[jira] [Created] (ZOOKEEPER-3803) FileTxnSnapLog.fastForwardFromEdits() throws NPE if TestingServer is started from another thread

["Vova Vysotskyi (Jira)" <ji...@apache.org>]

Vova Vysotskyi created ZOOKEEPER-3803:
-----------------------------------------

             Summary: FileTxnSnapLog.fastForwardFromEdits() throws NPE if TestingServer is started from another thread
                 Key: ZOOKEEPER-3803
                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-3803
             Project: ZooKeeper
          Issue Type: Bug
    Affects Versions: 3.4.13
            Reporter: Vova Vysotskyi


For the case when {{TestingServer.start()}} and {{TestingServer.close()}} methods are running in different threads (but {{TestingServer.close()}} is executed after {{TestingServer.start()}} is complited), {{FileTxnSnapLog.fastForwardFromEdits()}} throws NPE, since {{FileTxnSnapLog.close()}} was already called in {{TestingZooKeeperMain.internalRunFromConfig()}} method.

Such a case may be observed in unit tests when start and close methods are called in methods annotated with {{@Before}} and {{@After}} annotations.

Here is a simple test which helps to reproduce this issue:
{code:java}
  @Test
  public void testNPE() throws Exception {
    for (int i = 0; i < 100; i++) {
      TestingServer testingServer = new TestingServer();
      Thread thread = new Thread(() -> {
        try {
          testingServer.start();
        } catch (Exception e) {
          throw new RuntimeException(e);
        }
      });
      thread.start();
      thread.join();
      testingServer.close();
    }
  }
{code}

The stack trace is the following:
{noformat}
java.lang.NullPointerException
	at org.apache.zookeeper.server.persistence.FileTxnSnapLog.fastForwardFromEdits(FileTxnSnapLog.java:269)
	at org.apache.zookeeper.server.ZKDatabase.fastForwardDataBase(ZKDatabase.java:251)
	at org.apache.zookeeper.server.ZooKeeperServer.shutdown(ZooKeeperServer.java:583)
	at org.apache.zookeeper.server.ZooKeeperServer.shutdown(ZooKeeperServer.java:546)
	at org.apache.zookeeper.server.NIOServerCnxnFactory.shutdown(NIOServerCnxnFactory.java:929)
	at org.apache.curator.test.TestingZooKeeperMain.close(TestingZooKeeperMain.java:178)
	at org.apache.curator.test.TestingZooKeeperServer.stop(TestingZooKeeperServer.java:118)
	at org.apache.curator.test.TestingZooKeeperServer.close(TestingZooKeeperServer.java:130)
	at org.apache.curator.test.TestingServer.close(TestingServer.java:178)
	at org.apache.drill.exec.coord.zk.TestZookeeperClient.testNPE(TestZookeeperClient.java:109)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
	at mockit.integration.junit4.JUnit4TestRunnerDecorator.executeTestMethod(JUnit4TestRunnerDecorator.java:157)
	at mockit.integration.junit4.JUnit4TestRunnerDecorator.invokeExplosively(JUnit4TestRunnerDecorator.java:71)
	at mockit.integration.junit4.FakeFrameworkMethod.invokeExplosively(FakeFrameworkMethod.java:29)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
	at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
	at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
	at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)
{noformat}

Looks like this NPE is a regression after ZOOKEEPER-2845, where instead of using a local variable of {{txnLog}} was used class field.



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