Elasticsearch 6.1.0線程池介紹

開篇

?這篇文章主要是用來講解ES線程池(EsExecutors)的實(shí)現(xiàn)，然后象征性的和JDK的Executors實(shí)現(xiàn)進(jìn)行了簡單的對比挑宠，看了這篇文章以后要對Executors和ThreadPoolExecutor的使用更有信心才對菲盾。

elasticsearch線程池配置

public class ThreadPool extends AbstractComponent implements Scheduler, Closeable {

  final int availableProcessors = EsExecutors.numberOfProcessors(settings);
  final int halfProcMaxAt5 = halfNumberOfProcessorsMaxFive(availableProcessors);
  final int halfProcMaxAt10 = halfNumberOfProcessorsMaxTen(availableProcessors);
  final int genericThreadPoolMax = boundedBy(4 * availableProcessors, 128, 512);

  builders.put(Names.GENERIC, 
  new ScalingExecutorBuilder(Names.GENERIC, 4, genericThreadPoolMax, TimeValue.timeValueSeconds(30)));

  builders.put(Names.INDEX, 
  new FixedExecutorBuilder(settings, Names.INDEX, availableProcessors, 200));

  builders.put(Names.BULK, 
  new FixedExecutorBuilder(settings, Names.BULK, availableProcessors, 200)); 

  builders.put(Names.GET, 
  new FixedExecutorBuilder(settings, Names.GET, availableProcessors, 1000));

  builders.put(Names.SEARCH, 
  new AutoQueueAdjustingExecutorBuilder(settings,
                        Names.SEARCH, searchThreadPoolSize(availableProcessors), 1000, 1000, 1000, 2000));

  builders.put(Names.MANAGEMENT, 
  new ScalingExecutorBuilder(Names.MANAGEMENT, 1, 5, TimeValue.timeValueMinutes(5)));

  builders.put(Names.LISTENER, 
  new FixedExecutorBuilder(settings, Names.LISTENER, halfProcMaxAt10, -1));

  builders.put(Names.FLUSH, 
  new ScalingExecutorBuilder(Names.FLUSH, 1, halfProcMaxAt5, TimeValue.timeValueMinutes(5)));

  builders.put(Names.REFRESH, 
  new ScalingExecutorBuilder(Names.REFRESH, 1, halfProcMaxAt10, TimeValue.timeValueMinutes(5)));

  builders.put(Names.WARMER, 
  new ScalingExecutorBuilder(Names.WARMER, 1, halfProcMaxAt5, TimeValue.timeValueMinutes(5)));

  builders.put(Names.SNAPSHOT, 
  new ScalingExecutorBuilder(Names.SNAPSHOT, 1, halfProcMaxAt5, TimeValue.timeValueMinutes(5)));

  builders.put(Names.FETCH_SHARD_STARTED, 
  new ScalingExecutorBuilder(Names.FETCH_SHARD_STARTED, 1, 2 * availableProcessors, TimeValue.timeValueMinutes(5)));

  builders.put(Names.FORCE_MERGE, 
  new FixedExecutorBuilder(settings, Names.FORCE_MERGE, 1, -1));

  builders.put(Names.FETCH_SHARD_STORE, 
  new ScalingExecutorBuilder(Names.FETCH_SHARD_STORE, 1, 2 * availableProcessors, TimeValue.timeValueMinutes(5)));
}

說明：

elasticsearch線程池根據(jù)作用的不同主要分為兩大類 ScalingExecutor和FixedExecutor。
ScalingExecutor表示線程池中的線程數(shù)是動(dòng)態(tài)可變的各淀。
FixedExecutor表示線程池中的線程池是不可變的懒鉴。

elasticsearch線程池分類

elasticsearch線程池的線程按照源碼的實(shí)現(xiàn)來看分為FIXED和SCALING兩大類，FIXED的意思是固定線程的數(shù)量（core thread個(gè)數(shù) = max thread個(gè)數(shù)）揪阿，SCALING的意思是動(dòng)態(tài)調(diào)整線程數(shù)量（core thread個(gè)數(shù) != max thread個(gè)數(shù)）疗我。

