NDB Cluster Internals  /  NDB Kernel Blocks  /  The DBINFO Block

4.6 The DBINFO Block

The DBINFO block provides support for the ndbinfo information database used to obtain information about data node internals.

An API node communicates with this block to retrieve ndbinfo data using DBINFO_SCANREQ and DBINFO_SCANCONF signals. The API node communicates with DBINFO on the master data node, which communicates with DBINFO on the remaining data nodes. The DBINFO block on each data node fetches information from the other kernel blocks on that node, including DBACC, DBTUP, BACKUP, DBTC, SUMA, DBUTIL, TRIX, DBTUX, DBDICT, CMVMI, DBLQH, LGMAN, PGMAN, DBSPJ, THRMAN, TRPMAN, and QMGR. The local DBINFO then sends the information back to DBINFO on the master node, which in turn passes it back to the API node.

This block is implemented in the file storage/ndb/src/kernel/blocks/dbinfo/Dbinfo.hpp as the Dbinfo class. The file Dbinfo.cpp in the same directory defines the methods of this class (mostly signal handlers). Also in the dbinfo directory is a text file DbinfoScan.txt which provides information about DBINFO messaging.