IoHandlerContext Type — netty Architecture

Source Code

transport/src/main/java/io/netty/channel/IoHandlerContext.java lines 26–83

public interface IoHandlerContext {
    /**
     * Returns {@code true} if blocking for IO is allowed or if we should try to do a non-blocking request for IO to be
     * ready.
     *
     * @return {@code true} if allowed, {@code false} otherwise.
     */
    boolean canBlock();

    /**
     * Returns the amount of time left until the scheduled task with the closest deadline should run.
     *
     * @param currentTimeNanos  the current nanos.
     * @return                  nanos
     */
    long delayNanos(long currentTimeNanos);

    /**
     * Returns the absolute point in time at which the next
     * closest scheduled task should run or {@code -1} if nothing is scheduled to run.
     *
     * @return deadline.
     */
    long deadlineNanos();

    /**
     * Reports the amount of time in nanoseconds that was spent actively processing I/O events.
     * <p>
     * This metric is needed for the dynamic, utilization-based auto-scaling feature
     * in {@link MultithreadEventExecutorGroup}. The reported time
     * allows the auto-scaler to accurately measure the I/O workload of an event loop.
     * <p>
     * {@code IoHandler} implementations should measure the time spent in their event processing
     * logic and report the duration via this method. This should only include time spent
     * actively handling ready I/O events and should <strong>not</strong> include time spent blocking or
     * waiting for I/O (e.g., in an {@code epoll_wait}) call.
     * <p>
     * The default implementation of this method is a no-op. Failing to override it in an
     * {@link IoHandlerContext} that supports auto-scaling will result in the I/O utilization
     * being perceived as zero.
     *
     * @param activeNanos The duration in nanoseconds of active, non-blocking I/O work.
     */
    default void reportActiveIoTime(long activeNanos) {
        // no-op
    }

    /**
     * Returns {@code true} if the I/O handler should measure and report its active I/O time.
     * This is used as a guard to avoid the overhead of calling {@link System#nanoTime()}
     * when the feature is not in use.
     *
     * @return {@code true} if active I/O time should be reported, {@code false} otherwise.
     */
    default boolean shouldReportActiveIoTime() {
        return false;
    }
}