Rotation of mdsd logs is needed

The log file mdsd.warn has been more than 15GB, and it results in out of space. The log file is filled up with:

2019-01-07T08:26:17.0908640Z: Event source tag-reader is slow; dropping tag 1546849532:8522944.564241800
2019-01-09T05:56:31.9997230Z: Event source tag-reader is slow; dropping tag 1547013342:116.478485700

My questions:
1. What does the message "Event source tag-reader is slow; dropping tag ***" mean? I noticed it usually appears while starting mdsd;
2. When will the log rotation logic be added to the extension? It looks like the extension v3.0 does not have log rotation feature either.

Thanks.