FIXED

說明：大小固定設(shè)置的threadpool，它有一個(gè)queue來存放pending的請求南捂，其中pool的大小默認(rèn)是core*5吴裤，queue_size默認(rèn)是-1(即是無限制)。

LISTENER：用作client的操作溺健，默認(rèn)大小halfProcMaxAt10麦牺，queue_size=-1無限制；
GET：用作get操作鞭缭，默認(rèn)大小availableProcessors剖膳，queue_size為1000；
INDEX：用作index或delete操作岭辣，默認(rèn)大小availableProcessors吱晒，queue_size為200；
BULK：用作bulk操作沦童，默認(rèn)大小為availableProcessors仑濒，queue_size為200叹话；
SEARCH：用作count或是search操作，默認(rèn)大小((availableProcessors * 3) / 2) + 1墩瞳；queue_size為1000驼壶；
SUGGEST：用作suggest操作，默認(rèn)大小availableProcessors喉酌，queue_size為1000热凹；
PERCOLATE：用作percolate，默認(rèn)大小為availableProcessors泪电，queue_size為1000般妙；
FORCE_MERGE：用作force_merge操作(2.1之前叫做optimize)，默認(rèn)大小為1歪架；

SCALING

說明：擁有可變大小的pool股冗，其值可在1和設(shè)置值之間。

GENERIC：通用的操作和蚪，比如node的discovery，默認(rèn)大小genericThreadPoolMax烹棉，默認(rèn)keep alive時(shí)間是30sec;
MANAGEMENT：用作ES的管理攒霹，比如集群的管理；默認(rèn)大小5浆洗，keep alive時(shí)間為5min催束；
FLUSH：用作flush操作，默認(rèn)大小為halfProcMaxAt5伏社，keep alive時(shí)間為5min抠刺；
REFRESH：用作refresh操作，默認(rèn)大小為halfProcMaxAt10摘昌，keep alive時(shí)間為5min速妖；
WARMER：用作index warm-up操作，默認(rèn)大小為halfProcMaxAt5聪黎，keep alive時(shí)間為5min罕容；
SNAPSHOT:用作snapshot操作，默認(rèn)大小為halfProcMaxAt5稿饰，keep alive時(shí)間為5min锦秒；
FETCH_SHARD_STARTED：用作fetch shard開始操作，默認(rèn)大小availableProcessors * 2喉镰，keep alive時(shí)間為5min旅择；
FETCH_SHARD_STORE：用作fetch shard存儲(chǔ)操作，默認(rèn)大小availableProcessors * 2侣姆，keep alive時(shí)間為5min生真；

JDK的Executors

public class Executors {

    public static ExecutorService newFixedThreadPool(int nThreads) {
        return new ThreadPoolExecutor(nThreads, nThreads,
                                      0L, TimeUnit.MILLISECONDS,
                                      new LinkedBlockingQueue<Runnable>());
    }

    public static ExecutorService newFixedThreadPool(int nThreads, ThreadFactory threadFactory) {
        return new ThreadPoolExecutor(nThreads, nThreads,
                                      0L, TimeUnit.MILLISECONDS,
                                      new LinkedBlockingQueue<Runnable>(),
                                      threadFactory);
    }

    public static ExecutorService newCachedThreadPool() {
        return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
                                      60L, TimeUnit.SECONDS,
                                      new SynchronousQueue<Runnable>());
    }

    public static ExecutorService newCachedThreadPool(ThreadFactory threadFactory) {
        return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
                                      60L, TimeUnit.SECONDS,
                                      new SynchronousQueue<Runnable>(),
                                      threadFactory);
    }
}

說明：

Executors的newFixedThreadPool創(chuàng)建固定線程數(shù)量的線程池脖咐。
Executors的newCachedThreadPool創(chuàng)建可動(dòng)態(tài)調(diào)整線程數(shù)量的線程池。
Executors創(chuàng)建的是ThreadPoolExecutor對象汇歹。

