void initializeCompactionThreadsTracker(final StorageManager storageManager, final int diskCount) {
    Gauge<Integer> compactionThreadsCountGauge = storageManager::getCompactionThreadCount;
    registry.register(MetricRegistry.name(StorageManager.class, "CompactionThreadsAlive"), compactionThreadsCountGauge);
    Gauge<Integer> compactionHealthGauge = () -> storageManager.getCompactionThreadCount() == diskCount ? 1 : 0;
    registry.register(MetricRegistry.name(StorageManager.class, "CompactionHealth"), compactionHealthGauge);
  }
Initializes gauges that track the compaction thread counts.
@param storageManager the {@link StorageManager} instance to use to obtain values.
@param diskCount the number of disks that the {@link StorageManager} handles.
ambry-store/src/main/java/com/github/ambry/store/StorageManagerMetrics.java