org.apache.hadoop.hive.ql.lockmgr.TxnManagerFactory Maven / Gradle / Ivy
/**
* 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.ql.lockmgr;
import org.apache.hadoop.hive.conf.HiveConf;
import org.apache.hadoop.hive.ql.ErrorMsg;
import org.apache.hadoop.util.ReflectionUtils;
/**
* A factory to get an instance of {@link HiveTxnManager}. This should
* always be called rather than building a transaction manager via reflection.
* This factory will read the configuration file to determine which
* transaction manager to instantiate. It will stash the chosen transaction
* manager into the Context object, and subsequently return it from there so
* that if there are multiple Hive threads running,
* each will get it's appropriate transaction manager.
*/
public class TxnManagerFactory {
private static TxnManagerFactory self;
/**
* Get the singleton instance of this factory.
* @return this factory
*/
public static synchronized TxnManagerFactory getTxnManagerFactory() {
if (self == null) {
self = new TxnManagerFactory();
}
return self;
}
/**
* Create a new transaction manager. The transaction manager to
* instantiate will be determined by the hive.txn.manager value in the
* configuration. This should not be called if a transaction manager has
* already been constructed and stored in the Context object.
* @param conf HiveConf object used to construct the transaction manager
* @return the transaction manager
* @throws LockException if there is an error constructing the transaction
* manager.
*/
public HiveTxnManager getTxnManager(HiveConf conf) throws
LockException {
HiveTxnManager txnMgr = null;
// Determine the transaction manager to use from the configuration.
String txnMgrName = conf.getVar(HiveConf.ConfVars.HIVE_TXN_MANAGER);
if (txnMgrName == null || txnMgrName.isEmpty()) {
throw new LockException(ErrorMsg.TXNMGR_NOT_SPECIFIED.getMsg());
}
// Instantiate the chosen transaction manager
try {
HiveTxnManagerImpl impl = (HiveTxnManagerImpl)ReflectionUtils.newInstance(
conf.getClassByName(txnMgrName), conf);
impl.setHiveConf(conf);
txnMgr = impl;
} catch (ClassNotFoundException e) {
throw new LockException(ErrorMsg.TXNMGR_NOT_INSTANTIATED.getMsg());
}
return txnMgr;
}
private TxnManagerFactory() {
}
}