Re: Data Node Won't Start: Internal program error (failed ndbrequire)

[Mauritz Sundell]

If a table have shrunken much in size, its memory usage may still be higher than actual data.

Row data are stored on pages, when rows are deleted it may leave pages partly filled.

The whole page is counted into the memory usage even if partly filled.

The empty unused space in pages will be reused when new rows are inserted.


To verify that both nodes have the same data one can check the row count for each table on each node:

mysql> select fq_name,node_id,SUM(fixed_elem_count) row_count from ndbinfo.memory_per_fragment group by fq_name,node_id;

If there are no writes to the table the row count on both nodes should match.

If there are writes ongoing the numbers can fluctuate depending on the load.

For more information about ndbinfo tables:

https://dev.mysql.com/doc/refman/8.0/en/mysql-cluster-ndbinfo-memory-per-fragment.html

https://dev.mysql.com/doc/refman/8.0/en/mysql-cluster-ndbinfo.html