@Override
    public void channelActive(ChannelHandlerContext ctx) {
      perfClientMetrics.channelCreationRate.mark();
      logger.trace("Channel {} active", ctx.channel());
      sendRequest(ctx);
    }
Custom handler that sends out the request and receives and processes the response.
TODO support GET-after-POST and DELETE-after-POST operations for race condition testing.
ambry-tools/src/main/java/com/github/ambry/tools/perf/rest/NettyPerfClient.java