com.amazonaws.athena.connector.lambda.handlers.GlueMetadataHandler Maven / Gradle / Ivy
package com.amazonaws.athena.connector.lambda.handlers;
/*-
* #%L
* Amazon Athena Query Federation SDK
* %%
* Copyright (C) 2019 Amazon Web Services
* %%
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
* #L%
*/
import com.amazonaws.ClientConfiguration;
import com.amazonaws.athena.connector.lambda.data.BlockAllocator;
import com.amazonaws.athena.connector.lambda.data.SchemaBuilder;
import com.amazonaws.athena.connector.lambda.domain.TableName;
import com.amazonaws.athena.connector.lambda.metadata.GetTableRequest;
import com.amazonaws.athena.connector.lambda.metadata.GetTableResponse;
import com.amazonaws.athena.connector.lambda.metadata.ListSchemasRequest;
import com.amazonaws.athena.connector.lambda.metadata.ListSchemasResponse;
import com.amazonaws.athena.connector.lambda.metadata.ListTablesRequest;
import com.amazonaws.athena.connector.lambda.metadata.ListTablesResponse;
import com.amazonaws.athena.connector.lambda.metadata.MetadataRequest;
import com.amazonaws.athena.connector.lambda.metadata.glue.GlueFieldLexer;
import com.amazonaws.athena.connector.lambda.security.EncryptionKeyFactory;
import com.amazonaws.services.athena.AmazonAthena;
import com.amazonaws.services.glue.AWSGlue;
import com.amazonaws.services.glue.AWSGlueClientBuilder;
import com.amazonaws.services.glue.model.Column;
import com.amazonaws.services.glue.model.Database;
import com.amazonaws.services.glue.model.GetDatabasesRequest;
import com.amazonaws.services.glue.model.GetDatabasesResult;
import com.amazonaws.services.glue.model.GetTableResult;
import com.amazonaws.services.glue.model.GetTablesRequest;
import com.amazonaws.services.glue.model.GetTablesResult;
import com.amazonaws.services.glue.model.Table;
import com.amazonaws.services.secretsmanager.AWSSecretsManager;
import com.google.common.base.Splitter;
import com.google.common.base.Strings;
import com.google.common.collect.ImmutableMap;
import org.apache.arrow.util.VisibleForTesting;
import org.apache.arrow.vector.types.pojo.ArrowType;
import org.apache.arrow.vector.types.pojo.Field;
import org.apache.arrow.vector.types.pojo.Schema;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import static com.amazonaws.athena.connector.lambda.metadata.ListTablesRequest.UNLIMITED_PAGE_SIZE_VALUE;
/**
* This class allows you to leverage AWS Glue's DataCatalog to satisfy portions of the functionality required in a
* MetadataHandler. More precisely, this implementation uses AWS Glue's DataCatalog to implement:
*
* - doListSchemas(...)
*
- doListTables(...)
*
- doGetTable(...)
*
* When you extend this class you can optionally provide a DatabaseFilter and/or TableFilter to decide which Databases
* (aka schemas) and Tables are eligible for use with your connector. You can find examples of this in the
* athena-hbase and athena-docdb connector modules. A common reason for this is when you happen to have databases/tables
* in Glue which match the names of databases and tables in your source but that aren't actually relevant. In such cases
* you may choose to ignore those Glue tables.
*
* At present this class does not retrieve partition information from AWS Glue's DataCatalog. There is an open task
* for how best to handle partitioning information in this class: https://github.com/awslabs/aws-athena-query-federation/issues/5
* It is unclear at this time how many sources will have meaningful partition info in Glue but many sources (DocDB, Hbase, Redis)
* benefited from having basic schema information in Glue. As a result we punted support for partition information to
* a later time.
*
* @note All schema names, table names, and column names must be lower case at this time. Any entities that are uppercase or
* mixed case will not be accessible in queries and will be lower cased by Athena's engine to ensure consistency across
* sources. As such you may need to handle this when integrating with a source that supports mixed case. As an example,
* you can look at the CloudwatchTableResolver in the athena-cloudwatch module for one potential approach to this challenge.
