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Move caching of the size of a directory to
StoreDirectory. (#30581)
In spite of the existing caching, I have seen a number of nodes hot threads where one thread had been spending all its cpu on computing the size of a directory. I am proposing to move the computation of the size of the directory to `StoreDirectory` in order to skip recomputing the size of the directory if no changes have been made. This should help with users that have read-only indices, which is very common for time-based indices.
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183 changes: 183 additions & 0 deletions
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server/src/main/java/org/elasticsearch/index/store/ByteSizeCachingDirectory.java
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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. | ||
| */ | ||
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| package org.elasticsearch.index.store; | ||
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| 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; | ||
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| import java.io.FileNotFoundException; | ||
| import java.io.IOException; | ||
| import java.io.UncheckedIOException; | ||
| import java.nio.file.AccessDeniedException; | ||
| import java.nio.file.NoSuchFileException; | ||
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| final class ByteSizeCachingDirectory extends FilterDirectory { | ||
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| private static class SizeAndModCount { | ||
| final long size; | ||
| final long modCount; | ||
| final boolean pendingWrite; | ||
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| SizeAndModCount(long length, long modCount, boolean pendingWrite) { | ||
| this.size = length; | ||
| this.modCount = modCount; | ||
| this.pendingWrite = pendingWrite; | ||
| } | ||
| } | ||
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| 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; | ||
| } | ||
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| private final SingleObjectCache<SizeAndModCount> size; | ||
| // Both these variables need to be accessed under `this` lock. | ||
| private long modCount = 0; | ||
| private long numOpenOutputs = 0; | ||
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| ByteSizeCachingDirectory(Directory in, TimeValue refreshInterval) { | ||
| super(in); | ||
| size = new SingleObjectCache<SizeAndModCount>(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); | ||
| } | ||
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| @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; | ||
| } | ||
| } | ||
| }; | ||
| } | ||
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| /** 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(); | ||
| } | ||
| } | ||
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| @Override | ||
| public IndexOutput createOutput(String name, IOContext context) throws IOException { | ||
| return wrapIndexOutput(super.createOutput(name, context)); | ||
| } | ||
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| @Override | ||
| public IndexOutput createTempOutput(String prefix, String suffix, IOContext context) throws IOException { | ||
| return wrapIndexOutput(super.createTempOutput(prefix, suffix, context)); | ||
| } | ||
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| 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); | ||
| } | ||
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| @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); | ||
| } | ||
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| @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 (this) { | ||
| numOpenOutputs--; | ||
| modCount++; | ||
| } | ||
| } | ||
| } | ||
| }; | ||
| } | ||
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| @Override | ||
| public void deleteFile(String name) throws IOException { | ||
| try { | ||
| super.deleteFile(name); | ||
| } finally { | ||
| synchronized (this) { | ||
| modCount++; | ||
| } | ||
| } | ||
| } | ||
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| } |
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