DefaultAccessLogReceiver cannot always be closed cleanly and may log a NullPointerException

These two tests should hopefully illustrate the problem: @Test public void cleanShutdownAfterLoggingAMessage() throws IOException, InterruptedException { Xnio xnio = Xnio.getInstance(getClass().getClassLoader()); XnioWorker worker = xnio.createWorker(OptionMap.builder().getMap()); File outputDirectory = new File("target/access_logs"); outputDirectory.mkdirs(); DefaultAccessLogReceiver receiver = new DefaultAccessLogReceiver(worker, outputDirectory, "foo."); // This will work because logging the message causes the writer to be created. receiver.logMessage("message"); // Sleep for a bit so that the writer gets created before we close the receiver Thread.sleep(100); receiver.close(); // Sleep for a bit to give any exception a chance to occur Thread.sleep(100); } @Test public void cleanShutdownWithAFreshReceiver() throws IOException, InterruptedException { Xnio xnio = Xnio.getInstance(getClass().getClassLoader()); XnioWorker worker = xnio.createWorker(OptionMap.builder().getMap()); File outputDirectory = new File("target/access_logs"); outputDirectory.mkdirs(); DefaultAccessLogReceiver receiver = new DefaultAccessLogReceiver(worker, outputDirectory, "foo."); // This will NPE because the receiver's writer is null. This can happen if the // receiver isn't used before it's closed, or it's closed after it's been rotated. receiver.close(); // Sleep for a bit to give any exception a chance to occur Thread.sleep(100); } The first test will not log any exception due to the logging of the message creating the writer. The second test will log an NPE because the writer is null.