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Merged
merged 3 commits into from
Aug 18, 2021
Merged

Do not checksum on LZ4 compress #76666

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f3381ec
Do not checksum on LZ4 compress
Tim-Brooks Aug 18, 2021
3ad7b2e
Typo
Tim-Brooks Aug 18, 2021
f6eaa3d
Merge remote-tracking branch 'upstream/master' into no_checksum
Tim-Brooks Aug 18, 2021
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32 changes: 2 additions & 30 deletions server/src/main/java/org/elasticsearch/transport/Lz4TransportDecompressor.java
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Original file line number Diff line number Diff line change
Expand Up @@ -38,7 +38,6 @@
import java.io.IOException;
import java.util.ArrayDeque;
import java.util.Locale;
import java.util.zip.Checksum;

/**
* This file is forked from the https://netty.io project. In particular it forks the following file
Expand Down Expand Up @@ -100,11 +99,6 @@ private enum State {
*/
private LZ4FastDecompressor decompressor;

/**
* Underlying checksum calculator in use.
*/
private Checksum checksum;

/**
* Type of current block.
*/
Expand All @@ -120,11 +114,6 @@ private enum State {
*/
private int decompressedLength;

/**
* Checksum value of current incoming block.
*/
private int currentChecksum;

private final PageCacheRecycler recycler;
private final ArrayDeque<Recycler.V<byte[]>> pages;
private int pageOffset = PageCacheRecycler.BYTE_PAGE_SIZE;
Expand All @@ -134,7 +123,6 @@ public Lz4TransportDecompressor(PageCacheRecycler recycler) {
this.decompressor = LZ4Factory.safeInstance().fastDecompressor();
this.recycler = recycler;
this.pages = new ArrayDeque<>(4);
this.checksum = null;
}

@Override
Expand Down Expand Up @@ -232,23 +220,19 @@ private int decodeBlock(BytesReference reference) throws IOException {
compressedLength, decompressedLength));
}

int currentChecksum = Integer.reverseBytes(in.readInt());
// Read int where checksum would normally be written
in.readInt();
bytesConsumed += HEADER_LENGTH;

if (decompressedLength == 0) {
if (currentChecksum != 0) {
throw new IllegalStateException("stream corrupted: checksum error");
}
currentState = State.FINISHED;
decompressor = null;
checksum = null;
break;
}

this.blockType = blockType;
this.compressedLength = compressedLength;
this.decompressedLength = decompressedLength;
this.currentChecksum = currentChecksum;
}

currentState = State.DECOMPRESS_DATA;
Expand All @@ -258,7 +242,6 @@ private int decodeBlock(BytesReference reference) throws IOException {
break;
}

final Checksum checksum = this.checksum;
byte[] decompressed = getThreadLocalBuffer(DECOMPRESSED, decompressedLength);

try {
Expand Down Expand Up @@ -292,17 +275,6 @@ private int decodeBlock(BytesReference reference) throws IOException {
// Skip inbound bytes after we processed them.
bytesConsumed += compressedLength;

if (checksum != null) {
checksum.reset();
checksum.update(decompressed, 0, decompressedLength);
final int checksumResult = (int) checksum.getValue();
if (checksumResult != currentChecksum) {
throw new IllegalStateException(String.format(Locale.ROOT,
"stream corrupted: mismatching checksum: %d (expected: %d)",
checksumResult, currentChecksum));
}
}

int bytesToCopy = decompressedLength;
int uncompressedOffset = 0;
while (bytesToCopy > 0) {
Expand Down
75 changes: 11 additions & 64 deletions server/src/main/java/org/elasticsearch/transport/ReuseBuffersLZ4BlockOutputStream.java
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Original file line number Diff line number Diff line change
Expand Up @@ -23,21 +23,17 @@

package org.elasticsearch.transport;

import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.zip.Checksum;

import net.jpountz.lz4.LZ4BlockInputStream;
import net.jpountz.lz4.LZ4Compressor;
import net.jpountz.lz4.LZ4Factory;
import net.jpountz.lz4.LZ4FrameOutputStream;
import net.jpountz.util.SafeUtils;
import net.jpountz.xxhash.StreamingXXHash32;
import net.jpountz.xxhash.XXHashFactory;

import org.apache.lucene.util.BytesRef;

import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;

