@Override
  public boolean isOpen() {
    return !responseCompleteCalled.get() && ctx.channel().isActive();
  }
Create an instance of NettyResponseChannel that will use {@code ctx} to return responses.
@param ctx the {@link ChannelHandlerContext} to use.
@param nettyMetrics the {@link NettyMetrics} instance to use.
@param performanceConfig the configuration object to use for performance evaluation.
@param nettyConfig the configuration object to use for netty related config.
ambry-rest/src/main/java/com/github/ambry/rest/NettyResponseChannel.java