Deploy MaxScale 2.4 on Ubuntu 20.04 LTS with MariaDB Monitor and Read/Write Split Router

These instructions detail the deployment of MariaDB MaxScale 2.4 on Ubuntu 20.04 LTS in a MaxScale Instance with MariaDB Monitor and Read/Write Split Router.

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:

MariaDB Platform Components

These instructions detail the deployment of the following MariaDB Platform components:

Component

Description

MariaDB MaxScale 2.4

  • MariaDB MaxScale is an advanced database proxy, firewall, and query router.

MaxScale Components

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

Component

Description

MariaDB Monitor (mariadbmon)

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

Installation

MariaDB Corporation provides a APT package repository for Ubuntu 20.04 LTS.

Install via APT (Debian/Ubuntu)

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

  2. Configure the APT package repository.

    To configure APT package repositories:

    $ sudo apt install wget
    
    $ wget https://dlm.mariadb.com/enterprise-release-helpers/mariadb_es_repo_setup
    
    $ echo "eeebe9e08dffb8a4e820cc0f673afe437621060129169ea3db0790eb649dbe9b  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="2.4"
    
    $ sudo apt update
    
  3. Install MariaDB MaxScale and package dependencies:

    $ sudo apt install maxscale
    
  4. Configure MaxScale.

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

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.

Configuring MaxScale's Global Parameters

  1. 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 Enterprise 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 wih maxctrl.

  2. Set your global parameters in maxscale.cnf.

    MariaDB MaxScale's global parameters, which apply to the whole instance, are set in the [maxscale] configuration group:

    For example:

    [maxscale]
    admin_auth    = true
    

Configuring Servers

  1. 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 Enterprise Server.

    port

    Set the port the MariaDB Enterprise Server listens on.

    protocol

    Set the protocol to MariaDBBackend to connect the Server.

  2. 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  = 192.0.2.2
    port     = 3306
    protocol = MariaDBBackend
    

Configuring MariaDB Monitor

  1. 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.

  2. 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
    

Configuring Read/Write Split Router

  1. 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 conecting to Servers.

  2. 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
    

Configuring the Router's Listener

  1. 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.

  2. 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
    

Configuring the User Account

  1. 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@192.0.2.1
       IDENTIFIED BY 'max_passwd';
    
  2. 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@192.0.2.1;
    GRANT SELECT ON mysql.columns_priv
         TO maxscale@192.0.2.1;
    GRANT SELECT ON mysql.db
         TO maxscale@192.0.2.1;
    GRANT SELECT ON mysql.proxies_priv
         TO maxscale@192.0.2.1;
    GRANT SELECT ON mysql.roles_mapping
         TO maxscale@192.0.2.1;
    GRANT SELECT ON mysql.tables_priv
         TO maxscale@192.0.2.1;
    GRANT SELECT ON mysql.user
         TO maxscale@192.0.2.1;
    

    For MariaDB Monitor (mariadbmon), the global REPLICATION CLIENT privilege is sufficient for the monitor's basic functionality. The global SUPER, RELOAD, PROCESS, SHOW DATABASES, and EVENT privileges are also required for the monitor's automatic failover and automatic rejoin functionality:

    GRANT SUPER, REPLICATION CLIENT,
         RELOAD, PROCESS, SHOW DATABASES,
         EVENT ON *.*
         TO maxscale@192.0.2.1;
    

Starting the MaxScale Instance

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.

Ubuntu 20.04 LTS uses systemd. 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.

Checking MaxScale Status

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

    $ sudo maxctrl show maxscale
    
    ┌──────────────┬──────────────────────────────────────────────────────────────────────┐
    │ Version      │ 2.4.10                                                              │
    ├──────────────┼──────────────────────────────────────────────────────────────────────┤
    │ Commit       │ 61b8bbf7f63c38ca9c408674e66f3627a0b2192e                             │
    ├──────────────┼──────────────────────────────────────────────────────────────────────┤
    │ Started At   │ Fri, 03 Jan 2020 18:05:18 GMT                                        │
    ├──────────────┼──────────────────────────────────────────────────────────────────────┤
    │ Activated At │ Fri, 03 Jan 2020 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                                │
    │              │ }                                                                    │
    └──────────────┴──────────────────────────────────────────────────────────────────────┘
    

Testing Load Balancing

In a MariaDB Replication deployment, each MariaDB Enterprise 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:

  1. Connect to the MaxScale instance using MariaDB Client:

    $ mariadb --host=maxscale \
       --port=3306 \
       --user=myuser \
       --password
    
  2. Create a test table:

    CREATE TABLE test.readwrite_test (
       id INT PRIMARY KEY AUTO_INCREMENT,
       write_id INT
    );
    
  3. 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);
    
  4. 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 |
    +-------------+-------------------+------------------+