* @see MetadataHandler
*/
public abstract class GlueMetadataHandler
extends MetadataHandler
{
private static final Logger logger = LoggerFactory.getLogger(GlueMetadataHandler.class);
/**
* The maximum number of tables returned in a single response (as defined in the Glue API docs).
*/
protected static final int GET_TABLES_REQUEST_MAX_RESULTS = 100;
// configOption to control whether or not glue is disabled
private static final String DISABLE_GLUE = "disable_glue";
//name of the environment variable that can be used to set which Glue catalog to use (e.g. setting this to
//a different aws account id allows you to use cross-account catalogs)
private static final String CATALOG_NAME_ENV_OVERRIDE = "glue_catalog";
//This is to override the connection timeout on the Glue client.
//The default is 10 seconds, which when retried is 40 seconds.
//Lower to 250 ms, 1 second with retry.
private static final int CONNECT_TIMEOUT = 250;
//Splitter for inline map properties
private static final Splitter.MapSplitter MAP_SPLITTER = Splitter.on(",").trimResults().withKeyValueSeparator("=");
//Regex we expect for a table resource ARN
private static final Pattern TABLE_ARN_REGEX = Pattern.compile("^arn:(?:aws|aws-cn|aws-us-gov):[a-z]+:[a-z1-9-]+:[0-9]{12}:table\\/(.+)$");
//Regex we expect for a lambda function ARN
private static final String FUNCTION_ARN_REGEX = "arn:aws[a-zA-Z-]*?:lambda:[a-zA-Z0-9-]+:(\\d{12}):function:[a-zA-Z0-9-_]+";
//Table property that we expect to contain the source table name
public static final String SOURCE_TABLE_PROPERTY = "sourceTable";
//Table property that we expect to contain the column name mapping
public static final String COLUMN_NAME_MAPPING_PROPERTY = "columnMapping";
// Table property (optional) that we expect to contain custom datetime formatting
public static final String DATETIME_FORMAT_MAPPING_PROPERTY = "datetimeFormatMapping";
// Table property (optional) that we will create from DATETIME_FORMAT_MAPPING_PROPERTY with normalized column names
public static final String DATETIME_FORMAT_MAPPING_PROPERTY_NORMALIZED = "datetimeFormatMappingNormalized";
public static final String VIEW_METADATA_FIELD = "_view_template";
// Metadata for indicating whether or not the glue table contained a set or decimal type.
// This is needed because we did not used to support these types in the GlueLexer/Parser.
// Now that we do, some connectors (like the DDB Connector) needs this information in order to
// emulate behavior from prior versions.
public static final String GLUE_TABLE_CONTAINS_PREVIOUSLY_UNSUPPORTED_TYPE = "glueTableContainsPreviouslyUnsupportedType";
private final AWSGlue awsGlue;
/**
* Basic constructor which is recommended when extending this class.
*
* @param sourceType The source type, used in diagnostic logging.
* @param configOptions The configOptions for this MetadataHandler.
*/
public GlueMetadataHandler(String sourceType, java.util.Map configOptions)
{
super(sourceType, configOptions);
// This logic is messy with a double negatives but this is how it was done before so
// we need to maintain backwards compatibility.
//
// Original comment: "Disable Glue if the env var is present and not explicitly set to "false""
boolean disabled = configOptions.get(DISABLE_GLUE) != null && !"false".equalsIgnoreCase(configOptions.get(DISABLE_GLUE));
// null if the current instance does not want to leverage Glue for metadata
awsGlue = disabled ? null : (AWSGlueClientBuilder.standard()
.withClientConfiguration(new ClientConfiguration().withConnectionTimeout(CONNECT_TIMEOUT))
.build());
}
/**
* Constructor that allows injection of a customized Glue client.
*
* @param awsGlue The glue client to use.
* @param sourceType The source type, used in diagnostic logging.
* @param configOptions The configOptions for this MetadataHandler.
*/
public GlueMetadataHandler(AWSGlue awsGlue, String sourceType, java.util.Map configOptions)
{
super(sourceType, configOptions);
this.awsGlue = awsGlue;
}
/**
* Full DI constructor used mostly for testing
*
* @param awsGlue The glue client to use.
