[JIRA] [maven-plugin] (JENKINS-25697) Channel A with ProxyInput/OutputStream to another Channel B will hang and leak if Channel B is terminated

Thu, 20 Nov 2014 10:45:33 -0800

 
Arcadiy Ivanov edited a comment on Bug JENKINS-25697

The issue is as follows:

  1. First JNLP NIO creates a Channel A.
  2. Then AbstractMavenProcessFactory.newProcess creates a new Channel B by invoking the following: 
                Channel ch = Channels.forProcess("Channel to Maven " + Arrays.toString(cmds),
                    Computer.threadPoolForRemoting, new BufferedInputStream(con.in), new BufferedOutputStream(con.out),
                    listener.getLogger(), proc);

    The problem is, if Channel A abruptly terminates, Channel B will be stuck in all currently pending read operations (see stack traces above). The only way to terminate those read operations is to interrupt the threads that are blocked in said reads. The only way this can be achieved now is through a manual job abort (or, presumably, a Build Timeout plugin).




There is no easy or short fix for this without a major and altogether backwards-incompatible remoting rewrite. 

The problem is two-fold:



    
	
  1. Chaining channels requires upstream channels to track downstream ones. Given the current APIs and that channels are dependent on other channels via arbitrary I/O streams that are neither channel- nor dependency-aware altogether, it is virtually impossible.
    2. 
	
  2. Even if the first hurdle can be overcome, all threads blocked in IOPs have to be tracked to be interruptable asynchrnously with implementation complexity on par with Java's InterruptibleChannel.
    3.
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