StephanEwen 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_r298111597
########## File path: flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/BufferReaderWriterUtil.java ########## @@ -0,0 +1,227 @@ +/* + * 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.runtime.io.network.buffer.FreeingBufferRecycler; +import org.apache.flink.runtime.io.network.buffer.NetworkBuffer; + +import javax.annotation.Nullable; + +import java.io.IOException; +import java.nio.BufferUnderflowException; +import java.nio.ByteBuffer; +import java.nio.ByteOrder; +import java.nio.channels.FileChannel; + +/** + * Putting and getting of a sequence of buffers to/from a FileChannel or a ByteBuffer. + * This class handles the headers, length encoding, memory slicing. + * + * <p>The encoding is the same across FileChannel and ByteBuffer, so this class can + * write to a file and read from the byte buffer that results from mapping this file to memory. + */ +final class BufferReaderWriterUtil { + + static final int HEADER_LENGTH = 8; + + static final int HEADER_VALUE_IS_BUFFER = 0; + + static final int HEADER_VALUE_IS_EVENT = 1; + + // ------------------------------------------------------------------------ + // ByteBuffer read / write + // ------------------------------------------------------------------------ + + static boolean writeBuffer(Buffer buffer, ByteBuffer memory) { + final int bufferSize = buffer.getSize(); + + if (memory.remaining() < bufferSize + HEADER_LENGTH) { + return false; + } + + memory.putInt(buffer.isBuffer() ? HEADER_VALUE_IS_BUFFER : HEADER_VALUE_IS_EVENT); + memory.putInt(bufferSize); + memory.put(buffer.getNioBufferReadable()); + return true; + } + + @Nullable + static Buffer sliceNextBuffer(ByteBuffer memory) { + final int remaining = memory.remaining(); + + // we only check the correct case where data is exhausted + // all other cases can only occur if our write logic is wrong and will already throw + // buffer underflow exceptions which will cause the read to fail. + if (remaining == 0) { + return null; + } + + final int header = memory.getInt(); + final int size = memory.getInt(); + + memory.limit(memory.position() + size); + ByteBuffer buf = memory.slice(); + memory.position(memory.limit()); + memory.limit(memory.capacity()); + + MemorySegment memorySegment = MemorySegmentFactory.wrapOffHeapMemory(buf); + + return bufferFromMemorySegment( + memorySegment, + FreeingBufferRecycler.INSTANCE, + size, + header == HEADER_VALUE_IS_EVENT); + } + + // ------------------------------------------------------------------------ + // ByteChannel read / write + // ------------------------------------------------------------------------ + + static long writeToByteChannel( + FileChannel channel, + Buffer buffer, + ByteBuffer[] arrayWithHeaderBuffer) throws IOException { + + final ByteBuffer headerBuffer = arrayWithHeaderBuffer[0]; + headerBuffer.clear(); + headerBuffer.putInt(buffer.isBuffer() ? HEADER_VALUE_IS_BUFFER : HEADER_VALUE_IS_EVENT); + headerBuffer.putInt(buffer.getSize()); + headerBuffer.flip(); + + arrayWithHeaderBuffer[1] = buffer.getNioBufferReadable(); + + return channel.write(arrayWithHeaderBuffer); Review comment: I was looking into this as well while writing. I think I found the docs saying that the file channel implementation does guarantee this, but I can double check and add a comment. ---------------------------------------------------------------- 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: us...@infra.apache.org With regards, Apache Git Services