* @param encryptionKeyFactory The EncryptionKeyFactory to use for spill encryption.
* @param secretsManager The AWSSecretsManager client that can be used when attempting to resolve secrets.
* @param athena The Athena client that can be used to fetch query termination status to fast-fail this handler.
* @param spillBucket The S3 Bucket to use when spilling results.
* @param spillPrefix The S3 prefix to use when spilling results.
* @param configOptions The configOptions for this MetadataHandler.
*/
@VisibleForTesting
protected GlueMetadataHandler(
AWSGlue awsGlue,
EncryptionKeyFactory encryptionKeyFactory,
AWSSecretsManager secretsManager,
AmazonAthena athena,
String sourceType,
String spillBucket,
String spillPrefix,
java.util.Map configOptions)
{
super(encryptionKeyFactory, secretsManager, athena, sourceType, spillBucket, spillPrefix, configOptions);
this.awsGlue = awsGlue;
}
/**
* Provides access to the Glue client if the extender should need it. This will return null if Glue
* use is disabled.
*
* @return The AWSGlue client being used by this class, or null if disabled.
*/
protected AWSGlue getAwsGlue()
{
return awsGlue;
}
/**
* Provides access to the current AWS Glue DataCatalog being used by this class.
*
* @param request The request for which we'd like to resolve the catalog.
* @return The glue catalog to use for the request.
*/
protected String getCatalog(MetadataRequest request)
{
String override = configOptions.get(CATALOG_NAME_ENV_OVERRIDE);
if (override == null) {
if (request.getContext() != null) {
String functionArn = request.getContext().getInvokedFunctionArn();
String functionOwner = getFunctionOwner(functionArn).orElse(null);
if (functionOwner != null) {
logger.debug("Function Owner: " + functionOwner);
return functionOwner;
}
}
return request.getIdentity().getAccount();
}
return override;
}
/**
* Returns an unfiltered list of schemas (aka databases) from AWS Glue DataCatalog.
*
* @param blockAllocator Tool for creating and managing Apache Arrow Blocks.
* @param request Provides details on who made the request and which Athena catalog they are querying.
* @return The ListSchemasResponse which mostly contains the list of schemas (aka databases).
*/
@Override
public ListSchemasResponse doListSchemaNames(BlockAllocator blockAllocator, ListSchemasRequest request)
throws Exception
{
return doListSchemaNames(blockAllocator, request, null);
}
/**
* Returns a list of schemas (aka databases) from AWS Glue DataCatalog with optional filtering.
*
* @param blockAllocator Tool for creating and managing Apache Arrow Blocks.
* @param request Provides details on who made the request and which Athena catalog they are querying.
* @param filter The DatabaseFilter to apply to all schemas (aka databases) before adding them to the results list.
* @return The ListSchemasResponse which mostly contains the list of schemas (aka databases).
*/
protected ListSchemasResponse doListSchemaNames(BlockAllocator blockAllocator, ListSchemasRequest request, DatabaseFilter filter)
throws Exception
{
GetDatabasesRequest getDatabasesRequest = new GetDatabasesRequest();
getDatabasesRequest.setCatalogId(getCatalog(request));
List schemas = new ArrayList<>();
String nextToken = null;
do {
getDatabasesRequest.setNextToken(nextToken);
GetDatabasesResult result = awsGlue.getDatabases(getDatabasesRequest);
for (Database next : result.getDatabaseList()) {
if (filter == null || filter.filter(next)) {
schemas.add(next.getName());
}
}
nextToken = result.getNextToken();
}
while (nextToken != null);
return new ListSchemasResponse(request.getCatalogName(), schemas);
}
/**
* Returns an unfiltered list of tables from AWS Glue DataCatalog for the requested schema (aka database)
*
* @param blockAllocator Tool for creating and managing Apache Arrow Blocks.
* @param request Provides details on who made the request and which Athena catalog they are querying.
* @return The ListTablesResponse which mostly contains the list of table names.
*/
@Override
public ListTablesResponse doListTables(BlockAllocator blockAllocator, ListTablesRequest request)
throws Exception
{
return doListTables(blockAllocator, request, null);
}
/**
* Returns a paginated list of tables from AWS Glue DataCatalog with optional filtering for the requested schema
* (aka database).
