Hi guys,
Please don't take this as bad criticism. I'm just trying to provide
some *useful* insights. And besides, I think you guys are doing a great
job on log4j.
I just read on the internet how log4j uses synchronized methods
everywhere. I'm not too sure if it's true or not. But, a grep of the
source shows me one place where it uses a synchronized method when it
shouldn't.
It's located in LF5Appender.
protected static synchronized LogBrokerMonitor getDefaultInstance() {
if (_defaultLogMonitor == null) {
try {
_defaultLogMonitor =
new LogBrokerMonitor(LogLevel.getLog4JLevels());
_finalizer = new AppenderFinalizer(_defaultLogMonitor);
_defaultLogMonitor.setFrameSize(getDefaultMonitorWidth(),
getDefaultMonitorHeight());
_defaultLogMonitor.setFontSize(12);
_defaultLogMonitor.show();
} catch (SecurityException e) {
_defaultLogMonitor = null;
}
}
return _defaultLogMonitor;
}
As a general rule, singleton methods should not be synchronized for
performance reasons. If this method is only called once in awhile, no
big deal. But, if it's called regularly, then it can be a really big
performance problem. Does the log4j project have coding standards for
such things?
This particular singleton method should check the "_defaultLogMonitor"
for null first. If it is not null, it should return it. If it is null,
it should synchronize on some object, perhaps LF5Appender.class. Then
it should check it for null again. If it is not null, it should return
it. If it is null, it should construct it.
Code from one of my singletons is below. This code is guaranteed to be
thread safe, as well as be very high performing if it was called
multiple times from different threads.
if (commandFactory == null)
{
synchronized (CommandFactory.class)
{
if (commandFactory == null)
{
try
{
commandFactory = new CommandFactory();
}
catch (Exception exception)
{
logger.info("error loading CommandFactory",
exception);
}
}
}
}
return commandFactory;
I hope that helps.
--
Trenton D. Adams
Systems Analyst/Web Software Engineer
Navy Penguins at your service!
Athabasca University
(780) 675-6195
:wq!
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