如何解决代理示例trafficlock和ssl handshakelock的死锁？

时间：2012-04-18 01:33:57

标签： java netty

我结合了netty示例HexdumpProxy（http://netty.io/docs/stable/xref/org/jboss/netty/example/proxy/）和SecureChat（http://netty.io/docs）的大部分内容。 / stable / xref / org / jboss / netty / example / securechat）以形成支持SSL（和非SSL）的代理（到非SSL后端）。这似乎是个好主意，事实证明它很简单，而且正是我现在所需要的。

代理示例代码使用交通锁定锁定作为2010年报告的竞争条件的解决方案（http://markmail.org/message/x7jc6mqx6ripynqf）在饱和通道周围发生并设置传入和传出的可写和可读状态信道。

现在，在我的组合示例中，在更高的负载下，这会导致死锁，因为SSL代码中的另一个锁定“handshakelock”交织在一起。请参阅下面的探查器诊断输出。

我担心，即使在阅读了原始讨论之后，我也不明白流量锁的根本问题是否足以找到解决此死锁的直接解决方案。

（这是netty 3.2.6）

Java-level deadlock has been detected

This means that some threads are blocked waiting to enter a synchronization block or
waiting to reenter a synchronization block after an Object.wait() call, where each thread
owns one monitor while trying to obtain another monitor already held by another thread.

Deadlock:


New I/O client worker #1-2 is waiting to lock java.lang.Object@7900f3c9 which is held by New I/O server worker #1-2
New I/O server worker #1-2 is waiting to lock java.lang.Object@2d854f2f which is held by New I/O client worker #1-2




Thread stacks


New I/O client worker #1-2 [BLOCKED; waiting to lock java.lang.Object@7900f3c9]
org.jboss.netty.handler.ssl.SslHandler.wrap(SslHandler.java:665) <== sync handshakelock
org.jboss.netty.handler.ssl.SslHandler.handleDownstream(SslHandler.java:461)
org.jboss.netty.channel.DefaultChannelPipeline.sendDownstream(DefaultChannelPipeline.java:591)
org.jboss.netty.channel.DefaultChannelPipeline$DefaultChannelHandlerContext.sendDownstream(DefaultChannelPipeline.java:776)
org.jboss.netty.channel.Channels.write(Channels.java:632)
org.jboss.netty.handler.codec.oneone.OneToOneEncoder.handleDownstream(OneToOneEncoder.java:70)
org.jboss.netty.channel.DefaultChannelPipeline.sendDownstream(DefaultChannelPipeline.java:591)
org.jboss.netty.channel.DefaultChannelPipeline.sendDownstream(DefaultChannelPipeline.java:582)
org.jboss.netty.channel.Channels.write(Channels.java:611)
org.jboss.netty.channel.Channels.write(Channels.java:578)
org.jboss.netty.channel.AbstractChannel.write(AbstractChannel.java:251)
com.activevideo.frontend.ProxyInboundHandler$OutboundHandler.messageReceived(ProxyInboundHandler.java:162) <== sync trafficlock
org.jboss.netty.channel.SimpleChannelUpstreamHandler.handleUpstream(SimpleChannelUpstreamHandler.java:80)
org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream(DefaultChannelPipeline.java:564)
org.jboss.netty.channel.DefaultChannelPipeline$DefaultChannelHandlerContext.sendUpstream(DefaultChannelPipeline.java:783)
org.jboss.netty.channel.Channels.fireMessageReceived(Channels.java:302)
org.jboss.netty.handler.codec.frame.FrameDecoder.unfoldAndFireMessageReceived(FrameDecoder.java:317)
org.jboss.netty.handler.codec.frame.FrameDecoder.callDecode(FrameDecoder.java:299)
org.jboss.netty.handler.codec.frame.FrameDecoder.messageReceived(FrameDecoder.java:216)
org.jboss.netty.channel.SimpleChannelUpstreamHandler.handleUpstream(SimpleChannelUpstreamHandler.java:80)
org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream(DefaultChannelPipeline.java:564)
org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream(DefaultChannelPipeline.java:559)
org.jboss.netty.channel.Channels.fireMessageReceived(Channels.java:274)
org.jboss.netty.channel.Channels.fireMessageReceived(Channels.java:261)
org.jboss.netty.channel.socket.nio.NioWorker.read(NioWorker.java:351)
org.jboss.netty.channel.socket.nio.NioWorker.processSelectedKeys(NioWorker.java:282)
org.jboss.netty.channel.socket.nio.NioWorker.run(NioWorker.java:202)
org.jboss.netty.util.ThreadRenamingRunnable.run(ThreadRenamingRunnable.java:108)
org.jboss.netty.util.internal.DeadLockProofWorker$1.run(DeadLockProofWorker.java:44)
java.util.concurrent.ThreadPoolExecutor$Worker.runTask(unknown source)
java.util.concurrent.ThreadPoolExecutor$Worker.run(unknown source)
java.lang.Thread.run(unknown source)


