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最近我将 (org.neo4j.driver)neo4j-java-driver从升级1.4.4到最新版本1.7.5，因为我想开始在 db 中使用时间类型。升级后一切似乎都很顺利，直到我开始使用 CLI 工具（在我的代码中准备的自定义工具），当终止时陷入无限循环：

Warning: unterminated thread Neo4jDriverIO-2-10 [23] [sun.nio.ch.EPollArrayWrapper.epollWait(Native Method), sun.nio.ch.EPollArrayWrapper.poll(EPollArrayWrapper.java:269), sun.nio.ch.EPollSelectorImpl.doSelect(EPollSelectorImpl.java:93), sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86), sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97), org.neo4j.driver.internal.shaded.io.netty.channel.nio.SelectedSelectionKeySetSelector.select(SelectedSelectionKeySetSelector.java:62), org.neo4j.driver.internal.shaded.io.netty.channel.nio.NioEventLoop.select(NioEventLoop.java:753), org.neo4j.driver.internal.shaded.io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:409), org.neo4j.driver.internal.shaded.io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:886), org.neo4j.driver.internal.shaded.io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30), java.lang.Thread.run(Thread.java:748)]
WARNING: Warning: unterminated thread Neo4jDriverIO-2-10[sun.nio.ch.EPollArrayWrapper.epollWait(Native Method), sun.nio.ch.EPollArrayWrapper.poll(EPollArrayWrapper.java:269), sun.nio.ch.EPollSelectorImpl.doSelect(EPollSelectorImpl.java:93), sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86), sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97), org.neo4j.driver.internal.shaded.io.netty.channel.nio.SelectedSelectionKeySetSelector.select(SelectedSelectionKeySetSelector.java:62), org.neo4j.driver.internal.shaded.io.netty.channel.nio.NioEventLoop.select(NioEventLoop.java:753), org.neo4j.driver.internal.shaded.io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:409), org.neo4j.driver.internal.shaded.io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:886), org.neo4j.driver.internal.shaded.io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30), java.lang.Thread.run(Thread.java:748)]
Warning: unterminated thread Neo4jDriverIO-2-9 [22] [sun.nio.ch.EPollArrayWrapper.epollWait(Native Method), sun.nio.ch.EPollArrayWrapper.poll(EPollArrayWrapper.java:269), sun.nio.ch.EPollSelectorImpl.doSelect(EPollSelectorImpl.java:93), sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86), sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97), org.neo4j.driver.internal.shaded.io.netty.channel.nio.SelectedSelectionKeySetSelector.select(SelectedSelectionKeySetSelector.java:62), org.neo4j.driver.internal.shaded.io.netty.channel.nio.NioEventLoop.select(NioEventLoop.java:753), org.neo4j.driver.internal.shaded.io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:409), org.neo4j.driver.internal.shaded.io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:886), org.neo4j.driver.internal.shaded.io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30), java.lang.Thread.run(Thread.java:748)]
WARNING: Warning: unterminated thread Neo4jDriverIO-2-9[sun.nio.ch.EPollArrayWrapper.epollWait(Native Method), sun.nio.ch.EPollArrayWrapper.poll(EPollArrayWrapper.java:269), sun.nio.ch.EPollSelectorImpl.doSelect(EPollSelectorImpl.java:93), sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86), sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97), org.neo4j.driver.internal.shaded.io.netty.channel.nio.SelectedSelectionKeySetSelector.select(SelectedSelectionKeySetSelector.java:62), org.neo4j.driver.internal.shaded.io.netty.channel.nio.NioEventLoop.select(NioEventLoop.java:753), org.neo4j.driver.internal.shaded.io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:409), org.neo4j.driver.internal.shaded.io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:886), org.neo4j.driver.internal.shaded.io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30), java.lang.Thread.run(Thread.java:748)]
[..]

在退出 CLI 程序之前，我尝试直接在驱动程序上调用 close() 方法。程序关闭时它有所帮助，但我仍然可以看到以下堆栈：

INFO: Closing driver instance 1162128198
Nov 14, 2019 5:03:25 PM org.neo4j.driver.internal.logging.JULogger info
INFO: Closing connection pool towards neo4j:7687
Warning: unterminated thread globalEventExecutor-1-2 [36] [sun.misc.Unsafe.park(Native Method), java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215), java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2078), java.util.concurrent.LinkedBlockingQueue.poll(LinkedBlockingQueue.java:467), org.neo4j.driver.internal.shaded.io.netty.util.concurrent.GlobalEventExecutor.takeTask(GlobalEventExecutor.java:92), org.neo4j.driver.internal.shaded.io.netty.util.concurrent.GlobalEventExecutor$TaskRunner.run(GlobalEventExecutor.java:245), org.neo4j.driver.internal.shaded.io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30), java.lang.Thread.run(Thread.java:748)]
WARNING: Warning: unterminated thread globalEventExecutor-1-2[sun.misc.Unsafe.park(Native Method), java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215), java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2078), java.util.concurrent.LinkedBlockingQueue.poll(LinkedBlockingQueue.java:467), org.neo4j.driver.internal.shaded.io.netty.util.concurrent.GlobalEventExecutor.takeTask(GlobalEventExecutor.java:92), org.neo4j.driver.internal.shaded.io.netty.util.concurrent.GlobalEventExecutor$TaskRunner.run(GlobalEventExecutor.java:245), org.neo4j.driver.internal.shaded.io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30), java.lang.Thread.run(Thread.java:748)]
Warning: unterminated thread globalEventExecutor-1-2 [36] [sun.misc.Unsafe.park(Native Method), java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215), java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2078), java.util.concurrent.LinkedBlockingQueue.poll(LinkedBlockingQueue.java:467), org.neo4j.driver.internal.shaded.io.netty.util.concurrent.GlobalEventExecutor.takeTask(GlobalEventExecutor.java:92), org.neo4j.driver.internal.shaded.io.netty.util.concurrent.GlobalEventExecutor$TaskRunner.run(GlobalEventExecutor.java:245), org.neo4j.driver.internal.shaded.io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30), java.lang.Thread.run(Thread.java:748)]
[..]

任何想法为什么它不能正确关闭（或者为什么它会产生网络线程？）以及为什么我看到这样的堆栈？

笔记：

  • 在 1.4.4 的情况下，当然没有观察到此类问题。
  • 我正在使用直接螺栓连接到外部单个 neo4j 数据库实例。

更新

因此，我找到了看到此类日志的原因。基本上 Neo4jDriverIO 线程现在是守护线程，我的 CLI 代码一直在检查是否有任何线程 .isDaemon 为真，并等待这些线程关闭。

在第一种情况下，它们永远不会关闭，因为来自 neo4j 驱动程序的 .close() 方法应该被 JVM 关闭钩子调用，而我们在这个 isDaemon 循环中从未上升过。

仍然是第二个问题，为什么 globalEventExecutor-1-2 在 close() 方法期间没有关闭，而是在一段时间后才关闭（这意味着它们以异步方式关闭）。这可能是一个错误，但会挖掘更多。

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