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AdversarialReadPageCursor.java
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AdversarialReadPageCursor.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 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.adversaries.pagecache;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Objects;
import java.util.concurrent.ThreadLocalRandom;
import org.neo4j.adversaries.Adversary;
import org.neo4j.io.pagecache.PageCursor;
/**
* A read {@linkplain PageCursor page cursor} that wraps another page cursor and an {@linkplain Adversary adversary}
* to provide a misbehaving page cursor implementation for testing.
* <p>
* Depending on the adversary each read operation can throw either {@link RuntimeException} like
* {@link SecurityException} or {@link IOException} like {@link FileNotFoundException}.
* <p>
* Depending on the adversary each read operation can produce an inconsistent read and require caller to retry using
* while loop with {@link PageCursor#shouldRetry()} as a condition.
* <p>
* Write operations will always throw an {@link IllegalStateException} because this is a read cursor.
* See {@link org.neo4j.io.pagecache.PagedFile#PF_SHARED_LOCK} flag.
*/
@SuppressWarnings( "unchecked" )
class AdversarialReadPageCursor implements PageCursor
{
private final PageCursor delegate;
private final Adversary adversary;
private boolean currentReadIsPreparingInconsistent;
private boolean currentReadIsInconsistent;
private int callCounter;
// This field for meant to be inspected with the debugger.
@SuppressWarnings( "MismatchedQueryAndUpdateOfCollection" )
private List<Object> inconsistentReadHistory;
AdversarialReadPageCursor( PageCursor delegate, Adversary adversary )
{
this.delegate = Objects.requireNonNull( delegate );
this.adversary = Objects.requireNonNull( adversary );
}
@Override
public byte getByte()
{
return inconsistently( delegate.getByte() ).byteValue();
}
private <T extends Number> Number inconsistently( T value )
{
if ( currentReadIsPreparingInconsistent )
{
callCounter++;
return value;
}
if ( currentReadIsInconsistent && (--callCounter) <= 0 )
{
ThreadLocalRandom rng = ThreadLocalRandom.current();
long x = value.longValue();
if ( x != 0 & rng.nextBoolean() )
{
x = ~x;
}
else
{
x = rng.nextLong();
}
inconsistentReadHistory.add( new NumberValue( value.getClass(), x, delegate.getOffset() ) );
return x;
}
return value;
}
private void inconsistently( byte[] data )
{
if ( currentReadIsPreparingInconsistent )
{
callCounter++;
}
else if ( currentReadIsInconsistent )
{
ThreadLocalRandom.current().nextBytes( data );
inconsistentReadHistory.add( Arrays.copyOf( data, data.length ) );
}
}
@Override
public byte getByte( int offset )
{
return inconsistently( delegate.getByte( offset ) ).byteValue();
}
@Override
public void putByte( byte value )
{
throw new IllegalStateException( "Cannot write using read cursor" );
}
@Override
public void putByte( int offset, byte value )
{
throw new IllegalStateException( "Cannot write using read cursor" );
}
@Override
public long getLong()
{
return inconsistently( delegate.getLong() ).longValue();
}
@Override
public long getLong( int offset )
{
return inconsistently( delegate.getLong( offset ) ).longValue();
}
@Override
public void putLong( long value )
{
throw new IllegalStateException( "Cannot write using read cursor" );
}
@Override
public void putLong( int offset, long value )
{
throw new IllegalStateException( "Cannot write using read cursor" );
}
@Override
public int getInt()
{
return inconsistently( delegate.getInt() ).intValue();
}
@Override
public int getInt( int offset )
{
return inconsistently( delegate.getInt( offset ) ).intValue();
}
@Override
public void putInt( int value )
{
throw new IllegalStateException( "Cannot write using read cursor" );
}
@Override
public void putInt( int offset, int value )
{
throw new IllegalStateException( "Cannot write using read cursor" );
}
@Override
public long getUnsignedInt()
{
return inconsistently( delegate.getUnsignedInt() ).longValue();
}
@Override
public long getUnsignedInt( int offset )
{
return inconsistently( delegate.getUnsignedInt( offset ) ).longValue();
}
@Override
public void getBytes( byte[] data )
{
delegate.getBytes( data );
inconsistently( data );
}
@Override
public void putBytes( byte[] data )
{
throw new IllegalStateException( "Cannot write using read cursor" );
}
@Override
public short getShort()
{
return inconsistently( delegate.getShort() ).shortValue();
}
@Override
public short getShort( int offset )
{
return inconsistently( delegate.getShort( offset ) ).shortValue();
}
@Override
public void putShort( short value )
{
throw new IllegalStateException( "Cannot write using read cursor" );
}
@Override
public void putShort( int offset, short value )
{
throw new IllegalStateException( "Cannot write using read cursor" );
}
@Override
public void setOffset( int offset )
{
adversary.injectFailure( IndexOutOfBoundsException.class );
delegate.setOffset( offset );
}
@Override
public int getOffset()
{
return delegate.getOffset();
}
@Override
public long getCurrentPageId()
{
return delegate.getCurrentPageId();
}
@Override
public int getCurrentPageSize()
{
return delegate.getCurrentPageSize();
}
@Override
public File getCurrentFile()
{
return delegate.getCurrentFile();
}
@Override
public void rewind()
{
delegate.rewind();
}
@Override
public boolean next() throws IOException
{
currentReadIsPreparingInconsistent = adversary.injectFailureOrMischief( FileNotFoundException.class, IOException.class,
SecurityException.class, IllegalStateException.class );
callCounter = 0;
return delegate.next();
}
@Override
public boolean next( long pageId ) throws IOException
{
currentReadIsPreparingInconsistent = adversary.injectFailureOrMischief( FileNotFoundException.class, IOException.class,
SecurityException.class, IllegalStateException.class );
callCounter = 0;
return delegate.next( pageId );
}
@Override
public void close()
{
delegate.close();
}
@Override
public boolean shouldRetry() throws IOException
{
adversary.injectFailure( FileNotFoundException.class, IOException.class, SecurityException.class,
IllegalStateException.class );
if ( currentReadIsPreparingInconsistent )
{
currentReadIsPreparingInconsistent = false;
currentReadIsInconsistent = true;
callCounter = ThreadLocalRandom.current().nextInt( callCounter + 1 );
inconsistentReadHistory = new ArrayList<>();
delegate.shouldRetry();
delegate.setOffset( 0 );
return true;
}
if ( currentReadIsInconsistent )
{
currentReadIsInconsistent = false;
delegate.shouldRetry();
delegate.setOffset( 0 );
return true;
}
return delegate.shouldRetry();
}
private static class NumberValue
{
private final Class<? extends Number> type;
private final Long value;
private final int offset;
private final Exception trace;
public NumberValue( Class<? extends Number> type, Long value, int offset )
{
this.type = type;
this.value = value;
this.offset = offset;
trace = new Exception( toString() );
trace.fillInStackTrace();
}
@Override
public String toString()
{
String typeName = type.getCanonicalName();
switch ( typeName )
{
case "java.lang.Byte": return "(byte)" + value.byteValue() + " at offset " + offset;
case "java.lang.Short": return "(short)" + value.shortValue() + " at offset " + offset;
case "java.lang.Integer": return "(int)" + value.intValue() + " at offset " + offset;
case "java.lang.Long": return "(long)" + value + " at offset " + offset;
}
return "(" + typeName + ")" + value + " at offset " + offset;
}
public void printStackTrace()
{
trace.printStackTrace();
}
}
}