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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-8178) Introduce not threadsafe write only BufferBuilder
Date Tue, 12 Dec 2017 17:06:03 GMT

    [ https://issues.apache.org/jira/browse/FLINK-8178?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16287920#comment-16287920
] 

ASF GitHub Bot commented on FLINK-8178:
---------------------------------------

Github user NicoK commented on a diff in the pull request:

    https://github.com/apache/flink/pull/5105#discussion_r156418933
  
    --- Diff: flink-runtime/src/main/java/org/apache/flink/runtime/io/network/buffer/BufferBuilder.java
---
    @@ -0,0 +1,80 @@
    +/*
    + * 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.buffer;
    +
    +import org.apache.flink.core.memory.MemorySegment;
    +
    +import javax.annotation.concurrent.NotThreadSafe;
    +
    +import java.nio.ByteBuffer;
    +
    +import static org.apache.flink.util.Preconditions.checkNotNull;
    +import static org.apache.flink.util.Preconditions.checkState;
    +
    +/**
    + * Not thread safe class for filling in the initial content of the {@link Buffer}. Once
writing to the builder
    + * is complete, {@link Buffer} instance can be built and shared across multiple threads.
    + */
    +@NotThreadSafe
    +public class BufferBuilder {
    +	private final MemorySegment memorySegment;
    +
    +	private final BufferRecycler recycler;
    +
    +	private int position = 0;
    +
    +	private boolean built = false;
    +
    +	public BufferBuilder(MemorySegment memorySegment, BufferRecycler recycler) {
    +		this.memorySegment = checkNotNull(memorySegment);
    +		this.recycler = checkNotNull(recycler);
    +	}
    +
    +	public void append(ByteBuffer source) {
    +		checkState(!built);
    +
    +		int needed = source.remaining();
    +		int available = limit() - position;
    +		int toCopy = Math.min(needed, available);
    +
    +		memorySegment.put(position, source, toCopy);
    +		position += toCopy;
    +	}
    +
    +	public boolean isFull() {
    +		checkState(position <= limit());
    +		return position == limit();
    +	}
    +
    +	public Buffer build() {
    +		checkState(!built);
    +		built = true;
    +
    +		Buffer result = new Buffer(memorySegment, recycler, true, position);
    +		return result;
    --- End diff --
    
    inline `result`?


> Introduce not threadsafe write only BufferBuilder
> -------------------------------------------------
>
>                 Key: FLINK-8178
>                 URL: https://issues.apache.org/jira/browse/FLINK-8178
>             Project: Flink
>          Issue Type: Improvement
>          Components: Network
>            Reporter: Piotr Nowojski
>            Assignee: Piotr Nowojski
>             Fix For: 1.5.0
>
>
> While Buffer class is used in multithreaded context it requires synchronisation. Now
it is miss-leading/unclear and suggesting that RecordSerializer should take into account synchronisation
of the Buffer that's holding. With NotThreadSafe BufferBuilder there would be clear separation
between single-threaded writing/creating a BufferBuilder and multithreaded Buffer handling/retaining/recycling.



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