wsry commented on a change in pull request #8880: [FLINK-12986] [network] Fix instability of BoundedBlockingSubpartition under memory pressure. URL: https://github.com/apache/flink/pull/8880#discussion_r298059529
########## File path: flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/FileChannelBoundedData.java ########## @@ -0,0 +1,160 @@ +/* + * 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.flink.runtime.io.network.partition; + +import org.apache.flink.core.memory.MemorySegment; +import org.apache.flink.core.memory.MemorySegmentFactory; +import org.apache.flink.runtime.io.network.buffer.Buffer; +import org.apache.flink.runtime.io.network.buffer.BufferRecycler; +import org.apache.flink.util.IOUtils; + +import javax.annotation.Nullable; + +import java.io.IOException; +import java.nio.ByteBuffer; +import java.nio.channels.FileChannel; +import java.nio.file.Files; +import java.nio.file.Path; +import java.nio.file.StandardOpenOption; +import java.util.ArrayDeque; + +import static org.apache.flink.util.Preconditions.checkNotNull; +import static org.apache.flink.util.Preconditions.checkState; + +/** + * An implementation of {@link BoundedData} that writes directly into a File Channel. + * The readers are simple file channel readers using a simple dedicated buffer pool. + */ +final class FileChannelBoundedData implements BoundedData { + + private final Path filePath; + + private final FileChannel fileChannel; + + private final ByteBuffer[] headerAndBufferArray; + + private long size; + + private final int memorySegmentSize; + + FileChannelBoundedData( + Path filePath, + FileChannel fileChannel, + int memorySegmentSize) { + + this.filePath = checkNotNull(filePath); + this.fileChannel = checkNotNull(fileChannel); + this.memorySegmentSize = memorySegmentSize; + this.headerAndBufferArray = BufferReaderWriterUtil.allocatedWriteBufferArray(); + } + + @Override + public void writeBuffer(Buffer buffer) throws IOException { + size += BufferReaderWriterUtil.writeToByteChannel(fileChannel, buffer, headerAndBufferArray); + } + + @Override + public void finishWrite() throws IOException { + fileChannel.close(); + } + + @Override + public Reader createReader() throws IOException { + checkState(!fileChannel.isOpen()); + + final FileChannel fc = FileChannel.open(filePath, StandardOpenOption.READ); + return new FileBufferReader(fc, memorySegmentSize); + } + + @Override + public long getSize() { + return size; + } + + @Override + public void close() throws IOException { + IOUtils.closeQuietly(fileChannel); + Files.delete(filePath); + } + + // ------------------------------------------------------------------------ + + public static FileChannelBoundedData create(Path filePath, int memorySegmentSize) throws IOException { + final FileChannel fileChannel = FileChannel.open( + filePath, StandardOpenOption.CREATE_NEW, StandardOpenOption.WRITE); + + return new FileChannelBoundedData( + filePath, + fileChannel, + memorySegmentSize); + } + + // ------------------------------------------------------------------------ + + static final class FileBufferReader implements BoundedData.Reader, BufferRecycler { + + private static final int NUM_BUFFERS = 2; + + private final FileChannel fileChannel; + + private final ByteBuffer headerBuffer; + + private final ArrayDeque<MemorySegment> buffers; + + FileBufferReader(FileChannel fileChannel, int bufferSize) { + this.fileChannel = checkNotNull(fileChannel); + this.headerBuffer = BufferReaderWriterUtil.allocatedHeaderBuffer(); + this.buffers = new ArrayDeque<>(NUM_BUFFERS); + + for (int i = 0; i < NUM_BUFFERS; i++) { + buffers.addLast(MemorySegmentFactory.allocateUnpooledOffHeapMemory(bufferSize, null)); + } + } + + @Nullable + @Override + public Buffer nextBuffer() throws IOException { + final MemorySegment memory = buffers.pollFirst(); + + if (memory != null) { + final Buffer next = BufferReaderWriterUtil.readFromByteChannel(fileChannel, headerBuffer, memory, this); + if (next != null) { + return next; + } + else { + recycle(memory); + return null; + } + } + + throw new IOException("Bug in BoundedBlockingSubpartition with FILE data: " + Review comment: Though, theoretically, two read buffers is enough. But there could be still problems, because the writeAndFlush method of netty channel dose not work synchronously and the reader can be scheduled not only when the buffer of the same reader is sent out but also when the downstream adding credit or when buffers of other readers multiplex the same channel are sent out. So it is unsafe to make the assumption that when the reader is scheduled there must be a buffer for reading ahead. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services
