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/*
* Copyright 2006-2012 Amazon Technologies, Inc. or its affiliates.
* Amazon, Amazon.com and Carbonado are trademarks or registered trademarks
* of Amazon Technologies, Inc. or its affiliates. All rights reserved.
*
* 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.
*/
package com.amazon.carbonado.txn;
import java.util.concurrent.TimeUnit;
import com.amazon.carbonado.IsolationLevel;
import com.amazon.carbonado.PersistException;
import com.amazon.carbonado.Transaction;
/**
* Pairs two transaction together into one. The transaction cannot be atomic,
* however. Inconsistencies can result if the primary transaction succeeds in
* committing, but the secondary fails. Therefore, the designated primary
* transaction should be the one that is more likely to fail. For example, the
* primary transaction might rely on the network, but the secondary operates
* locally.
*
* @author Don Schneider
* @author Brian S O'Neill
*/
public class TransactionPair implements Transaction {
private final Transaction mPrimaryTransaction;
private final Transaction mSecondaryTransaction;
/**
* @param primaryTransaction is committed first, exited last
* @param secondaryTransaction is exited first, commited last
*/
public TransactionPair(Transaction primaryTransaction, Transaction secondaryTransaction) {
mPrimaryTransaction = primaryTransaction;
mSecondaryTransaction = secondaryTransaction;
}
public void commit() throws PersistException {
mPrimaryTransaction.commit();
try {
mSecondaryTransaction.commit();
} catch (Exception e) {
throw new PersistException
("Failure to commit secondary transaction has likely caused an inconsistency", e);
}
}
public void exit() throws PersistException {
try {
mSecondaryTransaction.exit();
} finally {
// Do this second so if there is an exception, the user sees the
// primary exception, which is presumably more important.
mPrimaryTransaction.exit();
}
}
public void setForUpdate(boolean forUpdate) {
mPrimaryTransaction.setForUpdate(forUpdate);
mSecondaryTransaction.setForUpdate(forUpdate);
}
public boolean isForUpdate() {
return mPrimaryTransaction.isForUpdate() && mSecondaryTransaction.isForUpdate();
}
public void setDesiredLockTimeout(int timeout, TimeUnit unit) {
mPrimaryTransaction.setDesiredLockTimeout(timeout, unit);
mSecondaryTransaction.setDesiredLockTimeout(timeout, unit);
}
public IsolationLevel getIsolationLevel() {
return mPrimaryTransaction.getIsolationLevel()
.lowestCommon(mSecondaryTransaction.getIsolationLevel());
}
public void detach() {
mPrimaryTransaction.detach();
try {
mSecondaryTransaction.detach();
} catch (IllegalStateException e) {
mPrimaryTransaction.attach();
throw e;
}
}
public void attach() {
mPrimaryTransaction.attach();
try {
mSecondaryTransaction.attach();
} catch (IllegalStateException e) {
mPrimaryTransaction.detach();
throw e;
}
}
public boolean preCommit() throws PersistException {
return mPrimaryTransaction.preCommit() ? mSecondaryTransaction.preCommit() : false;
}
}
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