veghlaci05 commented on code in PR #4384: URL: https://github.com/apache/hive/pull/4384#discussion_r1310003447
########## standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/txn/retryhandling/DataSourceWrapper.java: ########## @@ -0,0 +1,287 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you 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. + */ +package org.apache.hadoop.hive.metastore.txn.retryhandling; + +import org.apache.hadoop.hive.metastore.DatabaseProduct; +import org.apache.hadoop.hive.metastore.api.MetaException; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; +import org.springframework.jdbc.core.ResultSetExtractor; +import org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate; +import org.springframework.jdbc.core.namedparam.SqlParameterSource; +import org.springframework.jdbc.datasource.DataSourceTransactionManager; +import org.springframework.jdbc.datasource.DataSourceUtils; +import org.springframework.transaction.PlatformTransactionManager; +import org.springframework.transaction.TransactionDefinition; +import org.springframework.transaction.TransactionException; +import org.springframework.transaction.TransactionStatus; + +import javax.sql.DataSource; +import java.sql.Connection; +import java.sql.ResultSet; +import java.util.HashMap; +import java.util.Map; +import java.util.Objects; +import java.util.function.Function; + +/** + * Wraps multiple {@link DataSource}s into a single object and offers transaction management functionality. + * Allows access of the {@link NamedParameterJdbcTemplate}, {@link Connection} objects associated with the wrapped datasources. + */ +public class DataSourceWrapper { + + private static final Logger LOG = LoggerFactory.getLogger(DataSourceWrapper.class); + private static final ThreadLocal<RetryContext> threadLocal = new ThreadLocal<>(); + + private final Map<String, DataSource> dataSources; + private final Map<String, PlatformTransactionManager> transactionManagers = new HashMap<>(); + private final Map<String, NamedParameterJdbcTemplate> jdbcTemplates = new HashMap<>(); + private final DatabaseProduct databaseProduct; + + /** + * Creates a new isntance of the {@link DataSourceWrapper} class + * @param dataSources A {@link Map} of the datasource names and the corresponding datasources which needs to be wrapped + * by this instance + * @param databaseProduct A {@link DatabaseProduct} instance representing the type of the underlying HMS dabatabe. + */ + public DataSourceWrapper(Map<String, DataSource> dataSources, DatabaseProduct databaseProduct) { + this.dataSources = dataSources; + for(String dataSource : dataSources.keySet()) { + NamedParameterJdbcTemplate jdbcTemplate = new NamedParameterJdbcTemplate(dataSources.get(dataSource)); + jdbcTemplates.put(dataSource, jdbcTemplate); + transactionManagers.put(dataSource, new DataSourceTransactionManager(Objects.requireNonNull(jdbcTemplate.getJdbcTemplate().getDataSource()))); + } + this.databaseProduct = databaseProduct; + } + + + /** + * Provides direct access to the {@link TransactionStatus} to allow manual savepoint creation, rollback, etc. + * Can be called only within an established {@link RetryContext}. + * @return Returns the {@link TransactionStatus} instance stored in the {@link RetryContext}. + * @throws IllegalStateException Thrown when called outside a {@link RetryContext}. + */ + public TransactionStatus getTransactionStatus() { + return RetryContext.getRetryContext().transactionStatus; + } + + /** + * @return Returns true if the current {@link Thread} has an associated {@link RetryContext}, false otherwise. + */ + boolean hasRetryContext() { + return threadLocal.get() != null; + } + + /** + * @return Returns the {@link NamedParameterJdbcTemplate} associated with the current {@link RetryContext}. + * Can be called only within an established {@link RetryContext}. + * @throws IllegalStateException Thrown when called outside a {@link RetryContext}. + */ + public NamedParameterJdbcTemplate getJdbcTemplate() { + return jdbcTemplates.get(RetryContext.getRetryContext().datasource); + } + + /** + * Gets a connection to the {@link DataSource} associated with the current {@link RetryContext}. Ensures that the same + * instance is returned all the time within a particular transaction. Can be called only within an established + * {@link RetryContext}. + * @return Returns a connection to the datasource. + * @throws IllegalArgumentException Thrown when called outside a {@link RetryContext} + */ + public Connection getConnection() { + return DataSourceUtils.getConnection(dataSources.get(RetryContext.getRetryContext().datasource)); + } + + /** + * @return Returns a {@link DatabaseProduct} instance representing the type of the underlying HMS dabatabe. + */ + public DatabaseProduct getDatabaseProduct() { + return databaseProduct; + } + + /** + * <p>Establishes a {@link RetryContext} on the current {@link Thread}: Creates a new transaction with the given + * {@link TransactionDefinition} using an internal {@link PlatformTransactionManager} associated with the reffered + * {@link DataSource}. Returns a {@link TransactionStatus} representing the created transaction. The returned + * {@link TransactionStatus} instance can be used for manual transaction handling.</p> + * <br> + * <p>!!!! Please note that if there already is a {@link RetryContext} established, this call will create a nested</p> + * {@link RetryContext} (and transaction).</b> + * @param definition The {@link TransactionDefinition} to use for creating a new transaction. + * @param dataSource The identifier of the {@link DataSource} to use + * @return Returns a {@link TransactionStatus} object representing the created transaction. + * @throws TransactionException Forwarded from {@link PlatformTransactionManager#getTransaction(TransactionDefinition)} + */ + public TransactionStatus getTransactionWithinRetryContext(TransactionDefinition definition, String dataSource) throws TransactionException { + TransactionStatus status = transactionManagers.get(dataSource).getTransaction(definition); + RetryContext.setRetryContext(status, dataSource); + return status; + } + + /** + * Commits the transaction associated with the current {@link Thread} and clears the {@link RetryContext}. + * Can be called only within an established {@link RetryContext}. + * @throws TransactionException Forwarded from {@link PlatformTransactionManager#commit(TransactionStatus)} + * @throws IllegalArgumentException Thrown when called outside a {@link RetryContext} + */ + public void commit() throws TransactionException { + try { + RetryContext context = RetryContext.getRetryContext(); + transactionManagers.get(context.datasource).commit(context.transactionStatus); Review Comment: The context is also required to obtain the txn manager `(transactionManagers.get(context.datasource)`, so using the helper method would lead to querying the `RetryContect` twice. -- This is an automated message from the Apache Git Service. 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