*
* @param blockAllocator Tool for creating and managing Apache Arrow Blocks.
* @param request Provides details on who made the request and which Athena catalog they are querying.
* @param filter The TableFilter to apply to all tables before adding them to the results list.
* @return The ListTablesResponse which mostly contains the list of table names.
* @implNote A complete (un-paginated) list of tables should be returned if the request's pageSize is set to
* ListTablesRequest.UNLIMITED_PAGE_SIZE_VALUE.
*/
protected ListTablesResponse doListTables(BlockAllocator blockAllocator, ListTablesRequest request, TableFilter filter)
throws Exception
{
GetTablesRequest getTablesRequest = new GetTablesRequest();
getTablesRequest.setCatalogId(getCatalog(request));
getTablesRequest.setDatabaseName(request.getSchemaName());
Set tables = new HashSet<>();
String nextToken = request.getNextToken();
int pageSize = request.getPageSize();
do {
getTablesRequest.setNextToken(nextToken);
if (pageSize != UNLIMITED_PAGE_SIZE_VALUE) {
// Paginated requests will include the maxResults argument determined by the minimum value between the
// pageSize and the maximum results supported by Glue (as defined in the Glue API docs).
int maxResults = Math.min(pageSize, GET_TABLES_REQUEST_MAX_RESULTS);
getTablesRequest.setMaxResults(maxResults);
pageSize -= maxResults;
}
GetTablesResult result = awsGlue.getTables(getTablesRequest);
for (Table next : result.getTableList()) {
if (filter == null || filter.filter(next)) {
tables.add(new TableName(request.getSchemaName(), next.getName()));
}
}
nextToken = result.getNextToken();
}
while (nextToken != null && (pageSize == UNLIMITED_PAGE_SIZE_VALUE || pageSize > 0));
return new ListTablesResponse(request.getCatalogName(), tables, nextToken);
}
/**
* Attempts to retrieve a Table (columns and properties) from AWS Glue for the request schema (aka database) and table
* name with no fitlering.
*
* @param blockAllocator Tool for creating and managing Apache Arrow Blocks.
* @param request Provides details on who made the request and which Athena catalog, database, and table they are querying.
* @return A GetTableResponse mostly containing the columns, their types, and any table properties for the requested table.
*/
@Override
public GetTableResponse doGetTable(BlockAllocator blockAllocator, GetTableRequest request)
throws Exception
{
return doGetTable(blockAllocator, request, null);
}
private boolean isPreviouslyUnsupported(String glueType, Field arrowField)
{
// For the set type we have to compare against the glueType String because they are represented as Lists in Arrow.
boolean currentResult = arrowField.getType().getTypeID().equals(ArrowType.ArrowTypeID.Decimal) ||
arrowField.getType().getTypeID().equals(ArrowType.ArrowTypeID.Map) ||
glueType.contains("set<");
if (!currentResult) {
// Need to recursively check the arrowField inner types
for (Field child : arrowField.getChildren()) {
if (isPreviouslyUnsupported("", child)) {
return true;
}
}
}
return currentResult;
}
/**
* Attempts to retrieve a Table (columns and properties) from AWS Glue for the request schema (aka database) and table
* name with no filtering.
*
* @param blockAllocator Tool for creating and managing Apache Arrow Blocks.
* @param request Provides details on who made the request and which Athena catalog, database, and table they are querying.
* @param filter The TableFilter to apply to any matching table before generating the result.
* @return A GetTableResponse mostly containing the columns, their types, and any table properties for the requested table.
* @note This method throws a RuntimeException if not table matching the requested criteria (and filter) is found.
