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*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*
*/
package org.apache.cassandra.cache;
import java.nio.ByteBuffer;
import java.util.concurrent.atomic.AtomicInteger;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Throwables;
import com.google.common.collect.Iterables;
import com.google.common.util.concurrent.MoreExecutors;
import com.github.benmanes.caffeine.cache.*;
import com.codahale.metrics.Timer;
import org.apache.cassandra.config.DatabaseDescriptor;
import org.apache.cassandra.io.sstable.CorruptSSTableException;
import org.apache.cassandra.io.util.*;
import org.apache.cassandra.metrics.CacheMissMetrics;
import org.apache.cassandra.utils.memory.BufferPool;
public class ChunkCache
implements CacheLoader<ChunkCache.Key, ChunkCache.Buffer>, RemovalListener<ChunkCache.Key, ChunkCache.Buffer>, CacheSize
{
public static final int RESERVED_POOL_SPACE_IN_MB = 32;
public static final long cacheSize = 1024L * 1024L * Math.max(0, DatabaseDescriptor.getFileCacheSizeInMB() - RESERVED_POOL_SPACE_IN_MB);
private static boolean enabled = cacheSize > 0;
public static final ChunkCache instance = enabled ? new ChunkCache() : null;
private final LoadingCache<Key, Buffer> cache;
public final CacheMissMetrics metrics;
static class Key
{
final ChunkReader file;
final String path;
final long position;
public Key(ChunkReader file, long position)
{
super();
this.file = file;
this.position = position;
this.path = file.channel().filePath();
}
public int hashCode()
{
final int prime = 31;
int result = 1;
result = prime * result + path.hashCode();
result = prime * result + file.getClass().hashCode();
result = prime * result + Long.hashCode(position);
return result;
}
public boolean equals(Object obj)
{
if (this == obj)
return true;
if (obj == null)
return false;
Key other = (Key) obj;
return (position == other.position)
&& file.getClass() == other.file.getClass()
&& path.equals(other.path);
}
}
static class Buffer implements Rebufferer.BufferHolder
{
private final ByteBuffer buffer;
private final long offset;
private final AtomicInteger references;
public Buffer(ByteBuffer buffer, long offset)
{
this.buffer = buffer;
this.offset = offset;
references = new AtomicInteger(1); // start referenced.
}
Buffer reference()
{
int refCount;
do
{
refCount = references.get();
if (refCount == 0)
// Buffer was released before we managed to reference it.
return null;
} while (!references.compareAndSet(refCount, refCount + 1));
return this;
}
@Override
public ByteBuffer buffer()
{
assert references.get() > 0;
return buffer.duplicate();
}
@Override
public long offset()
{
return offset;
}
@Override
public void release()
{
if (references.decrementAndGet() == 0)
BufferPool.put(buffer);
}
}
public ChunkCache()
{
cache = Caffeine.newBuilder()
.maximumWeight(cacheSize)
.executor(MoreExecutors.directExecutor())
.weigher((key, buffer) -> ((Buffer) buffer).buffer.capacity())
.removalListener(this)
.build(this);
metrics = new CacheMissMetrics("ChunkCache", this);
}
@Override
public Buffer load(Key key) throws Exception
{
ChunkReader rebufferer = key.file;
metrics.misses.mark();
try (Timer.Context ctx = metrics.missLatency.time())
{
ByteBuffer buffer = BufferPool.get(key.file.chunkSize(), key.file.preferredBufferType());
assert buffer != null;
rebufferer.readChunk(key.position, buffer);
return new Buffer(buffer, key.position);
}
}
@Override
public void onRemoval(Key key, Buffer buffer, RemovalCause cause)
{
buffer.release();
}
public void close()
{
cache.invalidateAll();
}
public RebuffererFactory wrap(ChunkReader file)
{
return new CachingRebufferer(file);
}
public static RebuffererFactory maybeWrap(ChunkReader file)
{
if (!enabled)
return file;
return instance.wrap(file);
}
public void invalidatePosition(FileHandle dfile, long position)
{
if (!(dfile.rebuffererFactory() instanceof CachingRebufferer))
return;
((CachingRebufferer) dfile.rebuffererFactory()).invalidate(position);
}
public void invalidateFile(String fileName)
{
cache.invalidateAll(Iterables.filter(cache.asMap().keySet(), x -> x.path.equals(fileName)));
}
@VisibleForTesting
public void enable(boolean enabled)
{
ChunkCache.enabled = enabled;
cache.invalidateAll();
metrics.reset();
}
// TODO: Invalidate caches for obsoleted/MOVED_START tables?
/**
* Rebufferer providing cached chunks where data is obtained from the specified ChunkReader.
* Thread-safe. One instance per SegmentedFile, created by ChunkCache.maybeWrap if the cache is enabled.
*/
class CachingRebufferer implements Rebufferer, RebuffererFactory
{
private final ChunkReader source;
final long alignmentMask;
public CachingRebufferer(ChunkReader file)
{
source = file;
int chunkSize = file.chunkSize();
assert Integer.bitCount(chunkSize) == 1; // Must be power of two
alignmentMask = -chunkSize;
}
@Override
public Buffer rebuffer(long position)
{
try
{
metrics.requests.mark();
long pageAlignedPos = position & alignmentMask;
Buffer buf;
do
buf = cache.get(new Key(source, pageAlignedPos)).reference();
while (buf == null);
return buf;
}
catch (Throwable t)
{
Throwables.propagateIfInstanceOf(t.getCause(), CorruptSSTableException.class);
throw Throwables.propagate(t);
}
}
public void invalidate(long position)
{
long pageAlignedPos = position & alignmentMask;
cache.invalidate(new Key(source, pageAlignedPos));
}
@Override
public Rebufferer instantiateRebufferer()
{
return this;
}
@Override
public void close()
{
source.close();
}
@Override
public void closeReader()
{
// Instance is shared among readers. Nothing to release.
}
@Override
public ChannelProxy channel()
{
return source.channel();
}
@Override
public long fileLength()
{
return source.fileLength();
}
@Override
public double getCrcCheckChance()
{
return source.getCrcCheckChance();
}
@Override
public String toString()
{
return "CachingRebufferer:" + source;
}
}
@Override
public long capacity()
{
return cacheSize;
}
@Override
public void setCapacity(long capacity)
{
throw new UnsupportedOperationException("Chunk cache size cannot be changed.");
}
@Override
public int size()
{
return cache.asMap().size();
}
@Override
public long weightedSize()
{
return cache.policy().eviction()
.map(policy -> policy.weightedSize().orElseGet(cache::estimatedSize))
.orElseGet(cache::estimatedSize);
}
}