Better support for partial buffer reads/writes in translog infrastructure #6576
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,106 @@ | ||
| /* | ||
| * 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.common.io; | ||
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| import org.jboss.netty.buffer.ChannelBuffer; | ||
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| import java.io.EOFException; | ||
| import java.io.IOException; | ||
| import java.nio.ByteBuffer; | ||
| import java.nio.channels.FileChannel; | ||
| import java.nio.channels.GatheringByteChannel; | ||
| import java.nio.channels.WritableByteChannel; | ||
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| public abstract class Channels { | ||
| /** | ||
| * The maximum chunk size for reads in bytes | ||
| */ | ||
| private static final int READ_CHUNK_SIZE = 16384; | ||
| /** | ||
| * The maximum chunk size for writes in bytes | ||
| */ | ||
| private static final int WRITE_CHUNK_SIZE = 8192; | ||
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| /** | ||
| * read <i>length</i> bytes from <i>position</i> of a file channel | ||
| */ | ||
| public static byte[] readFromFileChannel(FileChannel channel, long position, int length) throws IOException { | ||
| byte[] res = new byte[length]; | ||
| readFromFileChannel(channel, position, res, 0, length); | ||
| return res; | ||
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| } | ||
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| /** | ||
| * read <i>length</i> bytes from <i>position</i> of a file channel | ||
| * | ||
| * @param channel channel to read from | ||
| * @param channelPosition position to read from | ||
| * @param dest destination byte array to put data in | ||
| * @param destOffset offset in dest to read into | ||
| * @param length number of bytes to read | ||
| */ | ||
| public static void readFromFileChannel(FileChannel channel, long channelPosition, byte[] dest, int destOffset, int length) throws IOException { | ||
| ByteBuffer buffer = ByteBuffer.wrap(dest, destOffset, length); | ||
| while (length > 0) { | ||
| final int toRead = Math.min(READ_CHUNK_SIZE, length); | ||
| buffer.limit(buffer.position() + toRead); | ||
| assert buffer.remaining() == toRead; | ||
| final int i = channel.read(buffer, channelPosition); | ||
| if (i < 0) { // be defensive here, even though we checked before hand, something could have changed | ||
| throw new EOFException("read past EOF. pos [" + channelPosition + "] chunkLen: [" + toRead + "] end: [" + channel.size() + "]"); | ||
| } | ||
| assert i > 0 : "FileChannel.read with non zero-length bb.remaining() must always read at least one byte (FileChannel is in blocking mode, see spec of ReadableByteChannel)"; | ||
| channelPosition += i; | ||
| length -= i; | ||
| } | ||
| assert length == 0; | ||
|
There was a problem hiding this comment. if you debug this you really wanna know the length.... maybe add a msg to it? |
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| } | ||
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| public static void writeToChannel(ChannelBuffer source, int sourceIndex, int length, GatheringByteChannel channel) throws IOException { | ||
| while (length > 0) { | ||
| int written = source.getBytes(sourceIndex, channel, length); | ||
| sourceIndex += written; | ||
| length -= written; | ||
| } | ||
| assert length == 0; | ||
| } | ||
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| public static void writeToChannel(byte[] source, int offset, int length, WritableByteChannel channel) throws IOException { | ||
| int toWrite = Math.min(length, WRITE_CHUNK_SIZE); | ||
| ByteBuffer buffer = ByteBuffer.wrap(source, offset, toWrite); | ||
| int written = channel.write(buffer); | ||
| length -= written; | ||
| while (length > 0) { | ||
| toWrite = Math.min(length, WRITE_CHUNK_SIZE); | ||
| buffer.limit(buffer.position() + toWrite); | ||
| written = channel.write(buffer); | ||
| length -= written; | ||
| } | ||
| assert length == 0; | ||
| } | ||
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| public static void writeToChannel(ByteBuffer byteBuffer, WritableByteChannel channel) throws IOException { | ||
| do { | ||
| channel.write(byteBuffer); | ||
|
There was a problem hiding this comment. I am not sure, but I think we need to chunk this write as well, or the JVM could allocate a big threadlocal buffer that hangs around... There was a problem hiding this comment. I agree. If the ByteBuffer is not a direct buffer, we should chunk. Maybe check if it is direct and chunk only then. |
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| } | ||
| while (byteBuffer.position() != byteBuffer.limit()); | ||
| } | ||
| } | ||
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Can we have a real unittest for this class? I mean it's tested well but I'd love to have a dedicated test for that really hammers it.
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can we make this class final with a default private ctor?
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final I get. Wondering why the default private ctor?
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Ah - I get it :) final to prevent extending, private ctor to replace the abstract. Coming up.