Deploy MaxScale 22.08 with MariaDB Monitor and Read/Write Split Router

This page is part of MariaDB's Documentation.

The parent of this page is: MariaDB Deployment

Topics on this page:

Overview
Prerequisites
MaxScale Components
Term Definitions
Installation
Configuration
Start the MaxScale Service
Testing
- Check MaxScale Status
- Test Load Balancing

Overview

This procedure provides instructions for deploying MariaDB MaxScale 22.08 with MariaDB Community Server in a Primary/Replica Topology. If you are using MariaDB Enterprise Server, see "Deploy Primary/Replica Topology".

These instructions detail how to deploy MariaDB MaxScale as a load balancing and high availability solution for MariaDB Replication.

Prerequisites

These instructions assume that the back-end MariaDB Server instances have already been deployed.

See the following resources for how to deploy Primary and Replica servers:

MaxScale Components

These instructions detail the deployment of MaxScale with the following components:

Component	Description
MariaDB Monitor (mariadbmon)	It monitors MariaDB Replication deployments. It supports MariaDB Community Server.
Read/Write Split Router (readwritesplit)	It increases the read-only processing capability of a cluster while maintaining consistency. It splits the query load into read and write queries. It routes read queries to multiple replica servers. It routes write queries to a single primary server. If the primary server changes, then it routes write queries to the new primary server.

Term Definitions

Term	Definition
MaxScale instance	MariaDB MaxScale running by itself on a single host. It interacts with other hosts, such as deployments using MariaDB Replication, Galera Cluster Galera Cluster, and ColumnStore. It serves as the database proxy and load balancer.

Installation

MariaDB Corporation provides package repositories for YUM (RHEL, CentOS), APT (Debian, Ubuntu), and ZYpp (SLES).

Install via YUM (CentOS, RHEL)

Retrieve your Customer Download Token at https://customers.mariadb.com/downloads/token/ and substitute for CUSTOMER_DOWNLOAD_TOKEN in the following directions.

Configure the YUM package repository.

Installable versions of MariaDB MaxScale are 24.02, 23.08, 23.02, 22.08, 6, 2.5, and 2.4. Pass the version you want to install using the --mariadb-maxscale-version flag to the mariadb_es_repo_setup script. The following directions reference 22.08.

To configure YUM package repositories:

$ sudo yum install curl

$ curl -LsSO https://dlm.mariadb.com/enterprise-release-helpers/mariadb_es_repo_setup

$ echo "c12da6a9baa57eab7fa685aa24bf76e6929a8c67f4cd244835520c0181007753  mariadb_es_repo_setup" \
    | sha256sum -c -

$ chmod +x mariadb_es_repo_setup

$ sudo ./mariadb_es_repo_setup --token="CUSTOMER_DOWNLOAD_TOKEN" --apply \
   --mariadb-maxscale-version="22.08"

Install MariaDB MaxScale and package dependencies:
```
$ sudo yum install maxscale
```
Configure MaxScale.

Installation only loads MariaDB MaxScale to the system. MariaDB MaxScale requires configuration before MaxScale is ready for use.

See Configuration.

Install via APT (Debian, Ubuntu)

Retrieve your Customer Download Token at https://customers.mariadb.com/downloads/token/ and substitute for CUSTOMER_DOWNLOAD_TOKEN in the following directions.

Configure the APT package repository.

To configure APT package repositories:

$ sudo apt install curl

$ curl -LsSO https://dlm.mariadb.com/enterprise-release-helpers/mariadb_es_repo_setup

$ echo "c12da6a9baa57eab7fa685aa24bf76e6929a8c67f4cd244835520c0181007753  mariadb_es_repo_setup" \
    | sha256sum -c -

$ chmod +x mariadb_es_repo_setup

$ sudo ./mariadb_es_repo_setup --token="CUSTOMER_DOWNLOAD_TOKEN" --apply \
   --mariadb-maxscale-version="22.08"

$ sudo apt update

Install MariaDB MaxScale and package dependencies:
```
$ sudo apt install maxscale
```
Configure MaxScale.

Installation only loads MariaDB MaxScale to the system. MariaDB MaxScale requires configuration before MaxScale is ready for use.

See Configuration.

Install via ZYpp (SLES)

Retrieve your Customer Download Token at https://customers.mariadb.com/downloads/token/ and substitute for CUSTOMER_DOWNLOAD_TOKEN in the following directions.

Configure the ZYpp package repository.