/**
* This file is forked from https://github.com/lz4/lz4-java. In particular it forks the following file
* net.jpountz.lz4.LZ4BlockOutputStream.
Expand All @@ -46,6 +42,8 @@
* the need to allocate two new byte arrays everytime a new stream is created. For the Elasticsearch use case,
* a single thread should fully compress the stream in one go to avoid memory corruption.
*
* Additionally, it does not checksum (or write a check) for the data compressed. We do not read the checksum
* when decompressing in Elasticsearch.
*
* Streaming LZ4 (not compatible with the LZ4 Frame format).
* This class compresses data into fixed-size blocks of compressed data.
Expand Down Expand Up @@ -116,7 +114,6 @@ private static int compressionLevel(int blockSize) {
private final int blockSize;
private final int compressionLevel;
private final LZ4Compressor compressor;
private final Checksum checksum;
private final ArrayBox arrayBox;
private final byte[] buffer;
private final byte[] compressedBuffer;
Expand All @@ -134,71 +131,23 @@ private static int compressionLevel(int blockSize) {
* must be &gt;= 64 and &lt;= 32 M
* @param compressor the {@link LZ4Compressor} instance to use to compress
* data
* @param checksum the {@link Checksum} instance to use to check data for
* integrity.
* @param syncFlush true if pending data should also be flushed on {@link #flush()}
*/
public ReuseBuffersLZ4BlockOutputStream(OutputStream out, int blockSize, LZ4Compressor compressor, Checksum checksum,
boolean syncFlush) {
public ReuseBuffersLZ4BlockOutputStream(OutputStream out, int blockSize, LZ4Compressor compressor) {
super(out);
this.blockSize = blockSize;
this.compressor = compressor;
this.checksum = checksum;
this.compressionLevel = compressionLevel(blockSize);
final int compressedBlockSize = HEADER_LENGTH + compressor.maxCompressedLength(blockSize);
this.arrayBox = ARRAY_BOX.get();
arrayBox.markOwnership(blockSize, compressedBlockSize);
this.buffer = arrayBox.uncompressed;
this.compressedBuffer = arrayBox.compressed;
this.syncFlush = syncFlush;
this.syncFlush = false;
o = 0;
finished = false;
System.arraycopy(MAGIC, 0, compressedBuffer, 0, MAGIC_LENGTH);
}

/**
* Creates a new instance which checks stream integrity using
* {@link StreamingXXHash32} and doesn't sync flush.
*
* @param out the {@link OutputStream} to feed
* @param blockSize the maximum number of bytes to try to compress at once,
* must be &gt;= 64 and &lt;= 32 M
* @param compressor the {@link LZ4Compressor} instance to use to compress
* data
*
* @see #ReuseBuffersLZ4BlockOutputStream(OutputStream, int, LZ4Compressor, Checksum, boolean)
* @see StreamingXXHash32#asChecksum()
*/
public ReuseBuffersLZ4BlockOutputStream(OutputStream out, int blockSize, LZ4Compressor compressor) {
this(out, blockSize, compressor, XXHashFactory.fastestInstance().newStreamingHash32(DEFAULT_SEED).asChecksum(), false);
}

/**
* Creates a new instance which compresses with the standard LZ4 compression
* algorithm.
*
* @param out the {@link OutputStream} to feed
* @param blockSize the maximum number of bytes to try to compress at once,
* must be &gt;= 64 and &lt;= 32 M
*
* @see #ReuseBuffersLZ4BlockOutputStream(OutputStream, int, LZ4Compressor)
* @see LZ4Factory#fastCompressor()
*/
public ReuseBuffersLZ4BlockOutputStream(OutputStream out, int blockSize) {
this(out, blockSize, LZ4Factory.fastestInstance().fastCompressor());
}

/**
* Creates a new instance which compresses into blocks of 64 KB.
*
* @param out the {@link OutputStream} to feed
*
* @see #ReuseBuffersLZ4BlockOutputStream(OutputStream, int)
*/
public ReuseBuffersLZ4BlockOutputStream(OutputStream out) {
this(out, 1 << 16);
}

private void ensureNotFinished() {
if (finished) {
throw new IllegalStateException("This stream is already closed");
Expand Down Expand Up @@ -256,9 +205,6 @@ private void flushBufferedData() throws IOException {
if (o == 0) {
return;
}
checksum.reset();
checksum.update(buffer, 0, o);
final int check = (int) checksum.getValue();
int compressedLength = compressor.compress(buffer, 0, o, compressedBuffer, HEADER_LENGTH);
final int compressMethod;
if (compressedLength >= o) {
Expand All @@ -272,7 +218,8 @@ private void flushBufferedData() throws IOException {
compressedBuffer[MAGIC_LENGTH] = (byte) (compressMethod | compressionLevel);
writeIntLE(compressedLength, compressedBuffer, MAGIC_LENGTH + 1);
writeIntLE(o, compressedBuffer, MAGIC_LENGTH + 5);
writeIntLE(check, compressedBuffer, MAGIC_LENGTH + 9);
// Write 0 for checksum. We do not read it on decompress.
writeIntLE(0, compressedBuffer, MAGIC_LENGTH + 9);
assert MAGIC_LENGTH + 13 == HEADER_LENGTH;
out.write(compressedBuffer, 0, HEADER_LENGTH + compressedLength);
o = 0;
Expand Down Expand Up @@ -327,7 +274,7 @@ private static void writeIntLE(int i, byte[] buf, int off) {
@Override
public String toString() {
return getClass().getSimpleName() + "(out=" + out + ", blockSize=" + blockSize
+ ", compressor=" + compressor + ", checksum=" + checksum + ")";
+ ", compressor=" + compressor + ")";
}

}
Expand Down