Elasticsearch的EsExecutors

public class EsExecutors {

    public static final Setting<Integer> PROCESSORS_SETTING =
        Setting.intSetting("processors", Runtime.getRuntime().availableProcessors(), 1, Property.NodeScope);

    public static int numberOfProcessors(final Settings settings) {
        return PROCESSORS_SETTING.get(settings);
    }

    public static EsThreadPoolExecutor newScaling(String name, int min, int max, long keepAliveTime, 
                          TimeUnit unit, ThreadFactory threadFactory, ThreadContext contextHolder) {
        ExecutorScalingQueue<Runnable> queue = new ExecutorScalingQueue<>();
        EsThreadPoolExecutor executor = new EsThreadPoolExecutor(name, min, max, keepAliveTime, 
                            unit, queue, threadFactory, new ForceQueuePolicy(), contextHolder);
        queue.executor = executor;
        return executor;
    }

    public static EsThreadPoolExecutor newFixed(String name, int size, int queueCapacity, 
                             ThreadFactory threadFactory, ThreadContext contextHolder) {
        BlockingQueue<Runnable> queue;
        if (queueCapacity < 0) {
            queue = ConcurrentCollections.newBlockingQueue();
        } else {
            queue = new SizeBlockingQueue<>(ConcurrentCollections.<Runnable>newBlockingQueue(), queueCapacity);
        }
        return new EsThreadPoolExecutor(name, size, size, 0, TimeUnit.MILLISECONDS, queue, 
                                        threadFactory, new EsAbortPolicy(), contextHolder);
    }

    public static EsThreadPoolExecutor newAutoQueueFixed(String name, int size, int initialQueueCapacity, int minQueueSize,
                                                         int maxQueueSize, int frameSize, TimeValue targetedResponseTime,
                                                         ThreadFactory threadFactory, ThreadContext contextHolder) {
        if (initialQueueCapacity <= 0) {
            throw new IllegalArgumentException("initial queue capacity for [" + name + "] executor must be positive, got: " +
                            initialQueueCapacity);
        }
        ResizableBlockingQueue<Runnable> queue =
                new ResizableBlockingQueue<>(ConcurrentCollections.<Runnable>newBlockingQueue(), initialQueueCapacity);
        return new QueueResizingEsThreadPoolExecutor(name, size, size, 0, TimeUnit.MILLISECONDS,
                queue, minQueueSize, maxQueueSize, TimedRunnable::new, frameSize, targetedResponseTime, threadFactory,
                new EsAbortPolicy(), contextHolder);
    }
}

說明：

newScaling()方法創(chuàng)建可擴(kuò)展線程數(shù)量的線程池屁擅，淘汰策略使用ForceQueuePolicy。
newFixed()方法創(chuàng)建創(chuàng)建固定線程數(shù)量的線程池产弹，淘汰策略使用EsAbortPolicy派歌。
newAutoQueueFixed()方法創(chuàng)建固定線程數(shù)量但是Queue隊(duì)列數(shù)量可以動(dòng)態(tài)調(diào)整的線程池，淘汰策略使用EsAbortPolicy痰哨。胶果。
EsExecutors內(nèi)部創(chuàng)建的是EsThreadPoolExecutor對象。
EsExecutors的實(shí)現(xiàn)借鑒了JDK的Executors接口斤斧，給我們提供了自定Executors的思路早抠。

EsExecutors的EsThreadPoolExecutor

public class EsThreadPoolExecutor extends ThreadPoolExecutor {
    EsThreadPoolExecutor(String name, int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit,
            BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory, ThreadContext contextHolder) {
        this(name, corePoolSize, maximumPoolSize, keepAliveTime, unit, 
             workQueue, threadFactory, new EsAbortPolicy(), contextHolder);
    }

    EsThreadPoolExecutor(String name, int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit,
            BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory, XRejectedExecutionHandler handler,
            ThreadContext contextHolder) {
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory, handler);
        this.name = name;
        this.contextHolder = contextHolder;
    }