To configure ZYpp package repositories:

$ sudo zypper install curl

$ curl -LsSO https://dlm.mariadb.com/enterprise-release-helpers/mariadb_es_repo_setup

$ echo "c12da6a9baa57eab7fa685aa24bf76e6929a8c67f4cd244835520c0181007753  mariadb_es_repo_setup" \
    | sha256sum -c -

$ chmod +x mariadb_es_repo_setup

$ sudo ./mariadb_es_repo_setup --token="CUSTOMER_DOWNLOAD_TOKEN" --apply \
   --mariadb-maxscale-version="22.08"

Install MariaDB MaxScale and package dependencies:
```
$ sudo zypper install maxscale
```
Configure MaxScale.

Installation only loads MariaDB MaxScale to the system. MariaDB MaxScale requires configuration before MaxScale is ready for use.

See Configuration.

Configuration

MariaDB MaxScale's parameters can be configured in two ways:

All parameters can be set in a configuration file (such as the /etc/maxscale.cnf file). When the configuration file is updated, the MaxScale instance must be restarted to apply the changes.
If a parameter supports dynamic changes, it can be set on-the-fly using the MaxCtrl utility.

Configure MaxScale's Global Parameters

Determine which global parameters you need to configure.

Useful global parameters for MariaDB MaxScale:

Parameter	Description
local_address	Sets the local IP address or network interface to use when connecting to MariaDB Community Servers.
admin_enabled	Sets whether the MaxScale Instance supports the REST API. Disable to block access.
admin_host	Sets the network interface used by the REST API.
admin_port	Sets the port used by the REST API.
admin_auth	Sets whether the REST API uses HTTP Basic Access authentication. Users can be created with maxctrl.

Set your global parameters in maxscale.cnf.

MariaDB MaxScale global parameters, which apply to the all MaxScale modules, are set in the [maxscale] configuration group:

For example:
```
[maxscale]
admin_auth    = true
```

Configure Servers

Determine which server parameters you need to configure.

Mandatory parameters for Server objects:

Parameter	Description
`type`	Set the module type to `server`.
`address`	Set the IP address for the MariaDB Community Server.
`port`	Set the port the MariaDB Community Server listens on.
`protocol`	Set the protocol to `MariaDBBackend` to connect the Server.

Set your server parameters in maxscale.cnf.

For each Server in your deployment, add a new uniquely-named configuration group to the MaxScale Instance. The name of the configuration group is arbitrary, but it cannot contain any white space. Use whatever terms you find most convenient, but it is most common to use names like serverN or the server's host name.

For example:
```
[server1]
type     = server
address  = 192.0.2.102
port     = 3306
protocol = MariaDBBackend
```

Configure MariaDB Monitor

Determine which parameters for MariaDB Monitor (mariadbmon) you need to configure.

Mandatory parameters for MariaDB Monitor (mariadbmon):

Parameter	Description
`type`	Set the type to `monitor`.
`module`	Set to `mariadbmon` for MariaDB Replication.
`servers`	Set to a comma-separated list of the Server object names.
`user`	Set to the user MariaDB MaxScale uses to connect to the Servers.
`password`	Set to the password MariaDB MaxScale uses to authenticate on the Servers.

Useful parameters for MariaDB Monitor (mariadbmon):

Parameter	Description
`auto_failover`	Enables Automatic Failover for MariaDB Replication deployments, allowing the monitor to respond to a master server failure by reconfiguring a replica server to operate as the new master server.
`auto_rejoin`	Enables Automatic Rejoin for MariaDB Replication deployments, allowing the monitor to reconfigure replica servers that were down during Automatic Failover to use the new master server.

Set your MariaDB Monitor parameters in maxscale.cnf.

Add a new uniquely-named configuration group for the monitor to the MaxScale Instance. The name of the configuration group is arbitrary, but it cannot contain any white space. Use whatever terms you find most convenient, but it is most common to use names like repl-monitor.

For example:
```
[repl-monitor]
type          = monitor
module        = mariadbmon
servers       = server1,server2,server3
user          = maxscale
password      = max_passwd
auto_failover = ON
auto_rejoin   = ON
```

Configure Read/Write Split Router

Determine which parameters for Read/Write Split Router (readwritesplit) you need to configure.

Mandatory parameters for Read/Write Split Router (readwritesplit):

Parameter	Description
`type`	Set the module type as `service`.
`router`	Use to set the type of router you want to use for the service. For the Read/Write Split router, set to `readwritesplit`.
`servers`	Set as a comma-separated list of the Server object names.
`user`	Set the user you want the MaxScale Instance to use when connecting to Servers.
`password`	Set the password you want the MaxScale Instance to use in authentication when connecting to Servers.

Set your Read/Write Split Router parameters in maxscale.cnf.

Add a new uniquely-named configuration group for the router to the MaxScale Instance. The name of the configuration group is arbitrary, but it cannot contain any white space. Use whatever terms you find most convenient, but it is most common to use names like split-router.

