[GitHub] [pulsar] jerrypeng opened a new pull request #5731: fix potential deadlock in pulsar client close

[GitBox <gi...@apache.org>]

jerrypeng opened a new pull request #5731: fix potential deadlock in pulsar client close
URL: https://github.com/apache/pulsar/pull/5731
 
 
   # Motivation
   
   A deadlock on PulsarClient.close() can happen if there are producers/consumers that are not closed prior to calling PulsarClient.close() and we have to close them in the routine.  The deadlock happens be cause we piggy pack off of a "pulsar-io" thread that is used to shutdown the connection in producer/consumer close, to also shutdown the EventLoopGroup.  "pulsar-io" thread is part of the EventLoopGroup thus it tries to shutdown itself and causes a deadlock.  
   
   Below is a stacktrace of what it look like:
   
   ```
   "pulsar-client-io-1-1" #20 prio=5 os_prio=31 tid=0x00007fc312a78800 nid=0x9a03 in Object.wait() [0x000070000384e000]
      java.lang.Thread.State: WAITING (on object monitor)
       at java.lang.Object.wait(Native Method)
       - waiting on <0x00000007b8532640> (a io.netty.util.concurrent.DefaultPromise)
       at java.lang.Object.wait(Object.java:502)
       at io.netty.util.concurrent.DefaultPromise.await(DefaultPromise.java:252)
       - locked <0x00000007b8532640> (a io.netty.util.concurrent.DefaultPromise)
       at io.netty.util.concurrent.DefaultPromise.sync(DefaultPromise.java:403)
       at io.netty.util.concurrent.DefaultPromise.sync(DefaultPromise.java:35)
       at org.apache.pulsar.client.impl.ConnectionPool.close(ConnectionPool.java:286)
       at org.apache.pulsar.client.impl.PulsarClientImpl.shutdown(PulsarClientImpl.java:578)
       at org.apache.pulsar.client.impl.PulsarClientImpl.lambda$closeAsync$18(PulsarClientImpl.java:560)
       at org.apache.pulsar.client.impl.PulsarClientImpl$$Lambda$82/878861517.run(Unknown Source)
       at java.util.concurrent.CompletableFuture.uniRun(CompletableFuture.java:705)
       at java.util.concurrent.CompletableFuture$UniRun.tryFire(CompletableFuture.java:687)
       at java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:474)
       at java.util.concurrent.CompletableFuture.complete(CompletableFuture.java:1962)
       at org.apache.pulsar.client.impl.ProducerImpl.lambda$closeAsync$9(ProducerImpl.java:735)
       at org.apache.pulsar.client.impl.ProducerImpl$$Lambda$80/1123226989.apply(Unknown Source)
       at java.util.concurrent.CompletableFuture.uniHandle(CompletableFuture.java:822)
       at java.util.concurrent.CompletableFuture$UniHandle.tryFire(CompletableFuture.java:797)
       at java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:474)
       at java.util.concurrent.CompletableFuture.complete(CompletableFuture.java:1962)
       at org.apache.pulsar.client.impl.ClientCnx.handleSuccess(ClientCnx.java:406)
       at org.apache.pulsar.common.protocol.PulsarDecoder.channelRead(PulsarDecoder.java:222)
       at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374)
       at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360)
       at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:352)
       at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:326)
       at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:300)
       at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374)
       at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360)
       at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:352)
       at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1422)
       at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374)
       at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360)
       at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:931)
       at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:163)
       at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:700)
       at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:635)
       at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:552)
       at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:514)
       at io.netty.util.concurrent.SingleThreadEventExecutor$6.run(SingleThreadEventExecutor.java:1050)
       at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
       at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
       at java.lang.Thread.run(Thread.java:748)
   ```
   
   This deadlock went unnoticed for a long time because in the past we never waited for the shutdown of the EventLoopGroup to complete
   
   Also #5628 does not solve the issue.  This PR should supersede that one.
   
   

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