private void writeClientRequestToOrigin(PooledConnection conn, Duration readTimeout) {
        Channel ch = conn.getChannel();
        passport.setOnChannel(ch);

        // set read timeout on origin channel
        ch.attr(ClientTimeoutHandler.ORIGIN_RESPONSE_READ_TIMEOUT).set(readTimeout);

        context.put(CommonContextKeys.ORIGIN_CHANNEL, ch);
        context.set(POOLED_ORIGIN_CONNECTION_KEY, conn);

        preWriteToOrigin(chosenServer.get(), zuulRequest);

        ChannelPipeline pipeline = ch.pipeline();
        originResponseReceiver = getOriginResponseReceiver();
        pipeline.addBefore(
                DefaultOriginChannelInitializer.CONNECTION_POOL_HANDLER,
                OriginResponseReceiver.CHANNEL_HANDLER_NAME,
                originResponseReceiver);

        ch.write(zuulRequest);
        writeBufferedBodyContent(zuulRequest, ch);
        ch.flush();

        // Get ready to read origin's response
        syncClientAndOriginChannels(channelCtx.channel(), ch);
        ch.read();

        originConn = conn;
        channelCtx.read();
    }
Override to track your own request stats.
zuul-core/src/main/java/com/netflix/zuul/filters/endpoint/ProxyEndpoint.java