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 Columnstore Monitor in MaxScale 2.5 supports Columnstore 1.0, 1.2 and 1.5, and the master selection is done differently for each version.

• If the version is 1.0, the master server must be specified using the primary parameter.
• If the version is 1.2, the master server is selected automatically using the Columnstore function mcsSystemPrimary().
• If the version is 1.5, the master server is selected automatically by querying the Columnstore daemon running on each node.

Configuration

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

version

With this mandatory parameter the used Columnstore version is specified. The allowed values are 1.0, 1.2 and 1.5.

primary

Required and only allowed when the value of version is 1.0.

The primary parameter controls which server is chosen as the master server.

If the server pointed to by this parameter is available and is ready to process queries, it receives the Master status.

admin_port

Allowed only when the value of version is 1.5.

This optional parameter specifies the port of the Columnstore administrative daemon. The default value is 8630. Note that the daemons of all nodes must be listening on the same port.

admin_base_path

Allowed only when the value of version is 1.5.

This optional parameter specifies the base path of the Columnstore administrative daemon. The default value is /cmapi/0.3.0.

api_key

Allowed only when the value of version is 1.5.

This optional parameter specifies the API key to be used in the communication with the Columnstore administrative daemon. If no key is specified, then a key will be generated and stored to the file api_key.txt in the directory with the same name as the monitor in data directory of MaxScale. Typically that will be /var/lib/maxscale/<monitor-section>/api_key.txt.

Note that Columnstore will store the first key provided and thereafter require it, so changing the key requires the resetting of the key on the Columnstore nodes as well.

local_address

Allowed only when the value of version is 1.5.

With this parameter it is specified what IP MaxScale should tell the Columnstore nodes it resides at. Either it or local_address at the global level in the MaxScale configuration file must be specified. If both have been specified, then the one specified for the monitor overrides.

Commands

The Columnstore monitor provides module commands using which the Columnstore cluster can be managed. The commands can be invoked using the REST-API with a client such as curl or using maxctrl.

All commands require the monitor instance name as the first parameters. Additional parameters must be provided depending on the command.

Note that as maxctrl itself has a timeout of 10 seconds, if a timeout larger than that is provided to any command, the timeout of maxctrl must also be increased. For instance:

maxctrl --timeout 30s call command csmon shutdown CsMonitor 20s

Here a 30 second timeout is specified for maxctrl to ensure that it does not expire before the timeout of 20s provided for the shutdown command possibly does.

The output is always a JSON object.

In the following, assume a configuration like this:

[CsNode1]
type=server
...

[CsNode2]
type=server
...

[CsNode3]
type=server
...

[CsMonitor]
type=monitor
module=csmon
servers=CsNode1,CsNode2,CsNode3
...

Start

call command csmon start <monitor-name> <timeout>

Starts the Columnstore cluster.

Example

call command csmon start CsMonitor 20s

Shutdown

call command csmon shutdown <monitor-name> <timeout>

Shuts down the Columnstore cluster.

Example

call command csmon shutdown CsMonitor 20s

Status

call command csmon status <monitor-name> [<server>]

Returns the status of all servers in the cluster or of a specific one.

Example

call command csmon status CsMonitor CsNode1

Set Mode

call command csmon mode-set <monitor-name> (readonly|readwrite) <timeout>

Sets the mode of the cluster.

Example

call command csmon mode-set CsMonitor readonly 20s

Get Config

call command csmon config-get <monitor-name> [<server-name>]

Returns the configs of all servers in the cluster or of a specific one.

Example

call command csmon config-get CsMonitor CsNode2

Example

The following is an example of a csmon configuration.

[CSMonitor]
type=monitor
module=csmon
version=1.5
servers=CsNode1,CsNode2,CsNode3
user=myuser
passwd=mypwd
monitor_interval=5000
api_key=somekey1234