@Override
      public void operationComplete(ChannelFuture future) throws Exception {
        long responseFlushTime = System.currentTimeMillis() - sendStartTime;
        http2ServerMetrics.responseFlushTime.update(responseFlushTime);
        if (metrics != null) {
          metrics.updateSendTime(responseFlushTime);
        }
      }
Send a response back via netty outbound handlers
ambry-network/src/main/java/com/github/ambry/network/NettyServerRequestResponseChannel.java