@Override
  public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
    inFlightRequests.incrementAndGet();
    super.write(ctx, msg, promise);
  }
A handler to track requests stats. For now, it only tracks in-flight request count.
ambry-network/src/main/java/com/github/ambry/network/http2/RequestsStatsHandler.java