void registerNettyPendingTasksGauge(EventLoopGroup eventLoopGroup, String groupName) {
    Gauge<Long> pendingTasksGetter = () -> Utils.getNumberOfPendingTasks(eventLoopGroup);
    metricRegistry.register(MetricRegistry.name(NettyServer.class, "Netty" + groupName + "PendingTasks"),
        pendingTasksGetter);
  }
Registers pendingTasks of NettyServer worker's EventLoopGroup to track
@param eventLoopGroup the {@link EventLoopGroup} tracked
@param groupName the eventLoopGroup's name: Worker or Boss
ambry-rest/src/main/java/com/github/ambry/rest/NettyMetrics.java