public BufferedMutatorParams setRequestAttribute(String key, byte[] value) {
    if (requestAttributes.isEmpty()) {
      requestAttributes = new HashMap<>();
    }
    requestAttributes.put(key, value);
    return this;
  }
The maximum number of mutations that this buffered mutator will buffer before flushing them
hbase-client/src/main/java/org/apache/hadoop/hbase/client/BufferedMutatorParams.java