    @Override
    public void execute(final Runnable command) {
        doExecute(wrapRunnable(command));
    }

    protected void doExecute(final Runnable command) {
        try {
            super.execute(command);
        } catch (EsRejectedExecutionException ex) {
            if (command instanceof AbstractRunnable) {
                try {
                    ((AbstractRunnable) command).onRejection(ex);
                } finally {
                    ((AbstractRunnable) command).onAfter();

                }
            } else {
                throw ex;
            }
        }
    }

    @Override
    protected void afterExecute(Runnable r, Throwable t) {
        super.afterExecute(r, t);
        assert assertDefaultContext(r);
    }
}

說明：

EsThreadPoolExecutor繼承自ThreadPoolExecutor對象，構(gòu)造函數(shù)內(nèi)部初始化ThreadPoolExecutor對象撬讽。
EsThreadPoolExecutor的核心的execute方法內(nèi)部也是調(diào)用了ThreadPoolExecutor的execute方法蕊连。
EsThreadPoolExecutor重新了execute和afterExecute方法。
EsThreadPoolExecutor給我們提供了重寫ThreadPoolExecutor的思路游昼，值得學(xué)習(xí)甘苍。

EsExecutors的ThreadFactory

public class EsExecutors {

    public static String threadName(Settings settings, String ... names) {
        String namePrefix =
                Arrays
                        .stream(names)
                        .filter(name -> name != null)
                        .collect(Collectors.joining(".", "[", "]"));
        return threadName(settings, namePrefix);
    }

    public static ThreadFactory daemonThreadFactory(String namePrefix) {
        return new EsThreadFactory(namePrefix);
    }

    static class EsThreadFactory implements ThreadFactory {

        final ThreadGroup group;
        final AtomicInteger threadNumber = new AtomicInteger(1);
        final String namePrefix;

        EsThreadFactory(String namePrefix) {
            this.namePrefix = namePrefix;
            SecurityManager s = System.getSecurityManager();
            group = (s != null) ? s.getThreadGroup() :
                    Thread.currentThread().getThreadGroup();
        }

        @Override
        public Thread newThread(Runnable r) {
            Thread t = new Thread(group, r,
                    namePrefix + "[T#" + threadNumber.getAndIncrement() + "]",
                    0);
            t.setDaemon(true);
            return t;
        }
    }

    private EsExecutors() {
    }
}

說明：

1.EsExecutors給我們提供一種創(chuàng)建線程工廠的標(biāo)準(zhǔn)方法，實(shí)現(xiàn)ThreadFactory接口重新newThread()方法烘豌。
2.通過AtomicInteger threadNumber = new AtomicInteger(1)變量生成線程自增的線程id载庭。
3.線程池的線程都有具體意義的線程名非常重要有利于排查問題，非常推薦使用廊佩。

EsExecutors的AbortPolicy

public interface XRejectedExecutionHandler extends RejectedExecutionHandler {
    long rejected();
}

public class EsAbortPolicy implements XRejectedExecutionHandler {
    private final CounterMetric rejected = new CounterMetric();

    @Override
    public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {
        if (r instanceof AbstractRunnable) {
            if (((AbstractRunnable) r).isForceExecution()) {
                BlockingQueue<Runnable> queue = executor.getQueue();
                if (!(queue instanceof SizeBlockingQueue)) {
                    throw new IllegalStateException("forced execution, but expected a size queue");
                }
                try {
                    ((SizeBlockingQueue) queue).forcePut(r);
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                    throw new IllegalStateException("forced execution, but got interrupted", e);
                }
                return;
            }
        }
        rejected.inc();
        throw new EsRejectedExecutionException("rejected execution of " + r + " on " + executor, executor.isShutdown());
    }

    public long rejected() {
        return rejected.count();
    }
}


static class ForceQueuePolicy implements XRejectedExecutionHandler {
        @Override
        public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {
            try {
                executor.getQueue().put(r);
            } catch (InterruptedException e) {
                throw new EsRejectedExecutionException(e);
            }
        }

        @Override
        public long rejected() {
            return 0;
        }
    }

說明：

EsAbortPolicy的過期策略提供了我們自定實(shí)現(xiàn)過期策略的案例囚聚。

參考文章

源碼Elasticsearch源碼3(線程池)