public int getFlag() {
        return this.flag;
    }
init with indexId topic data attribute flag

@param indexId    index id
@param topic      topic name
@param data       message content
@param attribute  message attribute
@param flag       message flag
inlong-tubemq/tubemq-core/src/main/java/org/apache/inlong/tubemq/corebase/Message.java