On 12/9/2013 10:01 PM, Peter Levart wrote:
On 12/09/2013 11:12 AM, Daniel Fuchs wrote:
On 12/9/13 9:58 AM, Peter Levart wrote:
On 12/09/2013 09:51 AM, Shi Jun Zhang wrote:
On 12/9/2013 4:28 PM, 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
Hi Peter,
We have thought about moving formatter out of the synchronized section
of Handler.publish(), it can avoid the deadlock. However, we can
reproduce the similar deadlock by extending the Writer in Handler and
using logger in the customized Writer.
That's right. And the remedy for that situation would also be what
Jason
Mehrens suggested - asynchronous publishing.
Hi,
I agree with Peter & Jason - asynchronous publishing seems like a good
solution. I believe the LogManager will close all handlers on exiting,
so you might want to make sure that your asynchronous handler flushes
the queue before quitting - which could still be tricky if flushing
the queue produces new log messages for the queue - and also because
you will want Handler.close() to wait until the queue is empty.
You're right, Daniel. There already is a global shut-down hook
installed in LogManager that close()s all
active handlers when VM is shutting down.
Shi Jun Zhang, here's a quick mock-up of a prototype AsyncHandler that
might work for you:
http://cr.openjdk.java.net/~plevart/misc/jul.AsyncHandler/AsyncHandler.java
Regards, Peter
Thanks Peter for your prototype. I would like to see this AsyncHandler
to be added into Java 8 or 9. However we will not use this in our stable
product as we already have several other low risk workarounds.
Anyway - the best advice still is IMHO - don't call Logger.log while
publishing a log message. This should save you from a lot of issues,
like the one you encountered - but also possible stack overflows etc...
Yes, I totally agree this, so I suggest documenting this and let other
Java developers not face this problem again.
best regards,
-- daniel
Regards, Peter
--
Regards,
Shi Jun Zhang
