@RestrictedApi(explanation = "Should only be called in tests", link = "",
      allowedOnPath = ".*/src/test/.*")
  synchronized void setLastCachedAt(long timestamp) {
    lastCachedAt = timestamp;
  }
For tests only, sets lastCachedAt so we can force a refresh
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/InputStreamBlockDistribution.java