ZooKeeper分散式任務排程中心

百聯達發表於2017-04-25
原文網址 : http://blog.itpub.net/28624388/viewspace-2137933/
分散式
一： 背景

軟體系統中，定時任務往往不可或缺，大家可能會採用Spring quartz 建立定時任務模組。 當任務模組進行了分散式部署，通常會出現定時任務重複執行的情況。 怎麼避免這種情況呢，是否可以構建一個任務註冊中心，Quartz負責註冊任務，但不具體執行任務內的業務邏輯。

任務註冊中心解決任務重複註冊的問題，同時將任務分配給若干處理器進行具體的業務處理，保證在同一個時間內，一個任務只會被一個處理器進行處理。如下圖



二：任務註冊中心與排程中心

採用ZooKeeper的客戶端框架Curator,  利用ZooKeeper的Master選舉機制實現。 註冊任務就相當於在ZooKeeper中建立或更新一個節點。通過更新節點的內容，來記錄任務的執行狀態。

三：程式碼模擬


點選(此處)摺疊或開啟

  1. public class ZookeeperDemo5 {

  3.     private static String PATH = "/zkbk2";
  4.     private static String FINISH_FLAG="finish";

  6.     private static CuratorFramework client = CuratorFrameworkFactory.builder()
  7.             .connectString("10.243.3.18:2181,10.243.3.17:2181,10.243.3.27:2181").sessionTimeoutMs(5000)
  8.             .retryPolicy(new ExponentialBackoffRetry(100, 3)).build();

  10.     public static void main(String[] args) throws Exception {
  11.         client.start();
  12.         PathChildrenCache cache = new PathChildrenCache(client, PATH, true);
  13.         cache.start(StartMode.POST_INITIALIZED_EVENT);

  15.         cache.getListenable().addListener(new PathChildrenCacheListener() {

  17.             @Override
  18.             public void childEvent(CuratorFramework client, PathChildrenCacheEvent event) {
  19.                 switch (event.getType()) {
  20.                     case CHILD_ADDED:
  21.                         System.out.println("CHILD_ADDED," + event.getData().getPath());
  22.                         deal(event);
  23.                         break;
  24.                     case CHILD_UPDATED:
  25.                         System.out.println("CHILD_UPDATED," + event.getData().getPath());
  26.                         deal(event);
  27.                         break;
  28.                     case CHILD_REMOVED:
  29.                         System.out.println("CHILD_REMOVED," + event.getData().getPath());
  30.                         break;
  31.                     default:
  32.                         break;
  33.                 }
  34.             }
  35.         });

  37.        Thread.sleep(Integer.MAX_VALUE);
  38.     }
  39.     
  40.     
  41.     
  42.     
  43.     private static void deal( PathChildrenCacheEvent event)
  44.     {
  45.         final LeaderLatch latch = new LeaderLatch(client, event.getData().getPath());

  47.         latch.addListener(new LeaderLatchListener() {

  49.             @Override
  50.             public void notLeader() {
  51.             }

  53.             @Override
  54.             public void isLeader() {
  55.                 try {
  56.                     System.out.println("======begin deal==========" + event.getData().getPath());

  58.                     String data = new String(client.getData().forPath(event.getData().getPath()));
  59.                    

  61.                     if (!data.contains("finish")) {
  62.                         Thread.sleep(10000L);
  63.                         System.out.println("");
  64.                         System.out.println("");
  65.                         System.out.println("**************************************");
  66.                         System.out.println("**************************************");
  67.                         System.out.println("**************************************");
  68.                         System.out.println("**************************************");
  69.                         System.out.println("");
  70.                         System.out.println("");
  71.                         client.setData().forPath(event.getData().getPath(), FINISH_FLAG.getBytes());
  72.                     }
  73.                     System.out.println("======finish deal==========" + event.getData().getPath());
  74.                     latch.close();
  75.                 }
  76.                 catch (Exception e) {
  77.                     e.printStackTrace();
  78.                 }
  79.             }
  80.         });
  81.         try {
  82.             latch.start();
  83.         }
  84.         catch (Exception e) {
  85.             e.printStackTrace();
  86.         }
  87.     }
  88. }


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