[8.x] Add index and reindex request settings to speed up reindex (#119780)

docs/changelog/119780.yaml

@@ -0,0 +1,5 @@
+pr: 119780
+summary: Add index and reindex request settings to speed up reindex
+area: Data streams
+type: enhancement
+issues: []

x-pack/plugin/migrate/src/internalClusterTest/java/org/elasticsearch/xpack/migrate/action/ReindexDatastreamIndexTransportActionIT.java

@@ -15,6 +15,8 @@
 import org.elasticsearch.action.admin.indices.rollover.RolloverRequest;
 import org.elasticsearch.action.admin.indices.settings.get.GetSettingsRequest;
 import org.elasticsearch.action.admin.indices.settings.put.UpdateSettingsRequest;
+import org.elasticsearch.action.admin.indices.template.delete.DeleteIndexTemplateRequest;
+import org.elasticsearch.action.admin.indices.template.delete.TransportDeleteIndexTemplateAction;
 import org.elasticsearch.action.admin.indices.template.put.TransportPutComposableIndexTemplateAction;
 import org.elasticsearch.action.bulk.BulkRequest;
 import org.elasticsearch.action.bulk.BulkResponse;
@@ -155,7 +157,11 @@ public void testSettingsAddedBeforeReindex() throws Exception {
 
         // update with a dynamic setting
         var numReplicas = randomIntBetween(0, 10);
-        var dynamicSettings = Settings.builder().put(IndexMetadata.SETTING_NUMBER_OF_REPLICAS, numReplicas).build();
+        var refreshInterval = randomIntBetween(1, 100) + "s";
+        var dynamicSettings = Settings.builder()
+            .put(IndexMetadata.SETTING_NUMBER_OF_REPLICAS, numReplicas)
+            .put(IndexSettings.INDEX_REFRESH_INTERVAL_SETTING.getKey(), refreshInterval)
+            .build();
         indicesAdmin().updateSettings(new UpdateSettingsRequest(dynamicSettings, sourceIndex)).actionGet();
 
         // call reindex
@@ -167,6 +173,7 @@ public void testSettingsAddedBeforeReindex() throws Exception {
         var settingsResponse = indicesAdmin().getSettings(new GetSettingsRequest().indices(destIndex)).actionGet();
         assertEquals(numReplicas, Integer.parseInt(settingsResponse.getSetting(destIndex, IndexMetadata.SETTING_NUMBER_OF_REPLICAS)));
         assertEquals(numShards, Integer.parseInt(settingsResponse.getSetting(destIndex, IndexMetadata.SETTING_NUMBER_OF_SHARDS)));
+        assertEquals(refreshInterval, settingsResponse.getSetting(destIndex, IndexSettings.INDEX_REFRESH_INTERVAL_SETTING.getKey()));
     }
 
     public void testMappingsAddedToDestIndex() throws Exception {
@@ -229,6 +236,38 @@ public void testReadOnlyAddedBack() {
         removeReadOnly(destIndex);
     }
 
+    public void testUpdateSettingsDefaultsRestored() {
+        assumeTrue("requires the migration reindex feature flag", REINDEX_DATA_STREAM_FEATURE_FLAG.isEnabled());
+
+        // ESIntegTestCase creates a template random_index_template which contains a value for number_of_replicas.
+        // Since this test checks the behavior of default settings, there cannot be a value for number_of_replicas,
+        // so we delete the template within this method. This has no effect on other tests which will still
+        // have the template created during their setup.
+        assertAcked(
+            indicesAdmin().execute(TransportDeleteIndexTemplateAction.TYPE, new DeleteIndexTemplateRequest("random_index_template"))
+        );
+
+        var sourceIndex = randomAlphaOfLength(20).toLowerCase(Locale.ROOT);
+        assertAcked(indicesAdmin().create(new CreateIndexRequest(sourceIndex)));
+
+        // call reindex
+        var destIndex = client().execute(ReindexDataStreamIndexAction.INSTANCE, new ReindexDataStreamIndexAction.Request(sourceIndex))
+            .actionGet()
+            .getDestIndex();
+
+        var settingsResponse = indicesAdmin().getSettings(new GetSettingsRequest().indices(sourceIndex, destIndex)).actionGet();
+        var destSettings = settingsResponse.getIndexToSettings().get(destIndex);
+
+        assertEquals(
+            IndexMetadata.INDEX_NUMBER_OF_REPLICAS_SETTING.getDefault(destSettings),
+            IndexMetadata.INDEX_NUMBER_OF_REPLICAS_SETTING.get(destSettings)
+        );
+        assertEquals(
+            IndexSettings.INDEX_REFRESH_INTERVAL_SETTING.getDefault(destSettings),
+            IndexSettings.INDEX_REFRESH_INTERVAL_SETTING.get(destSettings)
+        );
+    }
+
     public void testSettingsAndMappingsFromTemplate() throws IOException {
         assumeTrue("requires the migration reindex feature flag", REINDEX_DATA_STREAM_FEATURE_FLAG.isEnabled());
 

x-pack/plugin/migrate/src/main/java/org/elasticsearch/xpack/migrate/action/ReindexDataStreamIndexTransportAction.java