*/
protected GetTableResponse doGetTable(BlockAllocator blockAllocator, GetTableRequest request, TableFilter filter)
throws Exception
{
TableName tableName = request.getTableName();
com.amazonaws.services.glue.model.GetTableRequest getTableRequest = new com.amazonaws.services.glue.model.GetTableRequest();
getTableRequest.setCatalogId(getCatalog(request));
getTableRequest.setDatabaseName(tableName.getSchemaName());
getTableRequest.setName(tableName.getTableName());
GetTableResult result = awsGlue.getTable(getTableRequest);
Table table = result.getTable();
if (filter != null && !filter.filter(table)) {
throw new RuntimeException("No matching table found " + request.getTableName());
}
SchemaBuilder schemaBuilder = SchemaBuilder.newBuilder();
if (table.getParameters() != null) {
table.getParameters()
.entrySet()
.forEach(next -> schemaBuilder.addMetadata(next.getKey(), next.getValue()));
}
//A column name mapping can be provided to get around restrictive Glue naming rules
Map columnNameMapping = getColumnNameMapping(table);
Map dateTimeFormatMapping = getDateTimeFormatMapping(table);
Map datetimeFormatMappingWithColumnName = new HashMap<>();
Set partitionCols = new HashSet<>();
if (table.getPartitionKeys() != null) {
partitionCols = table.getPartitionKeys()
.stream().map(next -> columnNameMapping.getOrDefault(next.getName(), next.getName())).collect(Collectors.toSet());
}
// partition columns should be added to the schema if they exist
List allColumns = Stream.of(table.getStorageDescriptor().getColumns(), table.getPartitionKeys() == null ? new ArrayList() : table.getPartitionKeys())
.flatMap(x -> x.stream())
.collect(Collectors.toList());
boolean glueTableContainsPreviouslyUnsupportedType = false;
for (Column next : allColumns) {
String rawColumnName = next.getName();
String mappedColumnName = columnNameMapping.getOrDefault(rawColumnName, rawColumnName);
// apply any type override provided in typeOverrideMapping from metadata
// this is currently only used for timestamp with timezone support
logger.info("Column {} with registered type {}", rawColumnName, next.getType());
Field arrowField = convertField(mappedColumnName, next.getType());
schemaBuilder.addField(arrowField);
// Add non-null non-empty comments to metadata
if (next.getComment() != null && !next.getComment().trim().isEmpty()) {
schemaBuilder.addMetadata(mappedColumnName, next.getComment());
}
if (dateTimeFormatMapping.containsKey(rawColumnName)) {
datetimeFormatMappingWithColumnName.put(mappedColumnName, dateTimeFormatMapping.get(rawColumnName));
}
// Indicate that we found a `set` or `decimal` type so that we can set this metadata on the schemaBuilder later on
if (glueTableContainsPreviouslyUnsupportedType == false && isPreviouslyUnsupported(next.getType(), arrowField)) {
glueTableContainsPreviouslyUnsupportedType = true;
}
}
populateDatetimeFormatMappingIfAvailable(schemaBuilder, datetimeFormatMappingWithColumnName);
populateSourceTableNameIfAvailable(table, schemaBuilder);
if (table.getViewOriginalText() != null && !table.getViewOriginalText().isEmpty()) {
schemaBuilder.addMetadata(VIEW_METADATA_FIELD, table.getViewOriginalText());
}
schemaBuilder.addMetadata(GLUE_TABLE_CONTAINS_PREVIOUSLY_UNSUPPORTED_TYPE, String.valueOf(glueTableContainsPreviouslyUnsupportedType));
return new GetTableResponse(request.getCatalogName(),
request.getTableName(),
schemaBuilder.build(),
partitionCols);
}
/**
* Maps a Glue field to an Apache Arrow Field.
*
* @param name The name of the field in Glue.
* @param glueType The type of the field in Glue.
* @return The corresponding Apache Arrow Field.
* @note You can override this implementation to provide your own mappings.
*/
protected Field convertField(String name, String glueType)
{
try {
return GlueFieldLexer.lex(name, glueType);
}
catch (RuntimeException ex) {
throw new RuntimeException("Error converting field[" + name + "] with type[" + glueType + "]", ex);
}
}
public interface TableFilter
{
/**
* Used to filter table results.
*
* @param table The table to evaluate.
* @return True if the provided table should be in the result, False if not.
*/
boolean filter(Table table);
}
public interface DatabaseFilter
{
/**
* Used to filter database results.
*
* @param database The database to evaluate.
* @return True if the provided database should be in the result, False if not.
