Java并行序列化和压缩

Question

我有一个JavaSE8应用程序，用于并行处理大型数据集。我正在生成1M对象，我想将其序列化为单个压缩文件。该文件将从Web应用程序下载/上传。并行过程得到了很好的优化。然而，序列化/压缩是按顺序完成的，它是我的应用程序的瓶颈。

我测试了不同的解决方案：Kryo，ChronicleMap ......我现在正在使用Kryo和Bz2压缩。它正在发挥作用。但表现不够好。

我找不到任何进行并行序列化和压缩的解决方案。欢迎提供此方面的任何信息

Answer 1

实际上并行或顺序处理数据集的方式实际上并不重要，因为在清晰的设计中 - 序列化始终是顺序的（由于输出流，套接字等的连续性）操作并且不在数据集处理之外。因此，如果您要序列化并将序列化数据集放入文件，连接或原始内存中，则必须定义一个屏障，以保护数据免受并发竞争和不期望的修改。

当然，有些情况下每个工作线程序列化数据本身，例如http服务器工作，但在这里我们讨论的是并行处理并最终序列化的单个数据集。

所以，根据上面的说法，它应该是一个正确的答案。它使用标准的Java序列化+ GZIP压缩。您可以在此代码中轻松替换序列化和/或压缩，并针对当前解决方案进行基准测试。

package com.example.demo;

import java.io.*;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;

import static java.lang.String.format;

public final class ParallelObjectsSerialization {

    private static final int ONE_MILLION = 1_000_000;
    private static final String SERIALIZE_FILE = "/tmp/out.bin";

    public static void main(String[] args) throws IOException, ClassNotFoundException {
//        List<Player> players = parallelGenerate1MPlayers();
        List<Player> players = seqGenerate1MPlayers();
        serialize(players);
        players.clear();
        players = deserialize();
    }

    private static List<Player> deserialize() throws IOException, ClassNotFoundException {
        long started = System.currentTimeMillis();
        List<Player> players = new ArrayList<>();
        try (ObjectInputStream in = new ObjectInputStream(new GZIPInputStream(new FileInputStream(SERIALIZE_FILE)))) {
            for (int i = 0; i < ONE_MILLION; i++) {
                players.add((Player) in.readObject());
            }
        }
        long time = System.currentTimeMillis() - started;
        System.out.println(format("deserialization of %d objects took %d ms", players.size(), time));
        return players;
    }

    private static final class Player implements Serializable {
        private final String name;
        private final int level;

        private Player(String name, int level) {
            this.name = name;
            this.level = level;
        }
    }

    private static List<Player> seqGenerate1MPlayers() {
        long started = System.currentTimeMillis();
        List<Player> players = new ArrayList<>(ONE_MILLION);
        for (int i = 0; i < ONE_MILLION; i++) {
            players.add(new Player(randomName(i), i));
        }
        long time = System.currentTimeMillis() - started;
        System.out.println(format("sequential generating of %d objects took %d ms", players.size(), time));
        return players;
    }

    private static List<Player> parallelGenerate1MPlayers() {
        long started = System.currentTimeMillis();
        Player[] players = new Player[ONE_MILLION];
        Arrays.parallelSetAll(players, (i) -> new Player(randomName(i), i));
        long time = System.currentTimeMillis() - started;
        System.out.println(format("parallel generating of %d objects took %d ms", players.length, time));
        return Arrays.asList(players);
    }

    private static void serialize(List<Player> players) throws IOException {
        long started = System.currentTimeMillis();
        try (ObjectOutputStream out = new ObjectOutputStream(new GZIPOutputStream(new FileOutputStream(SERIALIZE_FILE)))) {
            for (Player player : players) {
                out.writeObject(player);
            }
        }
        long time = System.currentTimeMillis() - started;
        System.out.println(format("serialization of %d objects took %d ms", players.size(), time));
    }

    private static String randomName(int seed) {
        StringBuilder builder = new StringBuilder();
        double chance = 30.0;
        for (char c = 'a'; c <= 'z'; c++) {
            if (Math.random() * 100.0 <= chance) {
                builder.append(c);
                if (builder.length() == 7) {
                    break;
                }
            }
        }
        if (builder.length() == 0) {
            builder.append("unknown").append(seed);
        }
        return builder.toString();
    }
}