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Recovery.java
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Recovery.java
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/*
* Copyright (c) 2002-2017 "Neo Technology,"
* Network Engine for Objects in Lund AB [http://neotechnology.com]
*
* This file is part of Neo4j.
*
* Neo4j is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.neo4j.kernel.recovery;
import java.io.IOException;
import org.neo4j.helpers.collection.Visitor;
import org.neo4j.kernel.impl.transaction.CommittedTransactionRepresentation;
import org.neo4j.kernel.impl.transaction.log.LogPosition;
import org.neo4j.kernel.impl.transaction.log.TransactionCursor;
import org.neo4j.kernel.impl.transaction.log.TransactionIdStore;
import org.neo4j.kernel.lifecycle.LifecycleAdapter;
import org.neo4j.storageengine.api.TransactionApplicationMode;
import static org.neo4j.storageengine.api.TransactionApplicationMode.RECOVERY;
import static org.neo4j.storageengine.api.TransactionApplicationMode.REVERSE_RECOVERY;
/**
* This is the process of doing a recovery on the transaction log and store, and is executed
* at startup of {@link org.neo4j.kernel.NeoStoreDataSource}.
*/
public class Recovery extends LifecycleAdapter
{
public interface Monitor
{
default void recoveryRequired( LogPosition recoveryPosition )
{ // no-op by default
}
default void transactionRecovered( long txId )
{ // no-op by default
}
default void recoveryCompleted( int numberOfRecoveredTransactions )
{ // no-op by default
}
default void reverseStoreRecoveryCompleted( long lowestRecoveredTxId )
{ // no-op by default
}
}
public interface RecoveryApplier extends Visitor<CommittedTransactionRepresentation,Exception>, AutoCloseable
{
}
public interface SPI
{
TransactionCursor getTransactions( LogPosition recoveryFromPosition ) throws IOException;
TransactionCursor getTransactionsInReverseOrder( LogPosition recoveryFromPosition ) throws IOException;
LogPosition getPositionToRecoverFrom() throws IOException;
void startRecovery();
RecoveryApplier getRecoveryApplier( TransactionApplicationMode mode ) throws Exception;
void allTransactionsRecovered( CommittedTransactionRepresentation lastRecoveredTransaction,
LogPosition positionAfterLastRecoveredTransaction ) throws Exception;
}
private final SPI spi;
private final Monitor monitor;
private int numberOfRecoveredTransactions;
private boolean recoveredLog;
public Recovery( SPI spi, Monitor monitor )
{
this.spi = spi;
this.monitor = monitor;
}
@Override
public void init() throws Throwable
{
LogPosition recoveryFromPosition = spi.getPositionToRecoverFrom();
if ( LogPosition.UNSPECIFIED.equals( recoveryFromPosition ) )
{
return;
}
monitor.recoveryRequired( recoveryFromPosition );
spi.startRecovery();
// Backwards for neo store only
long lowestRecoveredTxId = TransactionIdStore.BASE_TX_ID;
try ( TransactionCursor transactionsToRecover = spi.getTransactionsInReverseOrder( recoveryFromPosition );
RecoveryApplier recoveryVisitor = spi.getRecoveryApplier( REVERSE_RECOVERY ); )
{
while ( transactionsToRecover.next() )
{
recoveryVisitor.visit( transactionsToRecover.get() );
lowestRecoveredTxId = transactionsToRecover.get().getCommitEntry().getTxId();
}
}
monitor.reverseStoreRecoveryCompleted( lowestRecoveredTxId );
// Forward with all appliers
LogPosition recoveryToPosition;
CommittedTransactionRepresentation lastTransaction = null;
try ( TransactionCursor transactionsToRecover = spi.getTransactions( recoveryFromPosition );
RecoveryApplier recoveryVisitor = spi.getRecoveryApplier( RECOVERY ); )
{
while ( transactionsToRecover.next() )
{
lastTransaction = transactionsToRecover.get();
long txId = lastTransaction.getCommitEntry().getTxId();
recoveryVisitor.visit( lastTransaction );
monitor.transactionRecovered( txId );
numberOfRecoveredTransactions++;
}
recoveryToPosition = transactionsToRecover.position();
}
if ( recoveryToPosition.equals( LogPosition.UNSPECIFIED ) )
{
recoveryToPosition = recoveryFromPosition;
}
spi.allTransactionsRecovered( lastTransaction, recoveryToPosition );
recoveredLog = true;
}
@Override
public void start() throws Throwable
{
// This is here as by now all other services have reacted to the recovery process
if ( recoveredLog )
{
monitor.recoveryCompleted( numberOfRecoveredTransactions );
}
}
}