For example:
```
[split-router]
type     = service
router   = readwritesplit
servers  = server1,server2,server3
user     = maxscale
password = max_passwd
```

Configure the Router's Listener

Determine which parameters for the listener you need to configure.

Mandatory parameters for the listener:

Parameter	Description
`type`	Set the module type as a `listener`.
`service`	Use this parameter to connect the listener to a configured routing service.
`protocol`	Set this parameter to `MariaDBClient` to handle incoming client connections.
`port`	Set this parameter to specify the port you want the MaxScale Instance to listen on.

Set your listener parameters in maxscale.cnf.

Add a new uniquely-named configuration group for the listener to the MaxScale Instance. The name of the configuration group is arbitrary, but it cannot contain any white space. Use whatever terms you find most convenient, but it is most common to use names like split-router-listener.

For example:
```
[split-router-listener]
type     = listener
service  = split-router
protocol = MariaDBClient
port     = 3306
```

Configure the User Account

On each back-end MariaDB server, create the user account used by the monitor and the router using the CREATE USER statement. Make sure that the user account can connect from the MaxScale instance's IP address:
```
CREATE USER 'maxscale'@'192.0.2.101'
   IDENTIFIED BY 'max_passwd';
```

On each back-end MariaDB server, grant the required privileges to the user account used by the monitor and the router using the GRANT statement.

For the Read/Write Split Router (readwritesplit) , the global SHOW DATABASES privilege and the SELECT privilege on several of the system's privilege tables are required:

GRANT SHOW DATABASES ON *.*
     TO 'maxscale'@'192.0.2.101';
GRANT SELECT ON mysql.columns_priv
     TO 'maxscale'@'192.0.2.101';
GRANT SELECT ON mysql.db
     TO 'maxscale'@'192.0.2.101';
GRANT SELECT ON mysql.procs_priv
     TO 'mxs'@'192.0.2.101';
GRANT SELECT ON mysql.proxies_priv
     TO 'maxscale'@'192.0.2.101';
GRANT SELECT ON mysql.roles_mapping
     TO 'maxscale'@'192.0.2.101';
GRANT SELECT ON mysql.tables_priv
     TO 'maxscale'@'192.0.2.101';
GRANT SELECT ON mysql.user
     TO 'maxscale'@'192.0.2.101';

For MariaDB Monitor (mariadbmon), the required permissions depend on the version of MariaDB Community Server that is being used.

In CS 10.5.8-5 and later, the following privileges are required:

GRANT BINLOG ADMIN,
   READ_ONLY ADMIN,
   RELOAD,
   REPLICA MONITOR,
   REPLICATION MASTER ADMIN,
   REPLICATION REPLICA ADMIN,
   REPLICATION REPLICA,
   SHOW DATABASES
   ON *.*
   TO 'maxscale'@'192.0.2.101';

In CS 10.5.6-4 and before, the following privileges are required:

GRANT BINLOG ADMIN,
   BINLOG MONITOR,
   READ_ONLY ADMIN,
   RELOAD,
   REPLICATION MASTER ADMIN,
   REPLICATION REPLICA ADMIN,
   REPLICATION REPLICA,
   SHOW DATABASES
   ON *.*
   TO 'maxscale'@'192.0.2.101';

In CS 10.4 and before, the following privileges are required:

GRANT SUPER,
   REPLICATION CLIENT,
   RELOAD,
   PROCESS,
   SHOW DATABASES,
   EVENT
   ON *.*
   TO 'maxscale'@'192.0.2.101';

Start the MaxScale Service

MariaDB MaxScale installations include configuration to start, stop, restart, enable/disable on boot, and check the status of the MaxScale Instance using the operating system default process management system.

For distributions that use systemd (most supported OSes), you can manage the MaxScale process using the systemctl command:

Operation	Command
Start	`sudo systemctl start maxscale`
Stop	`sudo systemctl stop maxscale`
Restart	`sudo systemctl restart maxscale`
Enable during startup	`sudo systemctl enable maxscale`
Disable during startup	`sudo systemctl disable maxscale`
Status	`sudo systemctl status maxscale`

Testing

When you have MariaDB MaxScale up and running, you should test it to ensure that it is working and that weren't any issues during startup.

