LoggerConfig improvement

[Remko Popma]

I want to run this by you:

LoggerConfig currently always takes a lock after logging a log event.
Within this lock it checks if the shutdown flag has been set.
Can we do it the other way around? First check if the shutdown flag has
been set and then take the lock (to notify the other thread)?

I think it is safe to do this:

public void log(final LogEvent event) {
    counter.incrementAndGet();
    try {
        if (!isFiltered(event)) {
            processLogEvent(event);
        }
    } finally {
        // FIRST update counter, THEN check shutdown flag;
        // these are atomic and will not get re-ordered.
        // So we don't need the lock to check the shutdown flag.
        if (counter.decrementAndGet() == 0 && shutdown.get()) {
            // ONLY take the lock if the shutdown flag was set
            shutdownLock.lock();
            try {
                noLogEvents.signalAll(); // lock required to call signal()
            } finally {
                shutdownLock.unlock();
            }
        }
    }
}

// keep this method unchanged
private void waitForCompletion() {
    shutdownLock.lock();
    try {
        // NOTE: FIRST the shutdown flag is set
        if (shutdown.compareAndSet(false, true)) {
            int retries = 0;
            // NOTE: THEN the counter is read
            while (counter.get() > 0) {
                try {
                    noLogEvents.await(retries + 1, TimeUnit.SECONDS);
                } catch (final InterruptedException ie) {
                    if (++retries > MAX_RETRIES) {
                        break;
                    }
                }
            }
        }
    } finally {
        shutdownLock.unlock();
    }
}