int acquisitionStartIndex(int need) {
        for (;;) {
            final int current = acquisitionStartIndex;
            final int next = (current + need) % eventLoops.size();
            if (acquisitionStartIndexUpdater.compareAndSet(this, current, next)) {
                return current;
            }
        }
    }
Returns the index of {@link #eventLoops} which an {@link AbstractEventLoopState} will use to acquire an
event loop from. This also sets the index for the next {@link AbstractEventLoopState} which calls this
method.
core/src/main/java/com/linecorp/armeria/client/DefaultEventLoopScheduler.java