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PositionToRecoverFrom.java
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PositionToRecoverFrom.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.function.ThrowingLongFunction;
import org.neo4j.kernel.impl.store.UnderlyingStorageException;
import org.neo4j.kernel.impl.transaction.log.LogPosition;
import static org.neo4j.kernel.impl.transaction.log.LogVersionRepository.INITIAL_LOG_VERSION;
/**
* Utility class to find the log position to start recovery from
*/
public class PositionToRecoverFrom implements ThrowingLongFunction<LogPosition,IOException>
{
public interface Monitor
{
/**
* There's a check point log entry as the last entry in the transaction log.
*
* @param logPosition {@link LogPosition} of the last check point.
*/
default void noCommitsAfterLastCheckPoint( LogPosition logPosition )
{ // no-op by default
}
/**
* There's a check point log entry, but there are other log entries after it.
*
* @param logPosition {@link LogPosition} pointing to the first log entry after the last
* check pointed transaction.
* @param firstTxIdAfterLastCheckPoint transaction id of the first transaction after the last check point.
*/
default void commitsAfterLastCheckPoint( LogPosition logPosition, long firstTxIdAfterLastCheckPoint )
{ // no-op by default
}
/**
* No check point log entry found in the transaction log.
*/
default void noCheckPointFound()
{ // no-op by default
}
}
public static final Monitor NO_MONITOR = new Monitor()
{
};
private final LatestCheckPointFinder checkPointFinder;
private final Monitor monitor;
public PositionToRecoverFrom( LatestCheckPointFinder checkPointFinder, Monitor monitor )
{
this.checkPointFinder = checkPointFinder;
this.monitor = monitor;
}
/**
* Find the log position to start recovery from
*
* @param currentLogVersion the latest transaction log version
* @return {@link LogPosition#UNSPECIFIED} if there is no need to recover otherwise the {@link LogPosition} to
* start recovery from
* @throws IOException if log files cannot be read
*/
@Override
public LogPosition apply( long currentLogVersion ) throws IOException
{
LatestCheckPointFinder.LatestCheckPoint latestCheckPoint = checkPointFinder.find( currentLogVersion );
if ( !latestCheckPoint.commitsAfterCheckPoint )
{
monitor.noCommitsAfterLastCheckPoint(
latestCheckPoint.checkPoint != null ? latestCheckPoint.checkPoint.getLogPosition() : null );
return LogPosition.UNSPECIFIED;
}
if ( latestCheckPoint.checkPoint != null )
{
monitor.commitsAfterLastCheckPoint( latestCheckPoint.checkPoint.getLogPosition(),
latestCheckPoint.firstTxIdAfterLastCheckPoint );
return latestCheckPoint.checkPoint.getLogPosition();
}
else
{
if ( latestCheckPoint.oldestLogVersionFound != INITIAL_LOG_VERSION )
{
long fromLogVersion = Math.max( INITIAL_LOG_VERSION, latestCheckPoint.oldestLogVersionFound );
throw new UnderlyingStorageException( "No check point found in any log file from version " +
fromLogVersion + " to " + currentLogVersion );
}
monitor.noCheckPointFound();
return LogPosition.start( 0 );
}
}
}