尝试关闭 mongoclient 时线程被阻塞

Question

我有一个使用多个数据库的应用程序，因此我创建多个连接并将它们保存在并发哈希图中。

如果连接不存在，我只需创建一个新连接并将其放入该映射中，如果该任务完成，我们将关闭并删除一些客户端。

经过多轮创建-关闭-删除操作后，关闭某些客户端时发生异常，表示线程已被阻塞。

为什么要关闭一个 mongo 客户端并在很长一段时间内导致线程阻塞，我怎样才能避免这个问题的发生？

谢谢！

Vertx版本：4.2.3

Java版本：1.8.0_201

02:10:05.626 WARN i.v.core.impl.BlockedThreadChecker - Thread Thread[vert.x-eventloop-thread-27,5,main] has been blocked for 5058 ms, time limit is 2000 ms
io.vertx.core.VertxException: Thread blocked
at sun.misc.Unsafe.park(Native Method)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(AbstractQueuedSynchronizer.java:997)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1304)
at java.util.concurrent.CountDownLatch.await(CountDownLatch.java:231)
at com.mongodb.internal.connection.AsynchronousChannelStream$FutureAsyncCompletionHandler.get(AsynchronousChannelStream.java:317)
at com.mongodb.internal.connection.AsynchronousChannelStream$FutureAsyncCompletionHandler.getRead(AsynchronousChannelStream.java:312)
at com.mongodb.internal.connection.AsynchronousChannelStream.read(AsynchronousChannelStream.java:151)
at com.mongodb.internal.connection.InternalStreamConnection.receiveResponseBuffers(InternalStreamConnection.java:648)
at com.mongodb.internal.connection.InternalStreamConnection.receiveMessageWithAdditionalTimeout(InternalStreamConnection.java:513)
at com.mongodb.internal.connection.InternalStreamConnection.receiveCommandMessageResponse(InternalStreamConnection.java:356)
at com.mongodb.internal.connection.InternalStreamConnection.sendAndReceive(InternalStreamConnection.java:280)
at com.mongodb.internal.connection.CommandHelper.sendAndReceive(CommandHelper.java:83)
at com.mongodb.internal.connection.CommandHelper.executeCommand(CommandHelper.java:33)
at com.mongodb.internal.connection.InternalStreamConnectionInitializer.initializeConnectionDescription(InternalStreamConnectionInitializer.java:107)
at com.mongodb.internal.connection.InternalStreamConnectionInitializer.initialize(InternalStreamConnectionInitializer.java:62)
at com.mongodb.internal.connection.InternalStreamConnection.open(InternalStreamConnection.java:144)
at com.mongodb.internal.connection.UsageTrackingInternalConnection.open(UsageTrackingInternalConnection.java:51)
at com.mongodb.internal.connection.DefaultConnectionPool$PooledConnection.open(DefaultConnectionPool.java:431)
at com.mongodb.internal.connection.DefaultConnectionPool.get(DefaultConnectionPool.java:115)
at com.mongodb.internal.connection.DefaultConnectionPool.get(DefaultConnectionPool.java:100)
at com.mongodb.internal.connection.DefaultServer.getConnection(DefaultServer.java:92)
at com.mongodb.internal.session.ServerSessionPool.endClosedSessions(ServerSessionPool.java:156)
at com.mongodb.internal.session.ServerSessionPool.close(ServerSessionPool.java:103)
at com.mongodb.internal.async.client.AsyncMongoClientImpl.close(AsyncMongoClientImpl.java:119)
at com.mongodb.reactivestreams.client.internal.MongoClientImpl.close(MongoClientImpl.java:65)
at io.vertx.ext.mongo.impl.MongoClientImpl$MongoHolder.close(MongoClientImpl.java:1283)
at io.vertx.ext.mongo.impl.MongoClientImpl.close(MongoClientImpl.java:132)
at io.vertx.ext.mongo.impl.MongoClientImpl.close(MongoClientImpl.java:1243)
at io.vertx.reactivex.ext.mongo.MongoClient.close(MongoClient.java:1921)
at io.vertx.reactivex.ext.mongo.MongoClient.close(MongoClient.java:1928)