ColumnStore Monitor

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.

Required Grants

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'@'%';

Master Selection

The automatic master detection only works with ColumnStore 1.2. 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.

Configuration

Read the Monitor Common document for a list of supported common monitor parameters.

primary

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.

Example

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.