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Java Scheduled Executor线程进入等待状态

[英]Java Scheduled Executor Threads going into Waiting State

 原文  2018-05-21 14:40:36  9   1    java/ multithreading/ sockets/ asynchronous/ jedis

问题描述

因此，我正在尝试使用两个自定义线程以及计划的线程执行器来实现从Java客户端到Go服务器的基本异步消息传递协议。 因此，我启动了一个从Java客户端到Go服务器的TCP套接字，并在两侧设置了读写缓冲区。

Writer线程将与每个请求相对应的唯一ID保存到Redis服务器中，并在TCP套接字上使用PrintWriter写入请求。

WriterThread 

public class WithdrawRequestWriter extends Thread {

    private static final int START_ACCOUNT_NO = 1;
    private static final int END_ACCOUNT_NO = 2_000;
    private static final int AMOUNT_TO_WITHDRAW = 100;

    private PrintWriter writer;
    private Jedis jedis;

    public WithdrawRequestWriter(PrintWriter writer, Jedis jedis) {
        this.writer = writer;
        this.jedis = jedis;
    }

    @Override
    public void run() {
        int i = 0;
        for (int accountNo = START_ACCOUNT_NO; accountNo <= END_ACCOUNT_NO; accountNo++) {
            String uniqueId = UUID.randomUUID().toString();
            if (jedis.set(uniqueId, String.valueOf(accountNo), "NX", "EX", 10) != null) {
                writer.write(uniqueId + " " + accountNo + " " + AMOUNT_TO_WITHDRAW + "\n");
                writer.flush();
            } else {
                System.err.println("Setting of UUID in redis failed: " + uniqueId);
            }
        }
    }
}

同样，读取器线程等待服务器的响应。 一旦收到一个，它就与Redis中的唯一ID相匹配，并将它们标记为完成（成功/失败）。

ReaderThread 

public class WithdrawRequestReader extends Thread {

    private BufferedReader reader;
    private Jedis jedis;


    public WithdrawRequestReader(BufferedReader reader, Jedis jedis) {
        this.reader = reader;
        this.jedis = jedis;
    }

    @Override
    public void run() {
        String response;
        while (true) {
            try {
                if ((response = reader.readLine()) != null) {
                    String[] tokenizedResponse = response.split(" ");
                    System.out.println("Response is: " + response);
                    String value = jedis.get(tokenizedResponse[0]);
                    if (value != null) {
                        System.out.println("Request Token: " + tokenizedResponse[0]
                                + " | Status: " + tokenizedResponse[1]
                                + " | Account: " + tokenizedResponse[2]
                                + " | Amount: " + tokenizedResponse[3]
                                + " | Remaining Balance: " + tokenizedResponse[4]
                                + " | ResponeStr: " + tokenizedResponse[5]);
                    }
                } else {
                    System.out.println("Waiting for response...");
                }
            } catch (IOException ex) {
                ex.printStackTrace();
                System.exit(3);
            }
        }
    }
}

主线 

public class TestClient {

    private static final String HOSTNAME = "localhost";
    private static final int PORT = 12410;

    public static void main(String[] args) throws IOException {

        Socket socket = new Socket(HOSTNAME, PORT);
        PrintWriter writer = new PrintWriter(socket.getOutputStream());
        BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        Jedis jedis = new Jedis("localhost");

        ScheduledExecutorService scheduledExecutorService = Executors.newScheduledThreadPool(2);
//        ScheduledExecutorService scheduledExecutorService = Executors.newSingleThreadScheduledExecutor();
        WithdrawRequestReader readerThread = new WithdrawRequestReader(reader, jedis);
        WithdrawRequestWriter writerThread = new WithdrawRequestWriter(writer, jedis);
        scheduledExecutorService.schedule(writerThread, 0, TimeUnit.MILLISECONDS);
        scheduledExecutorService.schedule(readerThread, 0, TimeUnit.MILLISECONDS);
    }
}

当我使用singlePoolThreadExecutor时，任务将按顺序执行（如预期的那样），一切都会顺利进行。 但是，当我将threadPoolExecutor与两个线程一起使用时，经过几次读写操作，它们会无限期地进入等待状态。 我从网上提供的免费工具中检查了是否存在死锁，但没有任何帮助。 当它们被卡住时，下面是线程转储。

线程转储 

Full thread dump Java HotSpot(TM) 64-Bit Server VM (9.0.4+11 mixed mode):

