The ColumnStore monitor, csmon, is a monitor module for MariaDB ColumnStore
servers. It supports multiple UM nodes and can detect the correct server for
DML/DDL statements which will be labeled as the master. Other UM nodes will be
used for reads.
The credentials defined with the user and password parameters must have all
grants on the infinidb_vtable database.
For example, to create a user for this monitor with the required grants execute the following SQL.
CREATE USER 'maxuser'@'%' IDENTIFIED BY 'maxpwd';
GRANT ALL ON infinidb_vtable.* TO 'maxuser'@'%';
The automatic master detection only works with ColumnStore 1.1.7 (planned version at the time of writing). Older versions of ColumnStore do not implement the required functionality to automatically detect which of the servers is the primary UM.
With older versions the primary parameter must be defined to tell the monitor
which of the servers is the primary UM node. This guarantees that DDL statements
are only executed on the primary UM.
Read the Monitor Common document for a list of supported common monitor parameters.
The primary parameter controls which server is chosen as the master
server. This is an optional parameter.
If the server pointed to by this parameter is available and is ready to process
queries, it receives the Master status. If the parameter is not defined and
the ColumnStore server does not support the mcsSystemPrimary function, no
master server is chosen.
Note that this parameter is only used when the server does not implement the required functionality. Otherwise the parameter is ignored as the information from ColumnStore itself is more reliable.
The following is an example of a csmon configuration.
[CS-Monitor]
type=monitor
module=csmon
servers=um1,um2,um3
user=myuser
passwd=mypwd
monitor_interval=5000
primary=um1
It defines a set of three UMs and defines the UM um1 as the primary UM.