Check MaxScale Status

Check that MaxScale is running properly by using the MaxCtrl utility:

$ sudo maxctrl show maxscale

┌──────────────┬──────────────────────────────────────────────────────────────────────┐
│ Version      │ 22.08.12                                                             │
├──────────────┼──────────────────────────────────────────────────────────────────────┤
│ Commit       │ 61b8bbf7f63c38ca9c408674e66f3627a0b2192e                             │
├──────────────┼──────────────────────────────────────────────────────────────────────┤
│ Started At   │ Fri, 30 Jul 2021 18:05:18 GMT                                        │
├──────────────┼──────────────────────────────────────────────────────────────────────┤
│ Activated At │ Fri, 30 Jul 2021 18:05:18 GMT                                        │
├──────────────┼──────────────────────────────────────────────────────────────────────┤
│ Uptime       │ 109                                                                  │
├──────────────┼──────────────────────────────────────────────────────────────────────┤
│ Parameters   │ {                                                                    │
│              │     "libdir": "/usr/lib/x86_64-linux-gnu/maxscale",                  │
│              │     "datadir": "/var/lib/maxscale",                                  │
│              │     "process_datadir": "/var/lib/maxscale/data3850",                 │
│              │     "cachedir": "/var/cache/maxscale",                               │
│              │     "configdir": "/etc",                                             │
│              │     "config_persistdir": "/var/lib/maxscale/maxscale.cnf.d",         │
│              │     "module_configdir": "/etc/maxscale.modules.d",                   │
│              │     "piddir": "/var/run/maxscale",                                   │
│              │     "logdir": "/var/log/maxscale",                                   │
│              │     "langdir": "/var/lib/maxscale",                                  │
│              │     "execdir": "/usr/bin",                                           │
│              │     "connector_plugindir": "/usr/lib/x86_64-linux-gnu/mysql/plugin", │
│              │     "threads": 1,                                                    │
│              │     "thread_stack_size": 8388608,                                    │
│              │     "writeq_high_water": 0,                                          │
│              │     "writeq_low_water": 0,                                           │
│              │     "auth_connect_timeout": 3,                                       │
│              │     "auth_read_timeout": 1,                                          │
│              │     "auth_write_timeout": 2,                                         │
│              │     "skip_permission_checks": false,                                 │
│              │     "admin_auth": true,                                              │
│              │     "admin_enabled": true,                                           │
│              │     "admin_log_auth_failures": true,                                 │
│              │     "admin_host": "127.0.0.1",                                       │
│              │     "admin_port": 8989,                                              │
│              │     "admin_ssl_key": "",                                             │
│              │     "admin_ssl_cert": "",                                            │
│              │     "admin_ssl_ca_cert": "",                                         │
│              │     "admin_pam_readwrite_service": "",                               │
│              │     "admin_pam_readonly_service": "",                                │
│              │     "passive": false,                                                │
│              │     "query_classifier": "",                                          │
│              │     "query_classifier_cache_size": 155008819,                        │
│              │     "retain_last_statements": 0,                                     │
│              │     "dump_last_statements": "never",                                 │
│              │     "session_trace": 0,                                              │
│              │     "load_persisted_configs": true,                                  │
│              │     "max_auth_errors_until_block": 10                                │
│              │ }                                                                    │
└──────────────┴──────────────────────────────────────────────────────────────────────┘

Test Load Balancing

In a MariaDB Replication deployment, each MariaDB Community Server has the server_id system variable set to a unique value. You can see what server you are connected to by querying this variable:

SELECT @@server_id AS "Server ID";

+-----------+
| Server ID |
+-----------+
|         2 |
+-----------+

We can also use this system variable to test the Read/Write Split Router's load balancing:

Connect to the MaxScale instance using MariaDB Client:

$ mariadb --host=maxscale \
   --port=3306 \
   --user=myuser \
   --password

Create a test table:

CREATE TABLE test.readwrite_test (
   id INT PRIMARY KEY AUTO_INCREMENT,
   write_id INT
);

Insert the value of the the server_id system variable to the table using the INSERT statement:

INSERT INTO test.readwrite_test (write_id) VALUES (@@server_id);
INSERT INTO test.readwrite_test (write_id) VALUES (@@server_id);
INSERT INTO test.readwrite_test (write_id) VALUES (@@server_id);

Read the newly-inserted rows while querying the value of the the server_id system variable again using the SELECT statement:

SELECT readwrite.id AS "Primary Key",
   current.id AS "Current Server ID",
   readwrite.write_id AS "Stored Server ID"
FROM (
   SELECT @@server_id AS id
) AS current
INNER JOIN (
   SELECT id, write_id
   FROM test.readwrite_test
) AS readwrite;

The results will show that the primary server's server_id value was written to the table during the INSERT statement, but the replica server's value was read during the SELECT statement:

+-------------+-------------------+------------------+
| Primary Key | Current Server ID | Stored Server ID |
+-------------+-------------------+------------------+
|           1 |                 2 |                1 |
|           2 |                 2 |                1 |
|           3 |                 2 |                1 |
+-------------+-------------------+------------------+