FW: AsyncAppender revisited (was: Possible deadlock using AsyncAppender)

[Thomas Muller <tt...@online.no>]

Log4j Dev,

I've been encouraged to post this to the development list, so here it comes.

Any comments would be much appreciated.

Regards,

--

Thomas



|  -----Original Message-----
|  From: Jacob Kjome [mailto:hoju@visi.com] 
|  Sent: 24 February 2006 03:57
|  To: Log4J Users List
|  Subject: Re: AsyncAppender revisited (was: Possible deadlock 
|  using AsyncAppender)
|  
|  
|  This seems like it would get more response on the developer list.  I 
|  suggest you post it there.
|  
|  Jake
|  
|  At 09:48 AM 2/23/2006 +0000, you wrote:
|   >Log4j gurus,
|   >
|   >I can now confirm that I have a Log4j configuration where 
|  the dispatching
|   >thread (consumer) in an AsyncAppender sometimes becomes 
|  the same as the log
|   >event producer thread. This actually happens to the 
|  appender associated with
|   >the root logger, hence all threads wanting to log freeze 
|  when the buffer is
|   >full (the dispatching thread waits for the buffer to have 
|  available space,
|   >but it's only the dispatching thread that can pop from the 
|  event queue
|   >freeing up space(!)).
|   >
|   >I consider this a bug/weekness in AsyncAppender; it should 
|  check that the
|   >calling thread is different from the dispatcher thread 
|  before pushing the
|   >LoggingEvent in the append() method.
|   >
|   >public void append( LoggingEvent event ) {
|   >       if( Thread.currentThread() == dispatcher ) {
|   >               LogLog.warn( "Can't append: appending thread same as
|   >dispatcher ["
|   >                       + Thread.currentThread().getName() + "]" );
|   >               return;
|   >       }
|   >       [...]
|   >}
|   >
|   >I've written my own AsyncAppender doing the above and also 
|  refusing to log
|   >if the buffer is more than 99% log and issue a warning if 
|  the buffer is more
|   >than 95% full. Please find attached and use at your 
|  discretion. Thanks to
|   >Elijah Baley [e_baley@hotmail.com] for ideas.
|   >
|   >I've also attached the log4j.xml used in a program where 
|  the said situation
|   >arised - the root (async) appender's dispatcher became the 
|  same is the log
|   >issues causeing all logging threads to hang.
|   >
|   >Swapping the native AsyncAppender with my own 
|  XAsyncAppender fixed all the
|   >issues with our server.
|   >
|   >Any input/comments would be much appreciated.
|   >
|   >--
|   >
|   >Thomas
|   >
|   >
|   >
|   
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