EpollIoHandler Class — netty Architecture

Source Code

transport-classes-epoll/src/main/java/io/netty/channel/epoll/EpollIoHandler.java lines 54–575

public class EpollIoHandler implements IoHandler {
    private static final InternalLogger logger = InternalLoggerFactory.getInstance(EpollIoHandler.class);
    private static final long EPOLL_WAIT_MILLIS_THRESHOLD =
            SystemPropertyUtil.getLong("io.netty.channel.epoll.epollWaitThreshold", 10);

    {
        Epoll.ensureAvailability();
    }

    // Pick a number that no task could have previously used.
    private long prevDeadlineNanos = NONE;
    private FileDescriptor epollFd;
    private FileDescriptor eventFd;
    private FileDescriptor timerFd;
    private final IntObjectMap<DefaultEpollIoRegistration> registrations = new IntObjectHashMap<>(4096);
    private final boolean allowGrowing;
    private final EpollEventArray events;
    private final NativeArrays nativeArrays;

    private final SelectStrategy selectStrategy;
    private final IntSupplier selectNowSupplier = new IntSupplier() {
        @Override
        public int get() throws Exception {
            return epollWaitNow();
        }
    };
    private final ThreadAwareExecutor executor;

    private static final long AWAKE = -1L;
    private static final long NONE = Long.MAX_VALUE;

    // nextWakeupNanos is:
    //    AWAKE            when EL is awake
    //    NONE             when EL is waiting with no wakeup scheduled
    //    other value T    when EL is waiting with wakeup scheduled at time T
    private final AtomicLong nextWakeupNanos = new AtomicLong(AWAKE);
    private boolean pendingWakeup;

    private int numChannels;

    // See https://man7.org/linux/man-pages/man2/timerfd_create.2.html.
    private static final long MAX_SCHEDULED_TIMERFD_NS = 999999999;

    /**
     * Returns a new {@link IoHandlerFactory} that creates {@link EpollIoHandler} instances.
     */
    public static IoHandlerFactory newFactory() {
        return newFactory(0, DefaultSelectStrategyFactory.INSTANCE);
    }

    /**
     * Returns a new {@link IoHandlerFactory} that creates {@link EpollIoHandler} instances.
     */
    public static IoHandlerFactory newFactory(final int maxEvents,
                                              final SelectStrategyFactory selectStrategyFactory) {
        Epoll.ensureAvailability();
        ObjectUtil.checkPositiveOrZero(maxEvents, "maxEvents");
        ObjectUtil.checkNotNull(selectStrategyFactory, "selectStrategyFactory");
        return new IoHandlerFactory() {
            @Override
            public IoHandler newHandler(ThreadAwareExecutor executor) {
                return new EpollIoHandler(executor, maxEvents, selectStrategyFactory.newSelectStrategy());
            }

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

    // Package-private for testing
    EpollIoHandler(ThreadAwareExecutor executor, int maxEvents, SelectStrategy strategy) {
        this.executor = ObjectUtil.checkNotNull(executor, "executor");
        selectStrategy = ObjectUtil.checkNotNull(strategy, "strategy");
        if (maxEvents == 0) {
            allowGrowing = true;
            events = new EpollEventArray(4096);
        } else {
            allowGrowing = false;
            events = new EpollEventArray(maxEvents);