1 EventExecutorChooser

一个接口，用于选择下一个EventExecutor

2 EventExecutorChooserFactory

一个接口，语义是工厂，一个生产EventExecutorChooser的工厂

3 netty中EventExecutorChooser的默认实现GenericEventExecutorChooser

GenericEventExecutorChooser中存放了一个EventExecutor的数组，你调用next，它会一直做轮询，到尾部元素了，就从头部元素接着在来；

private static final class GenericEventExecutorChooser implements EventExecutorChooser {
    // Use a 'long' counter to avoid non-round-robin behaviour at the 32-bit overflow boundary.
    // The 64-bit long solves this by placing the overflow so far into the future, that no system
    // will encounter this in practice.
    private final AtomicLong idx = new AtomicLong();
    private final EventExecutor[] executors;

    GenericEventExecutorChooser(EventExecutor[] executors) {
        this.executors = executors;
    }

    @Override
    public EventExecutor next() {
        return executors[(int) Math.abs(idx.getAndIncrement() % executors.length)];
    }
}

4 netty中EventExecutorChooser的默认实现PowerOfTwoEventExecutorChooser

PowerOfTwoEventExecutorChooser中存放了一个EventExecutor的数组，如果EventExecutor数组的大小是2的几次幂，你调用next，它会一直做轮询，到尾部元素了，就从头部元素接着在来；

private static final class PowerOfTwoEventExecutorChooser implements EventExecutorChooser {
    private final AtomicInteger idx = new AtomicInteger();
    private final EventExecutor[] executors;

    PowerOfTwoEventExecutorChooser(EventExecutor[] executors) {
        this.executors = executors;
    }

    @Override
    public EventExecutor next() {
        return executors[idx.getAndIncrement() & executors.length - 1];
    }
}

5 EventExecutorChooserFactory的默认实现DefaultEventExecutorChooserFactory

newChooser方法的实现，如果EventExecutor[] executors的大小是2的幂次，则new PowerOfTwoEventExecutorChooser否则new GenericEventExecutorChooser；

@Override
public EventExecutorChooser newChooser(EventExecutor[] executors) {
    if (isPowerOfTwo(executors.length)) {
        return new PowerOfTwoEventExecutorChooser(executors);
    } else {
        return new GenericEventExecutorChooser(executors);
    }
}