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/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch 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.elasticsearch.index.store;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FilterDirectory;
import org.apache.lucene.store.IOContext;
import org.apache.lucene.store.IndexOutput;
import org.elasticsearch.common.lucene.store.FilterIndexOutput;
import org.elasticsearch.common.unit.TimeValue;
import org.elasticsearch.common.util.SingleObjectCache;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.nio.file.AccessDeniedException;
import java.nio.file.NoSuchFileException;
import java.util.Set;
final class ByteSizeCachingDirectory extends FilterDirectory {
private static class SizeAndModCount {
final long size;
final long modCount;
final boolean pendingWrite;
SizeAndModCount(long length, long modCount, boolean pendingWrite) {
this.size = length;
this.modCount = modCount;
this.pendingWrite = pendingWrite;
}
}
private static long estimateSizeInBytes(Directory directory) throws IOException {
long estimatedSize = 0;
String[] files = directory.listAll();
for (String file : files) {
try {
estimatedSize += directory.fileLength(file);
} catch (NoSuchFileException | FileNotFoundException | AccessDeniedException e) {
// ignore, the file is not there no more; on Windows, if one thread concurrently deletes a file while
// calling Files.size, you can also sometimes hit AccessDeniedException
}
}
return estimatedSize;
}
private final SingleObjectCache size;
// Both these variables need to be accessed under `this` lock.
private long modCount = 0;
private long numOpenOutputs = 0;
ByteSizeCachingDirectory(Directory in, TimeValue refreshInterval) {
super(in);
size = new SingleObjectCache(refreshInterval, new SizeAndModCount(0L, -1L, true)) {
@Override
protected SizeAndModCount refresh() {
// It is ok for the size of the directory to be more recent than
// the mod count, we would just recompute the size of the
// directory on the next call as well. However the opposite
// would be bad as we would potentially have a stale cache
// entry for a long time. So we fetch the values of modCount and
// numOpenOutputs BEFORE computing the size of the directory.
final long modCount;
final boolean pendingWrite;
synchronized(ByteSizeCachingDirectory.this) {
modCount = ByteSizeCachingDirectory.this.modCount;
pendingWrite = ByteSizeCachingDirectory.this.numOpenOutputs != 0;
}
final long size;
try {
// Compute this OUTSIDE of the lock
size = estimateSizeInBytes(getDelegate());
} catch (IOException e) {
throw new UncheckedIOException(e);
}
return new SizeAndModCount(size, modCount, pendingWrite);
}
@Override
protected boolean needsRefresh() {
if (super.needsRefresh() == false) {
// The size was computed recently, don't recompute
return false;
}
SizeAndModCount cached = getNoRefresh();
if (cached.pendingWrite) {
// The cached entry was generated while there were pending
// writes, so the size might be stale: recompute.
return true;
}
synchronized(ByteSizeCachingDirectory.this) {
// If there are pending writes or if new files have been
// written/deleted since last time: recompute
return numOpenOutputs != 0 || cached.modCount != modCount;
}
}
};
}
/** Return the cumulative size of all files in this directory. */
long estimateSizeInBytes() throws IOException {
try {
return size.getOrRefresh().size;
} catch (UncheckedIOException e) {
// we wrapped in the cache and unwrap here
throw e.getCause();
}
}
@Override
public IndexOutput createOutput(String name, IOContext context) throws IOException {
return wrapIndexOutput(super.createOutput(name, context));
}
@Override
public IndexOutput createTempOutput(String prefix, String suffix, IOContext context) throws IOException {
return wrapIndexOutput(super.createTempOutput(prefix, suffix, context));
}
private IndexOutput wrapIndexOutput(IndexOutput out) {
synchronized (this) {
numOpenOutputs++;
}
return new FilterIndexOutput(out.toString(), out) {
@Override
public void writeBytes(byte[] b, int length) throws IOException {
// Don't write to atomicXXX here since it might be called in
// tight loops and memory barriers are costly
super.writeBytes(b, length);
}
@Override
public void writeByte(byte b) throws IOException {
// Don't write to atomicXXX here since it might be called in
// tight loops and memory barriers are costly
super.writeByte(b);
}
@Override
public void close() throws IOException {
// Close might cause some data to be flushed from in-memory buffers, so
// increment the modification counter too.
try {
super.close();
} finally {
synchronized (ByteSizeCachingDirectory.this) {
numOpenOutputs--;
modCount++;
}
}
}
};
}
@Override
public void deleteFile(String name) throws IOException {
try {
super.deleteFile(name);
} finally {
synchronized (this) {
modCount++;
}
}
}
// temporary override until LUCENE-8735 is integrated
@Override
public Set getPendingDeletions() throws IOException {
return in.getPendingDeletions();
}
}