public void initializePutManagerMetrics(final Thread chunkFillerThread) {
    chunkFillerThreadRunning = () -> chunkFillerThread.isAlive() ? 1L : 0L;
    metricRegistry.gauge(MetricRegistry.name(PutManager.class, chunkFillerThread.getName() + "Running"),
        () -> chunkFillerThreadRunning);
  }
Initializes a {@link Gauge} metric for the status of {@code ChunkFillerThread} of a {@link PutManager}, to
indicate if it is running or not.
@param chunkFillerThread The {@code ChunkFillerThread} of which the status is to be monitored.
ambry-router/src/main/java/com/github/ambry/router/NonBlockingRouterMetrics.java