@@ -14,6 +14,7 @@
 import org.elasticsearch.action.admin.indices.readonly.AddIndexBlockRequest;
 import org.elasticsearch.action.admin.indices.readonly.AddIndexBlockResponse;
 import org.elasticsearch.action.admin.indices.readonly.TransportAddIndexBlockAction;
+import org.elasticsearch.action.admin.indices.settings.put.UpdateSettingsRequest;
 import org.elasticsearch.action.support.ActionFilters;
 import org.elasticsearch.action.support.HandledTransportAction;
 import org.elasticsearch.action.support.IndicesOptions;
@@ -25,6 +26,7 @@
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.core.TimeValue;
+import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.index.reindex.BulkByScrollResponse;
 import org.elasticsearch.index.reindex.ReindexAction;
 import org.elasticsearch.index.reindex.ReindexRequest;
@@ -95,6 +97,7 @@ protected void doExecute(
             .<AcknowledgedResponse>andThen(l -> deleteDestIfExists(destIndexName, l, taskId))
             .<AcknowledgedResponse>andThen(l -> createIndex(sourceIndex, destIndexName, l, taskId))
             .<BulkByScrollResponse>andThen(l -> reindex(sourceIndexName, destIndexName, l, taskId))
+            .<AcknowledgedResponse>andThen(l -> copyOldSourceSettingsToDest(settingsBefore, destIndexName, l, taskId))
             .<AddIndexBlockResponse>andThen(l -> addBlockIfFromSource(WRITE, settingsBefore, destIndexName, l, taskId))
             .<AddIndexBlockResponse>andThen(l -> addBlockIfFromSource(READ_ONLY, settingsBefore, destIndexName, l, taskId))
             .andThenApply(ignored -> new ReindexDataStreamIndexAction.Response(destIndexName))
@@ -147,6 +150,8 @@ private void createIndex(
         var removeReadOnlyOverride = Settings.builder()
             .putNull(IndexMetadata.SETTING_READ_ONLY)
             .putNull(IndexMetadata.SETTING_BLOCKS_WRITE)
+            .put(IndexMetadata.SETTING_NUMBER_OF_REPLICAS, 0)
+            .put(IndexSettings.INDEX_REFRESH_INTERVAL_SETTING.getKey(), -1)
             .build();
 
         var request = new CreateIndexFromSourceAction.Request(
@@ -168,6 +173,7 @@ private void reindex(String sourceIndexName, String destIndexName, ActionListene
         reindexRequest.getSearchRequest().source().fetchSource(true);
         reindexRequest.setDestIndex(destIndexName);
         reindexRequest.setParentTask(parentTaskId);
+        reindexRequest.setSlices(0); // equivalent to slices=auto in rest api
         client.execute(ReindexAction.INSTANCE, reindexRequest, listener);
     }
 
@@ -186,6 +192,35 @@ private void addBlockIfFromSource(
         }
     }
 
+    private void copyOldSourceSettingsToDest(
+        Settings settingsBefore,
+        String destIndexName,
+        ActionListener<AcknowledgedResponse> listener,
+        TaskId parentTaskId
+    ) {
+        logger.debug("Updating settings on destination index after reindex completes");
+
+        var settings = Settings.builder();
+        copySettingOrUnset(settingsBefore, settings, IndexMetadata.SETTING_NUMBER_OF_REPLICAS);
+        copySettingOrUnset(settingsBefore, settings, IndexSettings.INDEX_REFRESH_INTERVAL_SETTING.getKey());
+
+        var updateSettingsRequest = new UpdateSettingsRequest(settings.build(), destIndexName);
+        updateSettingsRequest.setParentTask(parentTaskId);
+        var errorMessage = String.format(Locale.ROOT, "Could not update settings on index [%s]", destIndexName);
+        client.admin().indices().updateSettings(updateSettingsRequest, failIfNotAcknowledged(listener, errorMessage));
+    }
+
+    private static void copySettingOrUnset(Settings settingsBefore, Settings.Builder builder, String setting) {
+        // if setting was explicitly added to the source index
+        if (settingsBefore.get(setting) != null) {
+            // copy it back to the dest index
+            builder.copy(setting, settingsBefore);
+        } else {
+            // otherwise, delete from dest index so that it loads from the settings default
+            builder.putNull(setting);
+        }
+    }
+
     public static String generateDestIndexName(String sourceIndex) {
         return "migrated-" + sourceIndex;
     }