@Override
  public void channelActive(ChannelHandlerContext ctx) {
    this.ctx = ctx;
    nettyMetrics = new NettyMetrics(METRIC_REGISTRY);
    RestRequestMetricsTracker.setDefaults(METRIC_REGISTRY);
  }
A test handler that forms the pipeline of the {@link EmbeddedChannel} used in tests.
<p/>
Exposes some URI strings through which a predefined flow can be executed and verified.
ambry-rest/src/test/java/com/github/ambry/rest/NettyResponseChannelTest.java