fails with "fields" parameter for an index with a knn_vector field (#2314)[https://github.com/opensearch-project/k-NN/pull/2314]
+* Fix for NPE while merging segments after all the vector fields docs are deleted (#2365)[https://github.com/opensearch-project/k-NN/pull/2365]
+* Allow validation for non knn index only after 2.17.0 (#2315)[https://github.com/opensearch-project/k-NN/pull/2315]
+* Fixing the bug to prevent updating the index.knn setting after index creation(#2348)[https://github.com/opensearch-project/k-NN/pull/2348]
+* Release query vector memory after execution (#2346)[https://github.com/opensearch-project/k-NN/pull/2346]
+* Fix shard level rescoring disabled setting flag (#2352)[https://github.com/opensearch-project/k-NN/pull/2352]
+* Fix filter rewrite logic which was resulting in getting inconsistent / incorrect results for cases where filter was getting rewritten for shards (#2359)[https://github.com/opensearch-project/k-NN/pull/2359]
+* Fixing it to retrieve space_type from index setting when both method and top level don't have the value. [#2374](https://github.com/opensearch-project/k-NN/pull/2374)
+* Fixing the bug where setting rescore as false for on_disk knn_vector query is a no-op (#2399)[https://github.com/opensearch-project/k-NN/pull/2399]
+* Fixing bug where mapping accepts both dimension and model-id (#2410)[https://github.com/opensearch-project/k-NN/pull/2410]
+* Fixing the bug to prevent index.knn setting from being modified or removed on restore snapshot (#2445)[https://github.com/opensearch-project/k-NN/pull/2445]
 * Fix derived source for binary and byte vectors [#2533](https://github.com/opensearch-project/k-NN/pull/2533/)
 * Fix the put mapping issue for already created index with flat mapper [#2542](https://github.com/opensearch-project/k-NN/pull/2542)
 ### Infrastructure

src/main/java/org/opensearch/knn/index/KNNSettings.java

@@ -283,7 +283,13 @@ public class KNNSettings {
     /**
      * This setting identifies KNN index.
      */
-    public static final Setting<Boolean> IS_KNN_INDEX_SETTING = Setting.boolSetting(KNN_INDEX, false, IndexScope, Final);
+    public static final Setting<Boolean> IS_KNN_INDEX_SETTING = Setting.boolSetting(
+        KNN_INDEX,
+        false,
+        IndexScope,
+        Final,
+        UnmodifiableOnRestore
+    );
 
     /**
      * index_thread_quantity - the parameter specifies how many threads the nms library should use to create the graph.

