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BlockBasedIndexPopulator.java
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BlockBasedIndexPopulator.java
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/*
* Copyright (c) 2002-2019 "Neo4j,"
* Neo4j Sweden AB [http://neo4j.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.index.schema;
import java.io.Closeable;
import java.io.File;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.stream.Collectors;
import org.neo4j.cursor.RawCursor;
import org.neo4j.index.internal.gbptree.Hit;
import org.neo4j.index.internal.gbptree.Writer;
import org.neo4j.io.ByteUnit;
import org.neo4j.io.IOUtils;
import org.neo4j.io.fs.FileSystemAbstraction;
import org.neo4j.io.pagecache.PageCache;
import org.neo4j.kernel.api.exceptions.index.IndexEntryConflictException;
import org.neo4j.kernel.api.index.IndexDirectoryStructure;
import org.neo4j.kernel.api.index.IndexEntryUpdate;
import org.neo4j.kernel.api.index.IndexProvider;
import org.neo4j.kernel.api.index.IndexUpdater;
import org.neo4j.kernel.impl.api.index.BatchingMultipleIndexPopulator;
import org.neo4j.kernel.impl.api.index.PhaseTracker;
import org.neo4j.kernel.impl.index.schema.config.IndexSpecificSpaceFillingCurveSettingsCache;
import org.neo4j.kernel.impl.index.schema.config.SpaceFillingCurveSettingsWriter;
import org.neo4j.memory.LocalMemoryTracker;
import org.neo4j.storageengine.api.schema.PopulationProgress;
import org.neo4j.storageengine.api.schema.StoreIndexDescriptor;
import org.neo4j.util.FeatureToggles;
import org.neo4j.util.Preconditions;
import org.neo4j.values.storable.Value;
import static org.neo4j.helpers.collection.Iterables.first;
import static org.neo4j.kernel.impl.index.schema.NativeIndexUpdater.initializeKeyFromUpdate;
import static org.neo4j.kernel.impl.index.schema.NativeIndexes.deleteIndex;
public abstract class BlockBasedIndexPopulator<KEY extends NativeIndexKey<KEY>,VALUE extends NativeIndexValue> extends NativeIndexPopulator<KEY,VALUE>
{
/**
* Base size of blocks of entries. As entries gets written to a BlockStorage, they are buffered up to this size, then sorted and written out.
* As blocks gets merged into bigger blocks, this is still the size of the read buffer for each block no matter its size.
* Each thread has its own buffer when writing and each thread has {@link #MERGE_FACTOR} buffers when merging.
* The memory usage will be at its biggest during merge and a total memory usage sum can be calculated like so:
*
* {@link #BLOCK_SIZE} * numberOfThreads * {@link #MERGE_FACTOR}
*
* where typically {@link BatchingMultipleIndexPopulator} controls the number of threads. The setting
* `unsupported.dbms.multi_threaded_schema_index_population_enabled` controls whether or not the multi-threaded {@link BatchingMultipleIndexPopulator}
* is used or not, otherwise a single-threaded populator is used instead.
*/
private static final String BLOCK_SIZE = FeatureToggles.getString( BlockBasedIndexPopulator.class, "blockSize", "1M" );
/**
* When merging all blocks together the algorithm does multiple passes over the block storage, until the number of blocks reaches 1.
* Every pass does one or more merges and every merge merges up to {@link #MERGE_FACTOR} number of blocks into one block,
* i.e. the number of blocks shrinks by a factor {@link #MERGE_FACTOR} every pass, until one blocks is left.
