code: static long getCheckpointTxnCount(Configuration conf) {
      long defaultCount = 700000;
      long bytesPerTxn = 100;
  
      return conf.getLong("fs.checkpoint.txns",
          conf.getLong("fs.checkpoint.size", defaultCount * bytesPerTxn)
              / bytesPerTxn);
    }
docs: Gets the checkpoint transaction count. If transaction count
  is not set, try to infer it from checkpoint size (for older
  configurations)
  
  @return the number of transactions after which a checkpoint
  is triggered.