Logkit: Possible 'deadlock' in AsyncLogTarget ...

[Michael Bachran <mb...@voiceobjects.com>]

Hi,

Sorry for disturbing the release process of LogKit :-).
But there is a possible 'deadlock' in doProcessEvent() of AsyncLogTarget.

When waiting in case of a full queue ...

(AsynLogTarget:131)

		final int size = m_list.size();
            while( m_queueSize <= size )
            {
                try
                {
                    m_list.wait();
                }
                catch( final InterruptedException ie )
                {
                    //This really should not occur ...
                    //Maybe we should log it though for
                    //now lets ignore it
                }
            }

... we do not recalculate the size. Therefore any thread waiting for the queue to get a free slot
will not recognize when an element is removed.

This means all threads of a system that are logging to that target might block here forever 
(if the consumer is to slow or the queue to small).

I would recommend to patch like this:

-		final int size = m_list.size();
+		int size = m_list.size();
            while( m_queueSize <= size )
            {
                try
                {
                    m_list.wait();
                }
                catch( final InterruptedException ie )
                {
                    //This really should not occur ...
                    //Maybe we should log it though for
                    //now lets ignore it
                }
+                size = m_list.size();
            }

(... or use the size() function directly for comparison).


Additionally I got an issue when restarting my system (including complete reestablishment of the log-system without closing the JVM) 
because the AsyncTargets are not closing the targets they are wrapping and when restarting opening a stream to 
an underlying file-target will not get the required write-access.
I somehow hacked it like this (close() cannot be called from the interface LogTarget):

(AsynLogTarget:192)

			  else if( interupted || Thread.interrupted() )
                    {
                        //ie there is nothing in queue and thread is interrupted
                        //thus we stop thread

+                        try
+                        {
+                            if ( m_logTarget instanceof AbstractTarget )
+                            {
+                                ((AbstractTarget)m_logTarget).close();
+                            }
+                        }
+                        catch( final Throwable throwable )
+                        {
+                            getErrorHandler().error( "Unknown error closing target.", throwable, event );
+                        }

                        return;
                    }


Michael

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RE: Logkit: Possible 'deadlock' in AsyncLogTarget ...

[Leo Sutic <le...@inspireinfrastructure.com>]

> From: Michael Bachran [mailto:mbachran@voiceobjects.com] 
> 
> Hi,
> 
> Sorry for disturbing the release process of LogKit :-).

Don't worry, we'll get this patch into 1.2.1.

/LS



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