Deadlock between FileHandler and ConsoleHandler when using customized formatter

Peter Levart peter.levart at
Mon Dec 9 08:40:15 UTC 2013

On 12/09/2013 09:28 AM, Peter Levart wrote:
> On 12/09/2013 08:02 AM, Shi Jun Zhang wrote:
>> Peter,
>> I think you are misunderstanding this problem. This deadlock is not 
>> related to the formatter synchronization, we can make 
>> CustomerFormatter.format not synchronized and not call super.format, 
>> the deadlock still happens.
> I'm not saying that your formatters are explicitly synchronized - all 
> formatters are currently effectively synchronized by LogHandlers. The 
> Formatter is invoked from within LogHandler's publish() method which 
> is synchronized (on LogHandler.this). If formatters were invoked out 
> of this synchronized section, there would be no danger of deadlocks 
> when using Logger.log from within custom formatters. But then other 
> issues would arise as a consequence of non-multithreaded formatters 
> being invoked concurrently...
> Regards, Peter

I think the best solution to your problem (or a work-around if you say 
so) was suggested by Jason Mehrens few messages ago - decoupling of user 
code from publishing of log records - by creating an AsyncLogHandler 
that is just feeding a FIFO queue with log records which are processed 
by a background thread by pop-ing them out of queue and sticking them in 
the actual LogHandler.publish(). If the queue is unbouded or large 
enough so that it never fills up, there's no danger of dead-locks even 
if you invoke Logger.log from custom formatters in such background 
publishing thread.

Regards, Peter

More information about the core-libs-dev mailing list