*/
private static final int MERGE_FACTOR = FeatureToggles.getInteger( BlockBasedIndexPopulator.class, "mergeFactor", 8 );
private final IndexDirectoryStructure directoryStructure;
private final boolean archiveFailedIndex;
private final int blockSize;
private final int mergeFactor;
private final BlockStorage.Monitor blockStorageMonitor;
// written to in a synchronized method when creating new thread-local instances, read from when population completes
private final List<ThreadLocalBlockStorage> allScanUpdates = new CopyOnWriteArrayList<>();
private final ThreadLocal<ThreadLocalBlockStorage> scanUpdates;
private final ByteBufferFactory bufferFactory = new UnsafeDirectByteBufferFactory( new LocalMemoryTracker() /*plug in actual tracker when available*/ );
private IndexUpdateStorage<KEY,VALUE> externalUpdates;
// written in a synchronized method when creating new thread-local instances, read when processing external updates
private volatile boolean scanCompleted;
private final CloseCancellation cancellation = new CloseCancellation();
// Will be instantiated right before merging and can be used to neatly await merge to complete
private volatile CountDownLatch mergeOngoingLatch;
// progress state
private volatile long numberOfAppliedScanUpdates;
private volatile long numberOfAppliedExternalUpdates;
BlockBasedIndexPopulator( PageCache pageCache, FileSystemAbstraction fs, File file, IndexLayout<KEY,VALUE> layout, IndexProvider.Monitor monitor,
StoreIndexDescriptor descriptor, IndexSpecificSpaceFillingCurveSettingsCache spatialSettings,
IndexDirectoryStructure directoryStructure, boolean archiveFailedIndex )
{
this( pageCache, fs, file, layout, monitor, descriptor, spatialSettings, directoryStructure, archiveFailedIndex, parseBlockSize(), MERGE_FACTOR,
BlockStorage.Monitor.NO_MONITOR );
}
BlockBasedIndexPopulator( PageCache pageCache, FileSystemAbstraction fs, File file, IndexLayout<KEY,VALUE> layout, IndexProvider.Monitor monitor,
StoreIndexDescriptor descriptor, IndexSpecificSpaceFillingCurveSettingsCache spatialSettings,
IndexDirectoryStructure directoryStructure, boolean archiveFailedIndex, int blockSize, int mergeFactor, BlockStorage.Monitor blockStorageMonitor )
{
super( pageCache, fs, file, layout, monitor, descriptor, new SpaceFillingCurveSettingsWriter( spatialSettings ) );
this.directoryStructure = directoryStructure;
this.archiveFailedIndex = archiveFailedIndex;
this.blockSize = blockSize;
this.mergeFactor = mergeFactor;
this.blockStorageMonitor = blockStorageMonitor;
this.scanUpdates = ThreadLocal.withInitial( this::newThreadLocalBlockStorage );
}
private synchronized ThreadLocalBlockStorage newThreadLocalBlockStorage()
{
Preconditions.checkState( !cancellation.cancelled(), "Already closed" );
Preconditions.checkState( !scanCompleted, "Scan has already been completed" );
try
{
int id = allScanUpdates.size();
ThreadLocalBlockStorage blockStorage = new ThreadLocalBlockStorage( id );
allScanUpdates.add( blockStorage );
return blockStorage;
}
catch ( IOException e )
{
throw new UncheckedIOException( e );
}
}
private static int parseBlockSize()
{
long blockSize = ByteUnit.parse( BLOCK_SIZE );
Preconditions.checkArgument( blockSize >= 20 && blockSize < Integer.MAX_VALUE, "Block size need to fit in int. Was " + blockSize );
return (int) blockSize;
}
@Override
public void create()
{
try
{
deleteIndex( fileSystem, directoryStructure, descriptor.getId(), archiveFailedIndex );
}
catch ( IOException e )
{
throw new UncheckedIOException( e );
}
super.create();
try
{
externalUpdates = new IndexUpdateStorage<>( layout, fileSystem, new File( storeFile.getParent(), storeFile.getName() + ".ext" ),
bufferFactory, blockSize );
}
catch ( IOException e )
{
throw new UncheckedIOException( e );
}
}
@Override
public void add( Collection<? extends IndexEntryUpdate<?>> updates )
{
if ( !updates.isEmpty() )
{
BlockStorage<KEY,VALUE> blockStorage = scanUpdates.get().blockStorage;
for ( IndexEntryUpdate<?> update : updates )
{
storeUpdate( update, blockStorage );
}
}
}
private void storeUpdate( long entityId, Value[] values, BlockStorage<KEY,VALUE> blockStorage )
{
try
{
KEY key = layout.newKey();
VALUE value = layout.newValue();
initializeKeyFromUpdate( key, entityId, values );
value.from( values );
blockStorage.add( key, value );
}
catch ( IOException e )
{
throw new UncheckedIOException( e );
}
}
private void storeUpdate( IndexEntryUpdate<?> update, BlockStorage<KEY,VALUE> blockStorage )
{
storeUpdate( update.getEntityId(), update.values(), blockStorage );
}
private synchronized boolean markMergeStarted()
{
scanCompleted = true;
if ( cancellation.cancelled() )
{
return false;
}
mergeOngoingLatch = new CountDownLatch( 1 );
return true;
}
@Override
public void scanCompleted( PhaseTracker phaseTracker ) throws IndexEntryConflictException
{
if ( !markMergeStarted() )
{
// This populator has already been closed, either from an external cancel or drop call.