New I/O server worker #1-2 [BLOCKED; waiting to lock java.lang.Object@2d854f2f]
com.activevideo.frontend.ProxyInboundHandler.channelInterestChanged(ProxyInboundHandler.java:138) <== sync trafficlock
org.jboss.netty.channel.SimpleChannelUpstreamHandler.handleUpstream(SimpleChannelUpstreamHandler.java:116)
org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream(DefaultChannelPipeline.java:564)
org.jboss.netty.channel.DefaultChannelPipeline$DefaultChannelHandlerContext.sendUpstream(DefaultChannelPipeline.java:783)
org.jboss.netty.channel.SimpleChannelUpstreamHandler.channelInterestChanged(SimpleChannelUpstreamHandler.java:192)
org.jboss.netty.channel.SimpleChannelUpstreamHandler.handleUpstream(SimpleChannelUpstreamHandler.java:116)
org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream(DefaultChannelPipeline.java:564)
org.jboss.netty.channel.DefaultChannelPipeline$DefaultChannelHandlerContext.sendUpstream(DefaultChannelPipeline.java:783)
org.jboss.netty.channel.SimpleChannelUpstreamHandler.channelInterestChanged(SimpleChannelUpstreamHandler.java:192)
org.jboss.netty.channel.SimpleChannelUpstreamHandler.handleUpstream(SimpleChannelUpstreamHandler.java:116)
org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream(DefaultChannelPipeline.java:564)
org.jboss.netty.channel.DefaultChannelPipeline$DefaultChannelHandlerContext.sendUpstream(DefaultChannelPipeline.java:783)
org.jboss.netty.channel.SimpleChannelUpstreamHandler.channelInterestChanged(SimpleChannelUpstreamHandler.java:192)
org.jboss.netty.channel.SimpleChannelUpstreamHandler.handleUpstream(SimpleChannelUpstreamHandler.java:116)
org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream(DefaultChannelPipeline.java:564)
org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream(DefaultChannelPipeline.java:559)
org.jboss.netty.channel.Channels.fireChannelInterestChanged(Channels.java:335)
org.jboss.netty.channel.socket.nio.NioWorker.setInterestOps(NioWorker.java:728)
org.jboss.netty.channel.socket.nio.NioServerSocketPipelineSink.handleAcceptedSocket(NioServerSocketPipelineSink.java:129)
org.jboss.netty.channel.socket.nio.NioServerSocketPipelineSink.eventSunk(NioServerSocketPipelineSink.java:76)
org.jboss.netty.channel.DefaultChannelPipeline$DefaultChannelHandlerContext.sendDownstream(DefaultChannelPipeline.java:771)
org.jboss.netty.handler.ssl.SslHandler.handleDownstream(SslHandler.java:430)
org.jboss.netty.channel.DefaultChannelPipeline.sendDownstream(DefaultChannelPipeline.java:591)
org.jboss.netty.channel.DefaultChannelPipeline$DefaultChannelHandlerContext.sendDownstream(DefaultChannelPipeline.java:776)
org.jboss.netty.handler.codec.oneone.OneToOneEncoder.handleDownstream(OneToOneEncoder.java:60)
org.jboss.netty.channel.DefaultChannelPipeline.sendDownstream(DefaultChannelPipeline.java:591)
org.jboss.netty.channel.DefaultChannelPipeline.sendDownstream(DefaultChannelPipeline.java:582)
org.jboss.netty.channel.Channels.setInterestOps(Channels.java:652)
org.jboss.netty.channel.AbstractChannel.setInterestOps(AbstractChannel.java:222)
org.jboss.netty.channel.AbstractChannel.setReadable(AbstractChannel.java:244)
com.activevideo.frontend.SSLProxyInboundHandler$BackendConnector$1.operationComplete(SSLProxyInboundHandler.java:92)
org.jboss.netty.channel.DefaultChannelFuture.notifyListener(DefaultChannelFuture.java:381)
org.jboss.netty.channel.DefaultChannelFuture.addListener(DefaultChannelFuture.java:148)
com.activevideo.frontend.SSLProxyInboundHandler$BackendConnector.operationComplete(SSLProxyInboundHandler.java:87)
org.jboss.netty.channel.DefaultChannelFuture.notifyListener(DefaultChannelFuture.java:381)
org.jboss.netty.channel.DefaultChannelFuture.notifyListeners(DefaultChannelFuture.java:367)
org.jboss.netty.channel.DefaultChannelFuture.setSuccess(DefaultChannelFuture.java:316)
org.jboss.netty.handler.ssl.SslHandler.setHandshakeSuccess(SslHandler.java:1040)
org.jboss.netty.handler.ssl.SslHandler.wrapNonAppData(SslHandler.java:838)
org.jboss.netty.handler.ssl.SslHandler.unwrap(SslHandler.java:907)    <=== sync handshakelock
org.jboss.netty.handler.ssl.SslHandler.decode(SslHandler.java:620)
org.jboss.netty.handler.codec.frame.FrameDecoder.callDecode(FrameDecoder.java:282)
org.jboss.netty.handler.codec.frame.FrameDecoder.messageReceived(FrameDecoder.java:214)
org.jboss.netty.channel.SimpleChannelUpstreamHandler.handleUpstream(SimpleChannelUpstreamHandler.java:80)
org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream(DefaultChannelPipeline.java:564)
org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream(DefaultChannelPipeline.java:559)
org.jboss.netty.channel.Channels.fireMessageReceived(Channels.java:274)
org.jboss.netty.channel.Channels.fireMessageReceived(Channels.java:261)
org.jboss.netty.channel.socket.nio.NioWorker.read(NioWorker.java:351)
org.jboss.netty.channel.socket.nio.NioWorker.processSelectedKeys(NioWorker.java:282)
org.jboss.netty.channel.socket.nio.NioWorker.run(NioWorker.java:202)
org.jboss.netty.util.ThreadRenamingRunnable.run(ThreadRenamingRunnable.java:108)
org.jboss.netty.util.internal.DeadLockProofWorker$1.run(DeadLockProofWorker.java:44)
java.util.concurrent.ThreadPoolExecutor$Worker.runTask(unknown source)
java.util.concurrent.ThreadPoolExecutor$Worker.run(unknown source)
java.lang.Thread.run(unknown source)

