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From "Sebb (JIRA)" <j...@apache.org>
Subject [jira] Resolved: (NET-348) Queue is full TelnetInputStream
Date Thu, 03 Mar 2011 13:47:37 GMT

     [ https://issues.apache.org/jira/browse/NET-348?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Sebb resolved NET-348.
----------------------

    Resolution: Fixed

Thanks for the report.

Fixed by moving the "__threaded = true;" statement to the thread run() method, so it will
be set when the thread actually starts.

> Queue is full TelnetInputStream
> -------------------------------
>
>                 Key: NET-348
>                 URL: https://issues.apache.org/jira/browse/NET-348
>             Project: Commons Net
>          Issue Type: Bug
>          Components: Telnet
>    Affects Versions: 1.4
>         Environment: Windows XP, Java JRE 1.6 
>            Reporter: Krishnan Sivaramakrishna Iyer
>
> Hello 
>   I am using Telnet library of common.net. And I got an exception 
> in TelnetInputStream once in a while. 
>  
> The exception message was as following.
> ------------------------------------------------------------------------
> --------------------------------------------
> Exception in thread "Thread-9399" java.lang.IllegalStateException: Queue
> is full! Cannot process another character.
>         at
> org.apache.commons.net.telnet.TelnetInputStream.__processChar(TelnetInpu
> tStream.java:306)
>         at
> org.apache.commons.net.telnet.TelnetInputStream.run(TelnetInputStream.ja
> va:596)
>         at java.lang.Thread.run(Thread.java:619)
> ------------------------------------------------------------------------
> --------------------------------------------
>  
> At first, I think it is possible that I didn't call read() in time to
> read the data in TelnetInputStream so that the buffer
> of TelnetInputStream overflowed. But then I wrote a simple program to
> test it and I found that it is not the cause.
>  
> Then I studied the source of TelnetInputStream. The segment of function
> __processChar is as following.
> 280
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#280>      private void __processChar(int ch) throws
> InterruptedException
> 281
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#281>      {
> 282
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#282>          // Critical section because we're
> altering __bytesAvailable,
> 283
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#283>          // __queueTail, and the contents of
> _queue.
> 284
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#284>          synchronized (__queue)
> 285
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#285>          {
> 286
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#286>              while (__bytesAvailable >=
> __queue.length - 1)
> 287
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#287>              {
> 288
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#288>                  // The queue is full. We need to
> wait before adding any more data to it. Hopefully the stream owner
> 289
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#289>                  // will consume some data soon! 
> 290
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#290>                  if(__threaded)
> 291
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#291>                  {
> 292
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#292>                      __queue.notify();
> 293
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#293>                      try
> 294
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#294>                      {
> 295
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#295>                          __queue.wait();
> 296
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#296>                      }
> 297
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#297>                      catch (InterruptedException
> e)
> 298
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#298>                      {
> 299
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#299>                          throw e;
> 300
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#300>                      }
> 301
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#301>                  }
> 302
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#302>                  else
> 303
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#303>                  {
> 304
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#304>                      // We've been asked to add
> another character to the queue, but it is already full and there's
> 305
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#305>                      // no other thread to drain
> it. This should not have happened! 
> 306
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#306>                      throw new
> IllegalStateException("Queue is full! Cannot process another
> character.");
> 307
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#307>                  }
> 308
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#308>              }
> 309
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#309>  
> 310
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#310>              // Need to do this in case we're not
> full, but block on a read
> 311
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#311>              if (__readIsWaiting && __threaded)
> 312
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#312>              {
> 313
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#313>                  __queue.notify();
> 314
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#314>              }
> 315
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#315>  
> 316
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#316>              __queue[__queueTail] = ch;
> 317
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#317>              ++__bytesAvailable;
> 318
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#318>  
> 319
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#319>              if (++__queueTail >= __queue.length)
> 320
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#320>                  __queueTail = 0;
> 321
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#321>          }
> 322
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#322>      }
>  
> In line 306 the exception IllegalStateException is thrown. In this
> condition, the variable __threaded should be false.
> But I didn't call TelnetClient.setReaderThread
> <http://commons.apache.org/net/api/org/apache/commons/net/telnet/TelnetC
> lient.html#setReaderThread%28boolean%29>  to set it to false.
>  
> The __threaded is set to true in _start() of TelnetInputStream
> 84
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#84>       void _start()
> 85
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#85>       {
> 86
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#86>           if(__thread == null)
> 87
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#87>               return;
> 88
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#88>   
> 89
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#89>           int priority;
> 90
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#90>           __isClosed = false;
> 91
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#91>           // TODO remove this
> 92
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#92>           // Need to set a higher priority in case
> JVM does not use pre-emptive
> 93
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#93>           // threads.  This should prevent
> scheduler induced deadlock (rather than
> 94
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#94>           // deadlock caused by a bug in this
> code).
> 95
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#95>           priority =
> Thread.currentThread().getPriority() + 1;
> 96
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#96>           if (priority > Thread.MAX_PRIORITY)
> 97
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#97>               priority = Thread.MAX_PRIORITY;
> 98
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#98>           __thread.setPriority(priority);
> 99
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#99>           __thread.setDaemon(true);
> 100
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#100>          __thread.start();
> 101
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#101>          __threaded = true;
> 102
> <http://commons.apache.org/net/xref/org/apache/commons/net/telnet/Telnet
> InputStream.html#102>      }
>  
> I guess that is there a possibility that the thread in __thread.start()
> is started so fast that when __processChar() is called, the __threaded
> has not been set to true.
> So the exception IllegalStateException is thrown.
> I think line 101 should be moved up of line 100.

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