StephanEwen commented on a change in pull request #8290: [FLINK-12070] [network] Implement new bounded blocking subpartitions URL: https://github.com/apache/flink/pull/8290#discussion_r281145295
########## File path: flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/BoundedBlockingSubpartitionReader.java ########## @@ -0,0 +1,191 @@ +/* + * 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.runtime.io.network.buffer.Buffer; +import org.apache.flink.runtime.io.network.partition.ResultSubpartition.BufferAndBacklog; + +import javax.annotation.Nullable; + +import java.io.IOException; +import java.nio.ByteBuffer; +import java.util.Collections; +import java.util.Iterator; + +import static org.apache.flink.util.Preconditions.checkArgument; +import static org.apache.flink.util.Preconditions.checkNotNull; + +/** + * The reader (read view) of a BoundedBlockingSubpartition. + */ +class BoundedBlockingSubpartitionReader implements ResultSubpartitionView { + + /** The result subpartition that we read. */ + private final BoundedBlockingSubpartition parent; + + /** Further byte buffers, to handle cases where there is more data than fits into + * one mapped byte buffer (2GB = Integer.MAX_VALUE). */ + private final Iterator<ByteBuffer> furtherData; + + /** The reader/decoder to the memory mapped region with the data we currently read from. + * Max 2GB large. Further regions may be in the {@link #furtherData} field. + * Null once the reader empty or disposed.*/ + @Nullable + private BoundedBlockingSubpartitionMemory.Reader data; + + /** The next buffer (look ahead). Null once the data is depleted or reader is disposed. */ + @Nullable + private Buffer nextBuffer; + + /** The remaining number of data buffers (not events) in the result. */ + private int bufferBacklog; + + /** Flag whether this reader is released. Atomic, to avoid double release. */ + private boolean isReleased; + + /** + * Convenience constructor that takes a single buffer. + */ + BoundedBlockingSubpartitionReader( + BoundedBlockingSubpartition parent, + ByteBuffer data, + int numBuffers) throws IOException { + this(parent, Collections.singleton(data), numBuffers); + } + + /** + * The general constructor that takes a queue of buffers containing the data. + */ + BoundedBlockingSubpartitionReader( + BoundedBlockingSubpartition parent, + Iterable<ByteBuffer> data, + int numBuffers) throws IOException { + + checkArgument(numBuffers >= 0); + + this.parent = checkNotNull(parent); + this.bufferBacklog = numBuffers; + + this.furtherData = data.iterator(); + checkArgument(furtherData.hasNext()); + + this.data = new BoundedBlockingSubpartitionMemory.Reader(furtherData.next()); + this.nextBuffer = fillNextBuffer(); + } + + @Nullable + @Override + public BufferAndBacklog getNextBuffer() throws IOException { + final Buffer current = nextBuffer; // copy reference to stack + + if (current == null) { + // as per contract, we must return null when the reader is empty, + // but also in case the reader is disposed (rather than throwing an exception) + return null; + } + if (current.isBuffer()) { + bufferBacklog--; + } + + Buffer next = fillNextBuffer(); + nextBuffer = next; + + return new BufferAndBacklog( + current, + next != null, + bufferBacklog, + next != null && !next.isBuffer()); + } + + @Nullable + private Buffer fillNextBuffer() throws IOException { + // should only be null once empty or disposed, in which case this method + // should not be called any more + assert data != null; + + final Buffer next = data.sliceNextBuffer(); + if (next != null) { + return next; + } + + if (!furtherData.hasNext()) { + data = null; + return null; + } + + data = new BoundedBlockingSubpartitionMemory.Reader(furtherData.next()); + return fillNextBuffer(); + } + + @Override + public void notifyDataAvailable() { + throw new IllegalStateException("No data should become available on a blocking partition during consumption."); + } + + @Override + public void notifySubpartitionConsumed() throws IOException { + parent.onConsumedSubpartition(); + } + + @Override + public void releaseAllResources() throws IOException { + // mark released and prevent double release + if (isReleased) { + return; + } + isReleased = true; + + // nulling these fields means thet read method and will fail fast Review comment: yes ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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