src/test/java/org/opensearch/knn/index/RestoreSnapshotIT.java

@@ -0,0 +1,108 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.opensearch.knn.index;
+
+import org.opensearch.client.Request;
+import org.opensearch.client.Response;
+import org.opensearch.client.ResponseException;
+import org.opensearch.common.xcontent.json.JsonXContent;
+import org.opensearch.core.xcontent.XContentBuilder;
+import org.opensearch.knn.KNNRestTestCase;
+import org.junit.Before;
+import org.junit.Test;
+import lombok.SneakyThrows;
+import static org.hamcrest.Matchers.containsString;
+
+public class RestoreSnapshotIT extends KNNRestTestCase {
+
+    private String index = "test-index";;
+    private String snapshot = "snapshot-" + index;
+    private String repository = "repo";
+
+    @Before
+    @SneakyThrows
+    public void setUp() {
+        super.setUp();
+        setupSnapshotRestore(index, snapshot, repository);
+    }
+
+    @Test
+    @SneakyThrows
+    public void testKnnSettingIsModifiable_whenRestore_thenSuccess() {
+        // valid restore
+        XContentBuilder restoreCommand = JsonXContent.contentBuilder().startObject();
+        restoreCommand.field("indices", index);
+        restoreCommand.field("rename_pattern", index);
+        restoreCommand.field("rename_replacement", "restored-" + index);
+        restoreCommand.startObject("index_settings");
+        {
+            restoreCommand.field("knn.model.index.number_of_shards", 1);
+        }
+        restoreCommand.endObject();
+        restoreCommand.endObject();
+        Request restoreRequest = new Request("POST", "/_snapshot/" + repository + "/" + snapshot + "/_restore");
+        restoreRequest.addParameter("wait_for_completion", "true");
+        restoreRequest.setJsonEntity(restoreCommand.toString());
+
+        final Response restoreResponse = client().performRequest(restoreRequest);
+        assertEquals(200, restoreResponse.getStatusLine().getStatusCode());
+    }
+
+    @Test
+    @SneakyThrows
+    public void testKnnSettingIsUnmodifiable_whenRestore_thenFailure() {
+        // invalid restore
+        XContentBuilder restoreCommand = JsonXContent.contentBuilder().startObject();
+        restoreCommand.field("indices", index);
+        restoreCommand.field("rename_pattern", index);
+        restoreCommand.field("rename_replacement", "restored-" + index);
+        restoreCommand.startObject("index_settings");
+        {
+            restoreCommand.field("index.knn", false);
+        }
+        restoreCommand.endObject();
+        restoreCommand.endObject();
+        Request restoreRequest = new Request("POST", "/_snapshot/" + repository + "/" + snapshot + "/_restore");
+        restoreRequest.addParameter("wait_for_completion", "true");
+        restoreRequest.setJsonEntity(restoreCommand.toString());
+        final ResponseException error = expectThrows(ResponseException.class, () -> client().performRequest(restoreRequest));
+        assertThat(error.getMessage(), containsString("cannot modify UnmodifiableOnRestore setting [index.knn]" + " on restore"));
+    }
+
+    @Test
+    @SneakyThrows
+    public void testKnnSettingCanBeIgnored_whenRestore_thenSuccess() {
+        // valid restore
+        XContentBuilder restoreCommand = JsonXContent.contentBuilder().startObject();
+        restoreCommand.field("indices", index);
+        restoreCommand.field("rename_pattern", index);
+        restoreCommand.field("rename_replacement", "restored-" + index);
+        restoreCommand.field("ignore_index_settings", "knn.model.index.number_of_shards");
+        restoreCommand.endObject();
+        Request restoreRequest = new Request("POST", "/_snapshot/" + repository + "/" + snapshot + "/_restore");
+        restoreRequest.addParameter("wait_for_completion", "true");
+        restoreRequest.setJsonEntity(restoreCommand.toString());
+        final Response restoreResponse = client().performRequest(restoreRequest);
+        assertEquals(200, restoreResponse.getStatusLine().getStatusCode());
+    }
+
+    @Test
+    @SneakyThrows
+    public void testKnnSettingCannotBeIgnored_whenRestore_thenFailure() {
+        // invalid restore
+        XContentBuilder restoreCommand = JsonXContent.contentBuilder().startObject();
+        restoreCommand.field("indices", index);
+        restoreCommand.field("rename_pattern", index);
+        restoreCommand.field("rename_replacement", "restored-" + index);
+        restoreCommand.field("ignore_index_settings", "index.knn");
+        restoreCommand.endObject();
+        Request restoreRequest = new Request("POST", "/_snapshot/" + repository + "/" + snapshot + "/_restore");
+        restoreRequest.addParameter("wait_for_completion", "true");
+        restoreRequest.setJsonEntity(restoreCommand.toString());
+        final ResponseException error = expectThrows(ResponseException.class, () -> client().performRequest(restoreRequest));
+        assertThat(error.getMessage(), containsString("cannot remove UnmodifiableOnRestore setting [index.knn] on restore"));
+    }
+}

src/testFixtures/java/org/opensearch/knn/KNNRestTestCase.java

@@ -19,6 +19,7 @@
 import org.junit.AfterClass;
 import org.junit.Before;
 import org.opensearch.Version;
+import org.opensearch.common.xcontent.support.XContentMapValues;
 import org.opensearch.client.Request;
 import org.opensearch.client.Response;
 import org.opensearch.common.settings.Settings;
@@ -86,6 +87,8 @@
 import static org.opensearch.knn.TestUtils.VECTOR_TYPE;
 import static org.opensearch.knn.TestUtils.computeGroundTruthValues;
 import static org.opensearch.knn.common.KNNConstants.CLEAR_CACHE;
+import static org.hamcrest.Matchers.hasSize;
+import static org.hamcrest.Matchers.notNullValue;
 import static org.opensearch.knn.common.KNNConstants.DIMENSION;
 import static org.opensearch.knn.common.KNNConstants.ENCODER_PARAMETER_PQ_CODE_SIZE;
 import static org.opensearch.knn.common.KNNConstants.ENCODER_PARAMETER_PQ_M;
@@ -2370,4 +2373,29 @@ protected boolean isRemoteIndexBuildSupported(final Optional<String> bwcVersion)
     protected static String randomLowerCaseString() {
         return randomAlphaOfLengthBetween(MIN_CODE_UNITS, MAX_CODE_UNITS).toLowerCase(Locale.ROOT);
     }
+
+    @SneakyThrows
+    protected void setupSnapshotRestore(String index, String snapshot, String repository) {
+        Request clusterSettingsRequest = new Request("GET", "/_cluster/settings");
+        clusterSettingsRequest.addParameter("include_defaults", "true");
+        Response clusterSettingsResponse = client().performRequest(clusterSettingsRequest);
+        Map<String, Object> clusterSettings = entityAsMap(clusterSettingsResponse);
+
+        @SuppressWarnings("unchecked")
+        List<String> pathRepos = (List<String>) XContentMapValues.extractValue("defaults.path.repo", clusterSettings);
+        assertThat(pathRepos, notNullValue());
+        assertThat(pathRepos, hasSize(1));
+
+        final String pathRepo = pathRepos.get(0);
+
+        // create index
+        createIndex(index, getDefaultIndexSettings());
+
+        // create repo
+        Settings repoSettings = Settings.builder().put("compress", randomBoolean()).put("location", pathRepo).build();
+        registerRepository(repository, "fs", true, repoSettings);
+
+        // create snapshot
+        createSnapshot(repository, snapshot, true);
+    }
 }