@Override
  public byte[] getRequestAttribute(String key) {
    if (this.requestAttributes == null) {
      for (HBaseProtos.NameBytesPair nameBytesPair : header.getAttributeList()) {
        if (nameBytesPair.getName().equals(key)) {
          return nameBytesPair.getValue().toByteArray();
        }
      }
      return null;
    }
    return this.requestAttributes.get(key);
  }
Call is done. Execution happened and we returned results to client. It is now safe to cleanup.
hbase-server/src/main/java/org/apache/hadoop/hbase/ipc/ServerCall.java