private HttpRequest buildOriginHttpRequest(HttpRequestMessage zuulRequest) {
        String method = zuulRequest.getMethod().toUpperCase(Locale.ROOT);
        String uri = pathAndQueryString(zuulRequest);

        customRequestProcessing(zuulRequest);

        DefaultHttpRequest nettyReq =
                new DefaultHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.valueOf(method), uri, false);
        // Copy headers across.
        for (Header h : zuulRequest.getHeaders().entries()) {
            nettyReq.headers().add(h.getKey(), h.getValue());
        }

        return nettyReq;
    }
Override to add custom post complete functionality

@param ctx - channel handler context
@param evt - netty event
@throws Exception
zuul-core/src/main/java/com/netflix/zuul/netty/server/OriginResponseReceiver.java