// Either way we're not supposed to do this merge.
return;
}
try
{
phaseTracker.enterPhase( PhaseTracker.Phase.MERGE );
if ( !allScanUpdates.isEmpty() )
{
ExecutorService executorService = Executors.newFixedThreadPool( allScanUpdates.size() );
List<Future<?>> mergeFutures = new ArrayList<>();
for ( ThreadLocalBlockStorage part : allScanUpdates )
{
BlockStorage<KEY,VALUE> scanUpdates = part.blockStorage;
mergeFutures.add( executorService.submit( () ->
{
scanUpdates.doneAdding();
scanUpdates.merge( mergeFactor, cancellation );
return null;
} ) );
}
executorService.shutdown();
while ( !executorService.awaitTermination( 1, TimeUnit.SECONDS ) )
{
// just wait longer
}
// Let potential exceptions in the merge threads have a chance to propagate
for ( Future<?> mergeFuture : mergeFutures )
{
mergeFuture.get();
}
}
externalUpdates.doneAdding();
// don't merge and sort the external updates
// Build the tree from the scan updates
phaseTracker.enterPhase( PhaseTracker.Phase.BUILD );
writeScanUpdatesToTree();
// Apply the external updates
phaseTracker.enterPhase( PhaseTracker.Phase.APPLY_EXTERNAL );
writeExternalUpdatesToTree();
}
catch ( IOException e )
{
throw new UncheckedIOException( e );
}
catch ( InterruptedException e )
{
Thread.currentThread().interrupt();
throw new RuntimeException( "Got interrupted, so merge not completed", e );
}
catch ( ExecutionException e )
{
// Propagating merge exception from other thread
Throwable executionException = e.getCause();
if ( executionException instanceof RuntimeException )
{
throw (RuntimeException) executionException;
}
throw new RuntimeException( executionException );
}
finally
{
mergeOngoingLatch.countDown();
}
}
/**
* We will loop over all external updates once to add them to the tree. This is done without checking any uniqueness.
* If index is a uniqueness index we will then loop over external updates again and for each ADD or CHANGED update
* we will verify that those entries are unique in the tree and throw as soon as we find a duplicate.
* @throws IOException If something goes wrong while reading from index.
* @throws IndexEntryConflictException If a duplicate is found.
*/
private void writeExternalUpdatesToTree() throws IOException, IndexEntryConflictException
{
try ( Writer<KEY,VALUE> writer = tree.writer();
IndexUpdateCursor<KEY,VALUE> updates = externalUpdates.reader() )
{
while ( updates.next() && !cancellation.cancelled() )
{
switch ( updates.updateMode() )
{
case ADDED:
writer.put( updates.key(), updates.value() );
break;
case REMOVED:
writer.remove( updates.key() );
break;
case CHANGED:
writer.remove( updates.key() );
writer.put( updates.key2(), updates.value() );
break;
default:
throw new IllegalArgumentException( "Unknown update mode " + updates.updateMode() );
}
numberOfAppliedExternalUpdates++;
}
}
if ( descriptor.isUnique() )
{
verifyUniquenessOnExternalUpdates();
}
}
/**
* When this method is called, all updates have been applied to the tree. Here we loop over all updates again and for each update we verify that in the
* end there are no duplicate entries for the value of the update update value in the tree. If intermediate duplicates was seen while applying the
* updates, that is fine as long as the tree is completely unique now. Note that only updates that result in adding a new key to the tree can possible
* cause a duplication to appear.
* @throws IOException If something goes wrong while reading from index.
* @throws IndexEntryConflictException If a duplicate is found.
