@Override
    public void run() {
      synchronized (SnapshotFileCache.this) {
        try {
          SnapshotFileCache.this.refreshCache();
        } catch (IOException e) {
          LOG.warn("Failed to refresh snapshot hfile cache!", e);
          // clear all the cached entries if we meet an error
          cache = ImmutableSet.of();
          snapshots = ImmutableMap.of();
        }
      }
    }
Simple helper task that just periodically attempts to refresh the cache
hbase-server/src/main/java/org/apache/hadoop/hbase/master/snapshot/SnapshotFileCache.java