@Override
            public Optional<T> load(String key) {
              try {
                return Optional.of(supplier.get());
              } catch (Exception e) {
                LOG.warn("Failed to refresh cache {}", name, e);
                return Optional.empty();
              }
            }
This will call {@link #updateMachineQuotaFactors(int)}, and then update the table machine
factors as well. This relies on a more expensive query for ClusterMetrics.
hbase-server/src/main/java/org/apache/hadoop/hbase/quotas/QuotaCache.java