*/
private void verifyUniquenessOnExternalUpdates() throws IOException, IndexEntryConflictException
{
try ( IndexUpdateCursor<KEY,VALUE> updates = externalUpdates.reader() )
{
while ( updates.next() && !cancellation.cancelled() )
{
RawCursor<Hit<KEY,VALUE>,IOException> seek;
switch ( updates.updateMode() )
{
case ADDED:
updates.key().setCompareId( false );
seek = tree.seek( updates.key(), updates.key() );
break;
case CHANGED:
updates.key2().setCompareId( false );
seek = tree.seek( updates.key2(), updates.key2() );
break;
case REMOVED:
// Can't cause uniqueness conflict
seek = null;
break;
default:
throw new IllegalArgumentException( "Unknown update mode " + updates.updateMode() );
}
verifyUniqueSeek( seek );
}
}
}
private void verifyUniqueSeek( RawCursor<Hit<KEY,VALUE>,IOException> seek ) throws IOException, IndexEntryConflictException
{
if ( seek != null )
{
if ( seek.next() )
{
long firstEntityId = seek.get().key().getEntityId();
if ( seek.next() )
{
long secondEntityId = seek.get().key().getEntityId();
throw new IndexEntryConflictException( firstEntityId, secondEntityId, seek.get().key().asValues() );
}
}
}
}
private void writeScanUpdatesToTree() throws IOException, IndexEntryConflictException
{
ConflictDetectingValueMerger<KEY,VALUE> conflictDetector = getMainConflictDetector();
try ( MergingBlockEntryReader<KEY,VALUE> allEntries = new MergingBlockEntryReader<>( layout ) )
{
for ( ThreadLocalBlockStorage part : allScanUpdates )
{
try ( BlockReader<KEY,VALUE> reader = part.blockStorage.reader() )
{
BlockEntryReader<KEY,VALUE> singleMergedBlock = reader.nextBlock();
if ( singleMergedBlock != null )
{
allEntries.addSource( singleMergedBlock );
if ( reader.nextBlock() != null )
{
throw new IllegalStateException( "Final BlockStorage had multiple blocks" );
}
}
}
}
int asMuchAsPossibleToTheLeft = 1;
try ( Writer<KEY,VALUE> writer = tree.writer( asMuchAsPossibleToTheLeft ) )
{
while ( allEntries.next() && !cancellation.cancelled() )
{
conflictDetector.controlConflictDetection( allEntries.key() );
writer.merge( allEntries.key(), allEntries.value(), conflictDetector );
if ( conflictDetector.wasConflicting() )
{
conflictDetector.reportConflict( allEntries.key().asValues() );
}
numberOfAppliedScanUpdates++;
}
}
}
}
@Override
public IndexUpdater newPopulatingUpdater()
{
if ( scanCompleted )
{
// Will need the reader from newReader, which a sub-class of this class implements
return super.newPopulatingUpdater();
}
return new IndexUpdater()
{
private volatile boolean closed;
@Override
public void process( IndexEntryUpdate<?> update )
{
assertOpen();
try
{
externalUpdates.add( update );
}
catch ( IOException e )
{
throw new UncheckedIOException( e );
}
}
@Override
public void close()
{
closed = true;
}
private void assertOpen()
{
if ( closed )
{
throw new IllegalStateException( "Updater has been closed" );
}
}
};
}
@Override
public synchronized void drop()
{
try
{
closeBlockStorage();
}
finally
{
super.drop();
}
}
@Override
public synchronized void close( boolean populationCompletedSuccessfully )
{
try
{
closeBlockStorage();
}
finally
{
bufferFactory.close();
super.close( populationCompletedSuccessfully );
}
}
// Always called from synchronized method
private void closeBlockStorage()
{
// This method may be called while scanCompleted is running. This could be a drop or shutdown(?) which happens when this population
// is in its final stages. scanCompleted merges things in multiple threads. Those threads will abort when they see that setCancel
// has been called.
cancellation.setCancel();
// If there's a merge concurrently running it will very soon notice the cancel request and abort whatever it's doing as soon as it can.
