It sounds like your app don't block forever?
Have you taken into account that your load is not that high that the network or your
log4j socket server might be stopping your logging? If the transfer buffer is full the
socket stop returning from send till the watermark decrease!
Kind regards
Frank-Olaf Lohmann
>>> Mats Henricson <[EMAIL PROTECTED]> 13.09.2001 18.48 Uhr >>>
> > If two threads in my program logs at the same time,
> > then this function might be called in parallel.
>
> Are you sure about this? SocketAppender extends
> AppenderSkeleton, which only calls append within a
> synchronized method. This is how I believe the
> synchronization is meant to work. If you can test it
> and prove that it *is* being called in parallel,
> that would be a cause for concern.
>
> Of course, I could be entirely wrong...
I think you are right, the thread safety is guaranteed by
the synchronized doAppend() function in the AppenderSkeleton
class.
This is how our performance consultant described the problem:
It hanged for quite a while. Then it came up and later
on freezed again for sometime.
The thread dump showed that many of the threads were waiting
on org.apache.log4j.Category.callAppenders(Category.java:249).
We then removed the SocketAppender, keeping a FileAppender
attached to System.out, and a DailyRollingFileAppender. The
problems then went away.
This could be a coincidence, but we don't know that yet.
We'll try more later.
Anyway, it seems to me that the synchronization of doAppend()
is overly large. Much, if not all, of what that function
does is already thread safe:
public synchronized void doAppend(LoggingEvent event) {
if(closed) {
LogLog.error("Attempted to append to closed appender named ["+name+"].");
}
if(!isAsSevereAsThreshold(event.priority)) {
return;
}
Filter f = this.headFilter;
FILTER_LOOP:
while(f != null) {
switch(f.decide(event)) {
case Filter.DENY: return;
case Filter.ACCEPT: break FILTER_LOOP;
case Filter.NEUTRAL: f = f.next;
}
}
this.append(event);
}
This leaves the subclass append() function. For the SocketAppender
much of the code is also thread safe, I think, except for the part
described in the beginning of this email thread.
So, my current guess is that the sychronization is covering
so much code that much of our system is just waiting.
What do you all think?
Mats
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