code: private static void initialize(Storage storage, String counterId) {
      LOG.debug("Initializing counter shards for resource {}", counterId);
      for (int startIndex = 0; startIndex < NUM_SHARDS; startIndex += TRANSACTION_GROUP_SIZE) {
        initShardRange(storage, counterId, startIndex,
                       Math.min(NUM_SHARDS, startIndex + TRANSACTION_GROUP_SIZE));
      }
    }
docs: Idempotent initialization, so that we don't reset an existing shard to zero - counterId may
  have already been initialized and incremented by another process.