void registerConnectionsStatsHandler(final AtomicLong openConnectionsCount) {
    Gauge<Long> openConnections = openConnectionsCount::get;
    metricRegistry.register(MetricRegistry.name(ConnectionStatsHandler.class, "OpenConnections"), openConnections);
  }
Registers the {@link ConnectionStatsHandler} to track open connections
@param openConnectionsCount open connections count to be tracked
ambry-rest/src/main/java/com/github/ambry/rest/NettyMetrics.java