// Let's wait for that merge to be fully aborted by simply waiting for the merge latch.
if ( mergeOngoingLatch != null )
{
try
{
// We want to await any ongoing merge because it becomes problematic to close the channels otherwise
mergeOngoingLatch.await();
}
catch ( InterruptedException e )
{
Thread.currentThread().interrupt();
// We still want to go ahead and try to close things properly, so get by only restoring the interrupt flag on the thread
}
}
List<Closeable> toClose = allScanUpdates.stream().map( local -> local.blockStorage ).collect( Collectors.toCollection( ArrayList::new ) );
toClose.add( externalUpdates );
IOUtils.closeAllUnchecked( toClose );
}
@Override
public PopulationProgress progress( PopulationProgress scanProgress )
{
// A general note on scanProgress.getTotal(). Before the scan is completed most progress parts will base their estimates on that value.
// It is known that it may be slightly higher since it'll be based on store high-id, not the actual count.
// This is fine, but it creates this small "jump" in the progress in the middle somewhere when it switches from scan to merge.
// This also exists in the most basic population progress reports, but there it will be less visible since it will jump from
// some close-to-100 percentage to 100% and ONLINE.
// This progress report will consist of a couple of smaller parts, weighted differently based on empirically collected values.
// The weights will not be absolutely correct in all environments, but they don't have to be either, it will just result in some
// slices of the percentage progression range progressing at slightly different paces. However, progression of progress reporting
// naturally fluctuates anyway due to data set and I/O etc. so this is not an actual problem.
PopulationProgress.MultiBuilder builder = PopulationProgress.multiple();
// Add scan progress (this one weights a bit heavier than the others)
builder.add( scanProgress, 4 );
// Add merge progress
if ( !allScanUpdates.isEmpty() )
{
// The parts are merged in parallel so just take the first one and it will represent the whole merge progress.
// It will be fairly accurate, but slightly off sometimes if other threads gets scheduling problems, i.e. if this part
// finish far apart from others.
long completed = 0;
long total = 0;
if ( scanCompleted )
{
// We know the actual entry count to write during merge since we have been monitoring those values
ThreadLocalBlockStorage part = first( allScanUpdates );
completed = part.entriesMerged;
total = part.totalEntriesToMerge;
}
builder.add( PopulationProgress.single( completed, total ), 1 );
}
// Add tree building incl. external updates
PopulationProgress treeBuildProgress;
if ( allScanUpdates.stream().allMatch( part -> part.mergeStarted ) )
{
long entryCount = allScanUpdates.stream().mapToLong( part -> part.count ).sum() + externalUpdates.count();
treeBuildProgress = PopulationProgress.single( numberOfAppliedScanUpdates + numberOfAppliedExternalUpdates, entryCount );
}
else
{
treeBuildProgress = PopulationProgress.NONE;
}
builder.add( treeBuildProgress, 2 );
return builder.build();
}
/**
* Keeps track of a {@link BlockStorage} instance as well as monitoring some aspects of it to be able to provide a fairly accurate
* progress report from {@link BlockBasedIndexPopulator#progress(PopulationProgress)}.
*/
private class ThreadLocalBlockStorage extends BlockStorage.Monitor.Delegate
{
private final BlockStorage<KEY,VALUE> blockStorage;
private volatile long count;
private volatile boolean mergeStarted;
private volatile long totalEntriesToMerge;
private volatile long entriesMerged;
ThreadLocalBlockStorage( int id ) throws IOException
{
super( blockStorageMonitor );
File blockFile = new File( storeFile.getParentFile(), storeFile.getName() + ".scan-" + id );
this.blockStorage = new BlockStorage<>( layout, bufferFactory, fileSystem, blockFile, this, blockSize );
}
@Override
public void mergeStarted( long entryCount, long totalEntriesToWriteDuringMerge )
{
super.mergeStarted( entryCount, totalEntriesToWriteDuringMerge );
this.count = entryCount;
this.totalEntriesToMerge = totalEntriesToWriteDuringMerge;
this.mergeStarted = true;
}
@Override
public void entriesMerged( int entries )
{
super.entriesMerged( entries );
entriesMerged += entries;
}
}
private static class CloseCancellation implements BlockStorage.Cancellation
{
private volatile boolean cancelled;
void setCancel()
{
this.cancelled = true;
}
@Override
public boolean cancelled()
{
return cancelled;
}
}
}