private Message createMessage(SourceData sourceData) {
        Map<String, String> header = new HashMap<>();
        header.put(OFFSET, sourceData.getOffset());
        header.put(PROXY_KEY_STREAM_ID, inlongStreamId);
        if (extendedHandler != null) {
            extendedHandler.dealWithHeader(header, sourceData.getData());
        }
        Message finalMsg = new DefaultMessage(sourceData.getData(), header);
        // if the message size is greater than max pack size,should drop it.
        if (finalMsg.getBody().length > maxPackSize) {
            LOGGER.warn("message size is {}, greater than max pack size {}, drop it!",
                    finalMsg.getBody().length, maxPackSize);
            return null;
        }
        return finalMsg;
    }
Returns the name of the thread, used to identify different data sources

@return source data list
inlong-agent/agent-plugins/src/main/java/org/apache/inlong/agent/plugin/sources/file/AbstractSource.java