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IdFile.java
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IdFile.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.impl.store.id;
import java.io.File;
import java.io.IOException;
import java.nio.ByteBuffer;
import org.neo4j.io.fs.FileSystemAbstraction;
import org.neo4j.io.fs.StoreChannel;
import org.neo4j.kernel.impl.store.InvalidIdGeneratorException;
import org.neo4j.kernel.impl.store.UnderlyingStorageException;
public class IdFile
{
static final long NO_RESULT = -1;
// sticky(byte), nextFreeId(long)
private static final int HEADER_SIZE = Byte.BYTES + Long.BYTES;
// if sticky the id generator wasn't closed properly so it has to be
// rebuilt (go through the node, relationship, property, rel type etc files)
private static final byte CLEAN_GENERATOR = (byte) 0;
private static final byte STICKY_GENERATOR = (byte) 1;
private final File file;
private final FileSystemAbstraction fs;
private StoreChannel fileChannel;
private boolean closed = true;
private final int grabSize;
private final boolean aggressiveReuse;
private FreeIdKeeper freeIdKeeper;
private long initialHighId;
IdFile( FileSystemAbstraction fs, File file, int grabSize, boolean aggressiveReuse )
{
if ( grabSize < 1 )
{
throw new IllegalArgumentException( "Illegal grabSize: " + grabSize );
}
this.file = file;
this.fs = fs;
this.grabSize = grabSize;
this.aggressiveReuse = aggressiveReuse;
}
// initialize the id generator and performs a simple validation
void init()
{
try
{
fileChannel = fs.open( file, "rw" );
initialHighId = readAndValidateHeader();
markAsSticky();
this.freeIdKeeper = new FreeIdKeeper( fileChannel, grabSize, aggressiveReuse, HEADER_SIZE );
closed = false;
}
catch ( IOException e )
{
throw new UnderlyingStorageException( "Unable to init id file " + file, e );
}
}
public boolean isClosed()
{
return closed;
}
long getInitialHighId()
{
return initialHighId;
}
void assertStillOpen()
{
if ( closed )
{
throw new IllegalStateException( "Closed id file " + file );
}
}
private long readAndValidateHeader() throws IOException
{
try
{
return readAndValidate( fileChannel, file );
}
catch ( InvalidIdGeneratorException e )
{
fileChannel.close();
throw e;
}
}
private static long readAndValidate( StoreChannel channel, File fileName ) throws IOException
{
ByteBuffer buffer = ByteBuffer.allocate( HEADER_SIZE );
int read = channel.read( buffer );
if ( read != HEADER_SIZE )
{
throw new InvalidIdGeneratorException(
"Unable to read header, bytes read: " + read );
}
buffer.flip();
byte storageStatus = buffer.get();
if ( storageStatus != CLEAN_GENERATOR )
{
throw new InvalidIdGeneratorException( "Id file not properly shutdown [ " +
fileName + " ], delete this id file and build a new one" );
}
return buffer.getLong();
}
static long readHighId( FileSystemAbstraction fileSystem, File file ) throws IOException
{
try ( StoreChannel channel = fileSystem.open( file, "r" ) )
{
return readAndValidate( channel, file );
}
}
private void markAsSticky() throws IOException
{
ByteBuffer buffer = ByteBuffer.allocate( Byte.BYTES );
buffer.put( STICKY_GENERATOR ).flip();
fileChannel.position( 0 );
fileChannel.write( buffer );
fileChannel.force( false );
}
private void markAsCleanlyClosed( ) throws IOException
{
// remove sticky
ByteBuffer buffer = ByteBuffer.allocate( Byte.BYTES );
buffer.put( CLEAN_GENERATOR ).flip();
fileChannel.position( 0 );
fileChannel.write( buffer );
}
public void close( long highId )
{
if ( !closed )
{
try
{
freeIdKeeper.close();
writeHeader( highId );
markAsCleanlyClosed();
closeChannel();
}
catch ( IOException e )
{
throw new UnderlyingStorageException( "Unable to close id file " + file, e );
}
}
}
private void closeChannel() throws IOException
{
fileChannel.force( false );
fileChannel.close();
fileChannel = null;
closed = true;
}
private void writeHeader( long highId ) throws IOException
{
ByteBuffer buffer = ByteBuffer.allocate( HEADER_SIZE );
buffer.put( STICKY_GENERATOR ).putLong( highId ).flip();
fileChannel.position( 0 );
fileChannel.write( buffer );
}
public void delete()
{
if ( !closed )
{
try
{
closeChannel();
}
catch ( IOException e )
{
throw new UnderlyingStorageException( "Unable to close id file " + file, e );
}
}
if ( !fs.deleteFile( file ) )
{
throw new UnderlyingStorageException( "Unable to delete id file " + file );
}
}
/**
* @return next free id or {@link IdFile#NO_RESULT} if not available
*/
long getReusableId()
{
return freeIdKeeper.getId();
}
public void freeId( long id )
{
freeIdKeeper.freeId( id );
}
long getFreeIdCount()
{
return freeIdKeeper.getCount();
}
/**
* Creates a new id file.
*
* @param file The name of the id generator
* @param throwIfFileExists if {@code true} will cause an {@link IllegalStateException} to be thrown if
* the file already exists. if {@code false} will truncate the file writing the header in it.
*/
static void createEmptyIdFile( FileSystemAbstraction fs, File file, long highId, boolean throwIfFileExists )
{
// sanity checks
if ( fs == null )
{
throw new IllegalArgumentException( "Null filesystem" );
}
if ( file == null )
{
throw new IllegalArgumentException( "Null filename" );
}
if ( throwIfFileExists && fs.fileExists( file ) )
{
throw new IllegalStateException( "Can't create id file [" + file + "], file already exists" );
}
try ( StoreChannel channel = fs.create( file ) )
{
// write the header
channel.truncate( 0 );
ByteBuffer buffer = ByteBuffer.allocate( HEADER_SIZE );
buffer.put( CLEAN_GENERATOR ).putLong( highId ).flip();
channel.write( buffer );
channel.force( false );
}
catch ( IOException e )
{
throw new UnderlyingStorageException( "Unable to create id file " + file, e );
}
}
@Override
public String toString()
{
return "IdFile{" + "file=" + file + ", fs=" + fs + ", fileChannel=" + fileChannel + ", defragCount=" +
freeIdKeeper.getCount() + ", grabSize=" + grabSize + ", aggressiveReuse=" +
aggressiveReuse + ", closed=" + closed + '}';
}
}