wsry commented on a change in pull request #13924: URL: https://github.com/apache/flink/pull/13924#discussion_r602130482
########## File path: flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/SortMergeResultPartitionReadScheduler.java ########## @@ -0,0 +1,395 @@ +/* + * 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.annotation.VisibleForTesting; +import org.apache.flink.core.memory.MemorySegment; +import org.apache.flink.runtime.io.disk.BatchShuffleReadBufferPool; +import org.apache.flink.runtime.io.network.buffer.BufferRecycler; +import org.apache.flink.runtime.util.FatalExitExceptionHandler; +import org.apache.flink.util.IOUtils; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import javax.annotation.concurrent.GuardedBy; + +import java.io.IOException; +import java.nio.channels.FileChannel; +import java.nio.file.Path; +import java.nio.file.StandardOpenOption; +import java.util.ArrayDeque; +import java.util.ArrayList; +import java.util.Collection; +import java.util.Collections; +import java.util.HashSet; +import java.util.List; +import java.util.PriorityQueue; +import java.util.Queue; +import java.util.Set; +import java.util.concurrent.CompletableFuture; +import java.util.concurrent.Executor; +import java.util.concurrent.TimeoutException; + +import static org.apache.flink.util.Preconditions.checkNotNull; +import static org.apache.flink.util.Preconditions.checkState; + +/** + * Data reader for {@link SortMergeResultPartition} which can read data for all downstream tasks + * consuming the corresponding {@link SortMergeResultPartition}. It always tries to read shuffle + * data in order of file offset, which maximums the sequential read so can improve the blocking + * shuffle performance. + */ +class SortMergeResultPartitionReadScheduler implements Runnable, BufferRecycler { + + private static final Logger LOG = + LoggerFactory.getLogger(SortMergeResultPartitionReadScheduler.class); + + private final FatalExitExceptionHandler fatalErrorHandler = new FatalExitExceptionHandler(); + + /** Lock used to synchronize multi-thread access to thread-unsafe fields. */ + private final Object lock; + + /** + * A {@link CompletableFuture} to be completed when this read scheduler including all resources + * is released. + */ + private final CompletableFuture<?> releaseFuture = new CompletableFuture<>(); + + /** Buffer pool from which to allocate buffers for shuffle data reading. */ + private final BatchShuffleReadBufferPool bufferPool; + + /** Executor to run the shuffle data reading task. */ + private final Executor ioExecutor; + + /** Maximum number of buffers can be allocated by this partition reader. */ + private final int maxRequestedBuffers; + + /** All failed subpartition readers to be released. */ + @GuardedBy("lock") + private final Set<SortMergeSubpartitionReader> failedReaders = new HashSet<>(); + + /** All readers waiting to read data of different subpartitions. */ + @GuardedBy("lock") + private final Set<SortMergeSubpartitionReader> allReaders = new HashSet<>(); + + /** File channel shared by all subpartitions to read data from. */ + @GuardedBy("lock") + private FileChannel dataFileChannel; + + /** File channel shared by all subpartitions to read index from. */ + @GuardedBy("lock") + private FileChannel indexFileChannel; + + /** Number of buffers already allocated and still not recycled by this partition reader. */ + @GuardedBy("lock") + private int numRequestedBuffers; + + /** + * Whether the data reading task is currently running or not. This flag is used when trying to + * submit the data reading task. + */ + @GuardedBy("lock") + private boolean isRunning; + + /** Whether this reader has been released or not. */ + @GuardedBy("lock") + private boolean isReleased; + + SortMergeResultPartitionReadScheduler( + BatchShuffleReadBufferPool bufferPool, Executor ioExecutor, Object lock) { + this.lock = checkNotNull(lock); + this.bufferPool = checkNotNull(bufferPool); + this.ioExecutor = checkNotNull(ioExecutor); + // one partition reader can consume at most 32M (the expected buffers per request is 8M) + // buffers for data read. Currently, it is only an empirical value can not be configured + this.maxRequestedBuffers = Math.max(1, 4 * bufferPool.getNumBuffersPerRequest()); + + // initialize the buffer pool eagerly to avoid reporting errors like OOM too late + bufferPool.initialize(); + } + + @Override + public synchronized void run() { + Queue<SortMergeSubpartitionReader> availableReaders = getAvailableReaders(); + + Queue<MemorySegment> buffers = allocateBuffers(availableReaders); + int numBuffersAllocated = buffers.size(); + + Set<SortMergeSubpartitionReader> finishedReaders = readData(availableReaders, buffers); + + int numBuffersRead = numBuffersAllocated - buffers.size(); + releaseBuffers(buffers); + + removeFinishedAndFailedReaders(numBuffersRead, finishedReaders); + } + + private Queue<MemorySegment> allocateBuffers( + Queue<SortMergeSubpartitionReader> availableReaders) { + if (availableReaders.isEmpty()) { + return new ArrayDeque<>(); + } + + try { + return new ArrayDeque<>(bufferPool.requestBuffers()); + } catch (Throwable throwable) { + // do not fail the pending subpartitions if the TimeoutException occurs and we are + // currently holding buffers, otherwise, fail all pending subpartitions immediately + if (!(throwable instanceof TimeoutException) || numRequestedBuffers <= 0) { Review comment: I moved the timeout logic to this method and changed the logic here which is easier to understand now. -- This is an automated message from the Apache Git Service. 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