@Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        if (msg instanceof HttpRequest) {
            final Boolean currentlyInUse = ctx.channel().attr(IN_USE).get();
            if (currentlyInUse != null && currentlyInUse == true) {
                // Pipelining not supported so just ignore the request if another request already being handled.
                ReferenceCountUtil.release(msg);
                return;
            }

            ctx.channel().attr(StateKey.REQUEST_ID).set(UUID.randomUUID());
            ctx.channel().attr(IN_USE).set(true);
        }

        ctx.fireChannelRead(msg);
    }
The key for whether a {@link io.netty.handler.codec.http.HttpResponse} has been sent for the current response.
gremlin-server/src/main/java/org/apache/tinkerpop/gremlin/server/handler/HttpRequestIdHandler.java