的OutOfMemoryError：無法創建使用ExecutorServie

Question

我開始了我的情況下一夜之間，看看它是如何處理的事情，當我來到這個早上，我正面臨

Exception in thread "pool-535-thread-7" java.lang.OutOfMemoryError: unable to create new native thread 
    at java.lang.Thread.start0(Native Method) 
    at java.lang.Thread.start(Thread.java:691) 
    at java.util.concurrent.ThreadPoolExecutor.addWorker(ThreadPoolExecutor.java:943) 
    at java.util.concurrent.ThreadPoolExecutor.processWorkerExit(ThreadPoolExecutor.java:992)[info] application - Connecting to server A 
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) 
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) 
    at java.lang.Thread.run(Thread.java:722) 

我的代碼的目的很新的本地線程簡單：每5分鐘，我連接到一個遠程服務器列表，發送一個請求（通過套接字），就是這樣。

這裏是我的代碼：

我 「的cron」 任務：

/** will create a new instance of ExecutorService every 5 minutes, loading all the websites in the database to check their status **/ 
/** Maybe that's where the problem is ? I need to empty (GC ?) this ExecutorService ? **/ 
Akka.system().scheduler().schedule(
    Duration.create(0, TimeUnit.MILLISECONDS), // Initial delay 0 milliseconds 
    Duration.create(5, TimeUnit.MINUTES),  // Frequency 5 minutes 
    new Runnable() { 
     public void run() { 
      // We get the list of websites to check 
      Query<Website> query = Ebean.createQuery(Website.class, "WHERE disabled = false AND removed IS NULL"); 
      query.order("created ASC"); 
      List<Website> websites = query.findList(); // Can be 1, 10, 100, 1000. In my test case, I had only 9 websites. 

      ExecutorService executor = Executors.newFixedThreadPool(NTHREDS); 
      for (Website website : websites) { 
       CheckWebsite task = new CheckWebsite(website); 
       executor.execute(task); 
      } 

      // This will make the executor accept no new threads 
      // and finish all existing threads in the queue 
      executor.shutdown(); 
     } 
    }, 
    Akka.system().dispatcher() 
); 

我CheckWebsite類：

public class CheckWebsite implements Runnable { 
    private Website website; 

    public CheckWebsite(Website website) { 
     this.website = website; 
    } 

    @Override 
    public void run() { 
     WebsiteLog log = website.checkState(); // This is where the request is made, I copy paste the code just after 
     if (log == null) { 
      Logger.error("OHOH, WebsiteLog should not be null for website.checkState() in CheckWebsite class :s"); 
      return; 
     } 

     try { 
      log.save(); 
     catch (Exception e) { 
      Logger.info ("An error occured :/"); 
      Logger.info(e.getMessage()); 
      e.printStackTrace(); 
     } 
    } 
} 

我checkState()方法Website.class：

public WebsiteLog checkState() { 
    // Since I use Socket and the connection can hang indefinitely, I use an other ExecutorService in order to limit the time spent 
    // The duration is defined via Connector.timeout, Which will be the next code. 

    ExecutorService executor = Executors.newFixedThreadPool(1); 

    Connector connector = new Connector(this); 
    try { 
     final long startTime = System.nanoTime(); 

     Future<String> future = executor.submit(connector); 
     String response = future.get(Connector.timeout, TimeUnit.MILLISECONDS); 

     long duration = System.nanoTime() - startTime; 

     return PlatformLog.getLastOccurence(this, response, ((int) duration/ 1000000)); 
    } 
    catch (Exception e) { 
     return PlatformLog.getLastOccurence(this, null, null); 
    } 
} 

這裏是Connector.class。我在這裏刪除了無用的部分（如Catches）：

public class Connector implements Callable<String> { 
    public final static int timeout = 2500; // WE use a timeout of 2.5s, which should be enough 

    private Website website; 

    public Connector(Website website) { 
     this.website = website; 
    } 

    @Override 
    public String call() throws Exception { 
     Logger.info ("Connecting to " + website.getAddress() + ":" + website.getPort()); 
     Socket socket = new Socket(); 

     try { 
      socket.connect(new InetSocketAddress(website.getIp(), website.getPort()), (timeout - 50)); 
      BufferedReader input = new BufferedReader(new InputStreamReader(socket.getInputStream())); 
      String response = input.readLine(); 
      socket.close(); 

      return response; 
     } 
     catch (Exception e) { 
      e.printStackTrace(); 
      throw e; 
     } 
     finally { 
      // I take the precaution to close the socket here in order to avoid a memory leak 
      // But if the previous ExecutorService force the close of this thread before 
      // I can't guarantee it will be closed :/ 
      if (socket != null && !socket.isClosed()) { 
       socket.close(); 
      } 
     } 
    } 
} 

我是新來的Java多線程，所以我可能犯了很大的錯誤。我懷疑一些區域，可能是潛在的原因，但我缺乏知識的要求我請求你們的幫助:)

作爲總結，這裏的潛力方面：

1. 創建一個新的ExecutorService每5分鐘。也許我可以重用舊的？或者完成後是否需要關閉當前的（如果是這樣，如何？）。
2. 我創建一個ExecutorService，將創建一個ExecutorService（在checkstate()法）
3. ，連接器類可以是（暴力）的事實由ExecutorService停止運行它，如果時間過長，造成的事實一個沒有關閉的套接字（然後是內存泄漏）？

另外，正如您所看到的，線程「pool-535-thread-7」發生異常，這意味着它很快就不會發生。

我將last_occured檢查存儲在數據庫中，並創建日誌條目（在WebsiteLog中），增量大約爲5個小時（所以，每5分鐘一次，該線程在大約60次調用後崩潰）。

更新：這裏是重新checkState方法包括關閉調用：

public PlatformLog checkState() { 
    ExecutorService executor = Executors.newFixedThreadPool(1); 

    Connector connector = new Connector(this); 
    String response = null; 
    Long duration = null; 

    try { 
     final long startTime = System.nanoTime(); 

     Future<String> future = executor.submit(connector); 
     response = future.get(Connector.timeout, TimeUnit.MILLISECONDS); 

     duration = System.nanoTime() - startTime; 
    } 
    catch (Exception e) {} 

    executor.shutdown(); 
    if (duration != null) { 
     return WebsiteLog.getLastOccurence(this, response, (duration.intValue()/ 1000000)); 
    } 
    else { 
     return WebsiteLog.getLastOccurence(this, response, null); 
    } 
} 

Answer 1

我不知道這是唯一的問題，但你在你的checkState()方法創建ExecutorService但你不關閉了。

按照JavaDoc中Executors.newFixedThreadPool()：

The threads in the pool will exist until it is explicitly shutdown.

的線程活着會導致ExecutorServicenot to be garbage collected（這將調用shutdown()代表你所以你每次這個被調用時泄漏線程。