1 个答案:

答案 0 :(得分：1)

好的，我想我修好了。

Proxy示例中早期竞争条件的解决方案不必要地包括对synchronized块中的write（）的调用。

原始问题是在传出线程（TO）和传入线程（TI）之间存在这种（罕见）竞争条件：

  1. TO：inboundChannel.write（）（在messageReceived）
  2. TO：inboundChannel.isWritable（）返回false（在messageReceived处）
  3. 然后刷新在（1）发出的待处理写入
  4. TI：inboundChannel.isWritable（）返回true（在channelInterestChanged处）
  5. TI：outboundChannel.setReadable（true）（在channelInterestChanged处）
  6. TO：outboundChannel.setReadable（false）（在messageReceived处）

    7. 2010年的解决方案是在inboundChannel和outboundChannel（以及在InterestChanged处理程序）的messageReceived（）处理程序中引入同步（使用'trafficlock'），如下所示：

    synchronized (trafficLock) {
  outboundChannel.write(msg);
  // If outboundChannel is saturated, do not read until notified in
  // OutboundHandler.channelInterestChanged().
  if (!outboundChannel.isWritable()) {
    e.getChannel().setReadable(false);
  }
}

    这确实解决了竞争条件，因为您阻止步骤3,4和5干扰步骤2和6.但是，将步骤1（write（））从同步块中移出是安全的。 / p>

    对write（）的调用导致死锁，因为在SSLHandler中调用该调用，它使用另一个锁定handskkock。

    所以..我将调用移到了两个位置的synchronized块之外的write（）。僵局现在消失了。我建议相应更改“官方”代理示例。

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