"DestroyJavaVM" #16 prio=5 os_prio=31 tid=0x00007f974e06d000 nid=0x2503 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"pool-1-thread-2" #15 prio=5 os_prio=31 tid=0x00007f974e06c000 nid=0x6003 waiting on condition [0x000070000c819000]
   java.lang.Thread.State: WAITING (parking)
    at jdk.internal.misc.Unsafe.park(java.base@9.0.4/Native Method)
    - parking to wait for  <0x0000000747cf64b0> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
    at java.util.concurrent.locks.LockSupport.park(java.base@9.0.4/LockSupport.java:194)
    at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(java.base@9.0.4/AbstractQueuedSynchronizer.java:2062)
    at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(java.base@9.0.4/ScheduledThreadPoolExecutor.java:1119)
    at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(java.base@9.0.4/ScheduledThreadPoolExecutor.java:848)
    at java.util.concurrent.ThreadPoolExecutor.getTask(java.base@9.0.4/ThreadPoolExecutor.java:1092)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(java.base@9.0.4/ThreadPoolExecutor.java:1152)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(java.base@9.0.4/ThreadPoolExecutor.java:641)
    at java.lang.Thread.run(java.base@9.0.4/Thread.java:844)

"pool-1-thread-1" #14 prio=5 os_prio=31 tid=0x00007f974e8a9800 nid=0x5e03 waiting on condition [0x000070000c716000]
   java.lang.Thread.State: WAITING (parking)
    at jdk.internal.misc.Unsafe.park(java.base@9.0.4/Native Method)
    - parking to wait for  <0x0000000747cf64b0> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
    at java.util.concurrent.locks.LockSupport.park(java.base@9.0.4/LockSupport.java:194)
    at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(java.base@9.0.4/AbstractQueuedSynchronizer.java:2062)
    at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(java.base@9.0.4/ScheduledThreadPoolExecutor.java:1119)
    at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(java.base@9.0.4/ScheduledThreadPoolExecutor.java:848)
    at java.util.concurrent.ThreadPoolExecutor.getTask(java.base@9.0.4/ThreadPoolExecutor.java:1092)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(java.base@9.0.4/ThreadPoolExecutor.java:1152)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(java.base@9.0.4/ThreadPoolExecutor.java:641)
    at java.lang.Thread.run(java.base@9.0.4/Thread.java:844)

"Service Thread" #11 daemon prio=9 os_prio=31 tid=0x00007f974d827000 nid=0xa003 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Monitor Ctrl-Break" #10 daemon prio=5 os_prio=31 tid=0x00007f974e078800 nid=0x5903 runnable [0x000070000c40d000]
   java.lang.Thread.State: RUNNABLE
    at java.net.SocketInputStream.socketRead0(java.base@9.0.4/Native Method)
    at java.net.SocketInputStream.socketRead(java.base@9.0.4/SocketInputStream.java:116)
    at java.net.SocketInputStream.read(java.base@9.0.4/SocketInputStream.java:171)
    at java.net.SocketInputStream.read(java.base@9.0.4/SocketInputStream.java:141)
    at sun.nio.cs.StreamDecoder.readBytes(java.base@9.0.4/StreamDecoder.java:284)
    at sun.nio.cs.StreamDecoder.implRead(java.base@9.0.4/StreamDecoder.java:326)
    at sun.nio.cs.StreamDecoder.read(java.base@9.0.4/StreamDecoder.java:178)
    - locked <0x0000000747d9ea78> (a java.io.InputStreamReader)
    at java.io.InputStreamReader.read(java.base@9.0.4/InputStreamReader.java:185)
    at java.io.BufferedReader.fill(java.base@9.0.4/BufferedReader.java:161)
    at java.io.BufferedReader.readLine(java.base@9.0.4/BufferedReader.java:326)
    - locked <0x0000000747d9ea78> (a java.io.InputStreamReader)
    at java.io.BufferedReader.readLine(java.base@9.0.4/BufferedReader.java:392)
    at com.intellij.rt.execution.application.AppMainV2$1.run(AppMainV2.java:64)

"Common-Cleaner" #9 daemon prio=8 os_prio=31 tid=0x00007f974e00a000 nid=0xa203 in Object.wait() [0x000070000c30a000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
    at java.lang.Object.wait(java.base@9.0.4/Native Method)
    - waiting on <0x0000000747f37610> (a java.lang.ref.ReferenceQueue$Lock)
    at java.lang.ref.ReferenceQueue.remove(java.base@9.0.4/ReferenceQueue.java:151)
    - waiting to re-lock in wait() <0x0000000747f37610> (a java.lang.ref.ReferenceQueue$Lock)
    at jdk.internal.ref.CleanerImpl.run(java.base@9.0.4/CleanerImpl.java:148)
    at java.lang.Thread.run(java.base@9.0.4/Thread.java:844)
    at jdk.internal.misc.InnocuousThread.run(java.base@9.0.4/InnocuousThread.java:122)

"Sweeper thread" #8 daemon prio=9 os_prio=31 tid=0x00007f974d81c000 nid=0x5803 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"C1 CompilerThread2" #7 daemon prio=9 os_prio=31 tid=0x00007f974d81b000 nid=0xa503 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE
   No compile task

