* does).
   *
   * <p>Entries with keys that have been garbage collected may be counted in {@link Cache#size}, but
   * will never be visible to read or write operations; such entries are cleaned up as part of the
   * routine maintenance described in the class javadoc.
   *
   * @return this {@code CacheBuilder} instance (for chaining)
   * @throws IllegalStateException if the key strength was already set
   */

      V value = entry.getValue();
      if (value == null) {
        tryDrainReferenceQueues();
        return null;
      }

      return value;
    }

    /**
     * Performs routine cleanup following a read. Normally cleanup happens during writes, or from
     * the cleanupExecutor. If cleanup is not observed after a sufficient number of reads, try
     * cleaning up from the read thread.
     */

// using a delete-marker and MetaSys entries. It's used to track tiered content of a
// deleted/overwritten version. This version is visible _only_to the scanner routine, for subsequent deletion.
// This kind of tracking is necessary since a version's tiered content is deleted asynchronously.

// Backend directory tree structure:
// disk1/
// └── bucket
//     └── object

	sys.iamRefreshInterval = iamRefreshInterval
	// Initialize IAM store
	sys.initStore(objAPI, etcdClient)
	sys.Unlock()

	retryCtx, cancel := context.WithCancel(ctx)

	// Indicate to our routine to exit cleanly upon return.
	defer cancel()

	r := rand.New(rand.NewSource(time.Now().UnixNano()))

	// Migrate storage format if needed.
	for {
		// Migrate IAM configuration, if necessary.

	}

	pr, pw := xioutil.WaitPipe()
	go func() {
		pw.CloseWithError(er.getObjectWithFileInfo(ctx, bucket, object, off, length, pw, fi, metaArr, onlineDisks))
	}()

	// Cleanup function to cause the go routine above to exit, in
	// case of incomplete read.
	pipeCloser := func() {
		pr.CloseWithError(nil)
	}

	if !unlockOnDefer {
		return fn(pr, h, pipeCloser, nsUnlocker)
	}

		globalLeaderLock = newSharedLock(GlobalContext, z, "leader.lock")
	})

	// Enable background operations on
	//
	// - Disk auto healing
	// - MRF (most recently failed) healing
	// - Background expiration routine for lifecycle policies
	bootstrapTrace("initAutoHeal", func() {
		initAutoHeal(GlobalContext, z)
	})

	bootstrapTrace("initHealMRF", func() {
		go globalMRFState.healRoutine(z)
	})

          "datasource": {
            "type": "prometheus",
            "uid": "${DS_PROMETHEUS}"
          },
          "editorMode": "code",
          "exemplar": true,
          "expr": "minio_node_go_routine_total{job=~\"$scrape_jobs\"}",
          "format": "time_series",
          "hide": false,
          "instant": false,
          "interval": "",
          "intervalFactor": 1,
          "legendFormat": "{{server}}",