ImmediateEventExecutor Class — netty Architecture

Source Code

common/src/main/java/io/netty/util/concurrent/ImmediateEventExecutor.java lines 33–161

public final class ImmediateEventExecutor extends AbstractEventExecutor {
    private static final InternalLogger logger = InternalLoggerFactory.getInstance(ImmediateEventExecutor.class);
    public static final ImmediateEventExecutor INSTANCE = new ImmediateEventExecutor();
    /**
     * A Runnable will be queued if we are executing a Runnable. This is to prevent a {@link StackOverflowError}.
     */
    private static final FastThreadLocal<Queue<Runnable>> DELAYED_RUNNABLES = new FastThreadLocal<Queue<Runnable>>() {
        @Override
        protected Queue<Runnable> initialValue() throws Exception {
            return new ArrayDeque<Runnable>();
        }
    };
    /**
     * Set to {@code true} if we are executing a runnable.
     */
    private static final FastThreadLocal<Boolean> RUNNING = new FastThreadLocal<Boolean>() {
        @Override
        protected Boolean initialValue() throws Exception {
            return false;
        }
    };

    private final Future<?> terminationFuture = new FailedFuture<Object>(
            GlobalEventExecutor.INSTANCE, new UnsupportedOperationException());

    private ImmediateEventExecutor() { }

    @Override
    public boolean inEventLoop() {
        return true;
    }

    @Override
    public boolean inEventLoop(Thread thread) {
        return true;
    }

    @Override
    public Future<?> shutdownGracefully(long quietPeriod, long timeout, TimeUnit unit) {
        return terminationFuture();
    }

    @Override
    public Future<?> terminationFuture() {
        return terminationFuture;
    }

    @Override
    @Deprecated
    public void shutdown() { }

    @Override
    public boolean isShuttingDown() {
        return false;
    }

    @Override
    public boolean isShutdown() {
        return false;
    }

    @Override
    public boolean isTerminated() {
        return false;
    }

    @Override
    public boolean awaitTermination(long timeout, TimeUnit unit) {
        return false;
    }

    @Override
    public void execute(Runnable command) {
        ObjectUtil.checkNotNull(command, "command");
        if (!RUNNING.get()) {
            RUNNING.set(true);
            try {
                command.run();
            } catch (Throwable cause) {
                logger.info("Throwable caught while executing Runnable {}", command, cause);
            } finally {