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DurableStateStorage.java
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DurableStateStorage.java
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/*
* Copyright (c) 2002-2016 "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 Affero 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.neo4j.coreedge.raft.state;
import java.io.File;
import java.io.IOException;
import java.util.function.Supplier;
import org.neo4j.io.fs.FileSystemAbstraction;
import org.neo4j.kernel.impl.transaction.log.PhysicalFlushableChannel;
import org.neo4j.kernel.internal.DatabaseHealth;
import org.neo4j.kernel.lifecycle.LifecycleAdapter;
import org.neo4j.logging.Log;
import org.neo4j.logging.LogProvider;
public class DurableStateStorage<STATE> extends LifecycleAdapter implements StateStorage<STATE>
{
private STATE initialState;
private final File fileA;
private final File fileB;
private final FileSystemAbstraction fileSystemAbstraction;
private final ChannelMarshal<STATE> marshal;
private final Supplier<DatabaseHealth> databaseHealthSupplier;
private final int numberOfEntriesBeforeRotation;
private int numberOfEntriesWrittenInActiveFile;
private File currentStoreFile;
private PhysicalFlushableChannel currentStoreChannel;
public DurableStateStorage( FileSystemAbstraction fileSystemAbstraction, File stateDir, String name,
StateMarshal<STATE> marshal, int numberOfEntriesBeforeRotation,
Supplier<DatabaseHealth> databaseHealthSupplier, LogProvider logProvider )
throws IOException
// TODO Move file opening to start-time so that constructor doesn't need to throw exceptions
{
this.fileSystemAbstraction = fileSystemAbstraction;
this.marshal = marshal;
this.numberOfEntriesBeforeRotation = numberOfEntriesBeforeRotation;
this.databaseHealthSupplier = databaseHealthSupplier;
fileA = new File( stateDir, name + ".a" );
fileB = new File( stateDir, name + ".b" );
StateRecoveryManager<STATE> recoveryManager =
new StateRecoveryManager<>( fileSystemAbstraction, marshal );
final StateRecoveryManager.RecoveryStatus<STATE> recoveryStatus = recoveryManager.recover( fileA, fileB );
this.currentStoreFile = recoveryStatus.activeFile();
this.currentStoreChannel = new PhysicalFlushableChannel( fileSystemAbstraction.open( currentStoreFile, "rw" ) );
initialiseStoreFile( currentStoreFile );
this.initialState = recoveryStatus.recoveredState();
Log log = logProvider.getLog( getClass() );
log.info( "%s state restored, up to ordinal %d", name, marshal.ordinal( initialState ) );
}
@Override
public STATE getInitialState()
{
return initialState;
}
@Override
public synchronized void shutdown() throws Throwable
{
currentStoreChannel.close();
currentStoreChannel = null;
}
@Override
public synchronized void persistStoreData( STATE state ) throws IOException
{
try
{
if ( numberOfEntriesWrittenInActiveFile >= numberOfEntriesBeforeRotation )
{
switchStoreFile();
numberOfEntriesWrittenInActiveFile = 0;
}
marshal.marshal( state, currentStoreChannel );
currentStoreChannel.prepareForFlush().flush();
numberOfEntriesWrittenInActiveFile++;
}
catch ( IOException e )
{
databaseHealthSupplier.get().panic( e );
throw e;
}
}
protected void switchStoreFile() throws IOException
{
currentStoreChannel.close();
if ( currentStoreFile.getName().toLowerCase().endsWith( "a" ) )
{
currentStoreChannel = initialiseStoreFile( fileB );
currentStoreFile = fileB;
}
else if ( currentStoreFile.getName().toLowerCase().endsWith( "b" ) )
{
currentStoreChannel = initialiseStoreFile( fileA );
currentStoreFile = fileA;
}
}
private PhysicalFlushableChannel initialiseStoreFile( File nextStore ) throws IOException
{
if ( fileSystemAbstraction.fileExists( nextStore ) )
{
fileSystemAbstraction.truncate( nextStore, 0 );
return new PhysicalFlushableChannel( fileSystemAbstraction.open( nextStore, "rw" ) );
}
else
{
return new PhysicalFlushableChannel( fileSystemAbstraction.create( nextStore ) );
}
}
}