ZooKeeper中边边角角的知识总结_角角边边边角总结-优快云博客

本文链接：https://blog.youkuaiyun.com/lyzx_in_csdn/article/details/79677837

1、ZooKeeper中临时节点的原理是什么？

每一个ZooKeeper客户端在服务器端都对应一个session，临时节点的生命周期是session级别的，当客户端和服务端失去连接后ZooKeeper服务端中对应的session也随着消失，所以临时节点也消失

2、ZooKeeper的原生客户端中ZooKeeper对象的close方法做了哪些操作？

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/**
* Close this client object. Once the client is closed, its session becomes
* invalid. All the ephemeral nodes in the ZooKeeper server associated with
* the session will be removed. The watches left on those nodes (and on
* their parents) will be triggered.
*
* @throws InterruptedException
* /

这个是close方法的注释，大概意思是说close把客户端对应的session从服务端溢出，由这个客户端创建的临时节点也就消失了，这是Watch这个节点的监听器就可以被触发原来是关闭了

   如下所示代码 

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@Test
public void testClose2() throws InterruptedException{
    try {
        zk.close();
    } catch (InterruptedException e) {
        e.printStackTrace();
        System.err.println( "close");
    }

    try {
        zk.create( "/myF1", "".getBytes(),Ids.OPEN_ACL_UNSAFE,CreateMode.PERSISTENT);
    }catch (KeeperException | InterruptedException e) {
        System.err.println( "创建F1时失败。。。。");
        e.printStackTrace();
    }

    try {
        zk.create( "/myE1", "".getBytes(),Ids.OPEN_ACL_UNSAFE,CreateMode.EPHEMERAL);
    }catch(KeeperException | InterruptedException e) {
        System.err.println( "E1");
        e.printStackTrace();
    }
    TimeUnit.SECONDS.sleep(7);
}

会抛出异常：

   XML Code  

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org.apache.zookeeper.KeeperException$SessionExpiredException: KeeperErrorCode = Session expired for /myF1
    at org.apache.zookeeper.KeeperException.create(KeeperException.java:127)
    at org.apache.zookeeper.KeeperException.create(KeeperException.java:51)
    at org.apache.zookeeper.ZooKeeper.create(ZooKeeper.java:783)
    at com.lyzx.zk.test.crudeApi.ZkTest1.testClose2(ZkTest1.java:237)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
    at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31)
    at org.junit.runners.BlockJUnit4ClassRunner.runNotIgnored(BlockJUnit4ClassRunner.java:79)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:71)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)