*/
boolean filter(Database database);
}
/**
* Glue has strict table naming rules and may not be able to match the exact table name from the source. So this stores
* the source table name in the schema metadata if necessary to ease lookup later. It looks for it in the following places:
*
* - A table property called {@value SOURCE_TABLE_PROPERTY}
*
- In StorageDescriptor.Location in the form of an ARN (e.g. arn:aws:dynamodb:us-east-1:012345678910:table/mytable)
*
* Override this method to fetch the source table name from somewhere else.
*
* @param table The Glue Table
* @param schemaBuilder The schema being generated
*/
protected static void populateSourceTableNameIfAvailable(Table table, SchemaBuilder schemaBuilder)
{
String sourceTableProperty = table.getParameters().get(SOURCE_TABLE_PROPERTY);
if (sourceTableProperty != null) {
// table property exists so nothing to do (assumes all table properties were already copied)
return;
}
String location = table.getStorageDescriptor().getLocation();
if (location != null) {
Matcher matcher = TABLE_ARN_REGEX.matcher(location);
if (matcher.matches()) {
schemaBuilder.addMetadata(SOURCE_TABLE_PROPERTY, matcher.group(1));
}
}
}
/**
* Will return the source table name stored by {@link #populateSourceTableNameIfAvailable}
*
* @param schema The schema returned by {@link #doGetTable}
* @return The source table name
*/
protected static String getSourceTableName(Schema schema)
{
return schema.getCustomMetadata().get(SOURCE_TABLE_PROPERTY);
}
/**
* If available, will parse and return a column name mapping for cases when a data source's columns
* cannot be represented by Glue's quite restrictive naming rules. It looks a comma separated inline map
* in the {@value #COLUMN_NAME_MAPPING_PROPERTY} table property.
*
* @param table The glue table
* @return A column mapping if provided, otherwise an empty map
*/
protected static Map getColumnNameMapping(Table table)
{
String columnNameMappingParam = table.getParameters().get(COLUMN_NAME_MAPPING_PROPERTY);
if (!Strings.isNullOrEmpty(columnNameMappingParam)) {
return MAP_SPLITTER.split(columnNameMappingParam);
}
return ImmutableMap.of();
}
/**
* If available, Retrieves the map of normalized column names to customized format
* for any string representation of date/datetime
*
* @param table The glue table
* @returns a map of column name to date/datetime format that is used to parse the values in table
* if provided, otherwise an empty map
*/
private Map getDateTimeFormatMapping(Table table)
{
String datetimeFormatMappingParam = table.getParameters().get(DATETIME_FORMAT_MAPPING_PROPERTY);
if (!Strings.isNullOrEmpty(datetimeFormatMappingParam)) {
return MAP_SPLITTER.split(datetimeFormatMappingParam);
}
return ImmutableMap.of();
}
/**
* If available, adds stringified map of normalized columns to date/datetime format to Schema metadata
*
* @param schemaBuilder The schema being generated
* @param dateTimeFormatMapping map of normalized column names to date/datetime format, if provided
*/
private void populateDatetimeFormatMappingIfAvailable(SchemaBuilder schemaBuilder,
Map dateTimeFormatMapping)
{
if (dateTimeFormatMapping.size() > 0) {
String datetimeFormatMappingString = dateTimeFormatMapping.entrySet().stream()
.map(entry -> entry.getKey() + "=" + entry.getValue())
.collect(Collectors.joining(","));
schemaBuilder.addMetadata(DATETIME_FORMAT_MAPPING_PROPERTY_NORMALIZED, datetimeFormatMappingString);
}
}
/**
* Parse the function owner from a lambda function ARN
*
* @param functionArn The lambda function arn
* @returns a string of the function owner
*/
private Optional getFunctionOwner(String functionArn)
{
if (functionArn != null) {
Pattern arnPattern = Pattern.compile(FUNCTION_ARN_REGEX);
Matcher arnMatcher = arnPattern.matcher(functionArn);
try {
if (arnMatcher.matches() && arnMatcher.groupCount() > 0 && arnMatcher.group(1) != null) {
return Optional.of(arnMatcher.group(1));
}
}
catch (Exception e) {
logger.warn("Unable to parse owner from function arn: " + functionArn, e);
}
}
return Optional.empty();
}
}