@Override
        public void handleOutbound(HandlerContext ctx, OutboundMessageEvent<?> event) throws Exception {
            if (event != null) {
                DefaultPipelineFuture.received(event.getInvokeId(), event.getMessage());
            }
        }
Most of the code references the pipeline design of
<a href="https://github.com/netty/netty">Netty</a>.

@author jiachun.fjc
jraft-rheakv/rheakv-core/src/main/java/com/alipay/sofa/jraft/rhea/util/pipeline/DefaultPipeline.java