"C2 CompilerThread1" #6 daemon prio=9 os_prio=31 tid=0x00007f974e005000 nid=0xa603 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE
   No compile task

"C2 CompilerThread0" #5 daemon prio=9 os_prio=31 tid=0x00007f974d81a800 nid=0xa803 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE
   No compile task

"Signal Dispatcher" #4 daemon prio=9 os_prio=31 tid=0x00007f974e01a800 nid=0x5603 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Finalizer" #3 daemon prio=8 os_prio=31 tid=0x00007f974d041800 nid=0x4003 in Object.wait() [0x000070000bc75000]
   java.lang.Thread.State: WAITING (on object monitor)
    at java.lang.Object.wait(java.base@9.0.4/Native Method)
    - waiting on <0x0000000747f0d078> (a java.lang.ref.ReferenceQueue$Lock)
    at java.lang.ref.ReferenceQueue.remove(java.base@9.0.4/ReferenceQueue.java:151)
    - waiting to re-lock in wait() <0x0000000747f0d078> (a java.lang.ref.ReferenceQueue$Lock)
    at java.lang.ref.ReferenceQueue.remove(java.base@9.0.4/ReferenceQueue.java:172)
    at java.lang.ref.Finalizer$FinalizerThread.run(java.base@9.0.4/Finalizer.java:216)

"Reference Handler" #2 daemon prio=10 os_prio=31 tid=0x00007f974d040800 nid=0x4103 waiting on condition [0x000070000bb72000]
   java.lang.Thread.State: RUNNABLE
    at java.lang.ref.Reference.waitForReferencePendingList(java.base@9.0.4/Native Method)
    at java.lang.ref.Reference.processPendingReferences(java.base@9.0.4/Reference.java:174)
    at java.lang.ref.Reference.access$000(java.base@9.0.4/Reference.java:44)
    at java.lang.ref.Reference$ReferenceHandler.run(java.base@9.0.4/Reference.java:138)

"VM Thread" os_prio=31 tid=0x00007f974e884000 nid=0x4303 runnable 

"GC Thread#0" os_prio=31 tid=0x00007f974e80d800 nid=0x2a03 runnable 

"GC Thread#1" os_prio=31 tid=0x00007f974e80e800 nid=0x5303 runnable 

"GC Thread#2" os_prio=31 tid=0x00007f974d80c800 nid=0x2b03 runnable 

"GC Thread#3" os_prio=31 tid=0x00007f974d000800 nid=0x2c03 runnable 

"G1 Main Marker" os_prio=31 tid=0x00007f974e835800 nid=0x4803 runnable 

"G1 Marker#0" os_prio=31 tid=0x00007f974d80d800 nid=0x4503 runnable 

"G1 Refine#0" os_prio=31 tid=0x00007f974e80f800 nid=0x4a03 runnable 

"G1 Refine#1" os_prio=31 tid=0x00007f974d80d000 nid=0x4c03 runnable 

"G1 Refine#2" os_prio=31 tid=0x00007f974e80f000 nid=0x4e03 runnable 

"G1 Refine#3" os_prio=31 tid=0x00007f974e806800 nid=0x5003 runnable 

"G1 Young RemSet Sampling" os_prio=31 tid=0x00007f974e810800 nid=0x2f03 runnable 

"VM Periodic Task Thread" os_prio=31 tid=0x00007f974e079800 nid=0x5c03 waiting on condition 

JNI global references: 421

Heap
 garbage-first heap   total 131072K, used 10240K [0x0000000740000000, 0x0000000740100400, 0x00000007c0000000)
  region size 1024K, 11 young (11264K), 0 survivors (0K)
 Metaspace       used 8824K, capacity 9274K, committed 9472K, reserved 1058816K
  class space    used 832K, capacity 927K, committed 1024K, reserved 1048576K

我相信Go服务器不是问题，否则单线程执行器也应该卡住，但不是。 可能是我陷入了僵局，但无法找出确切原因。 有人可以帮忙吗？ 如果您还有其他需要，请告诉我。

1 个解决方案

解决方案1
 0 已采纳  2018-05-22 12:48:39

代码的套接字和流部分似乎是正确的。 并行使用套接字的输入和输出流是正确的，因为它们是独立的流。

问题是Jedis组件。 Jedis不是线程安全的。 Jedis文档说：

您不应该使用来自不同线程的同一实例，因为您会遇到奇怪的错误。 有时创建大量的Jedis实例还不够好，因为这意味着大量的套接字和连接，这也会导致奇怪的错误。 单个Jedis实例不是线程安全的！...

重写代码是必要的，以便每个线程都有Jedis的私有实例。

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