Deploy MaxScale 2.5 on RHEL 8 with Galera Monitor and Read Connection Router

Prerequisites
MariaDB Platform Components
MaxScale Components
Term Definitions
Installation
- Install via YUM (RHEL/CentOS)
Configuration
Starting the MaxScale Instance
Testing
- Checking MaxScale Status

These instructions detail the deployment of MariaDB MaxScale 2.5 on Red Hat Enterprise Linux 8 in a MaxScale Instance with Galera Monitor and Read Connection Router.

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

Prerequisites

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

See the following resources for how to deploy Galera Cluster nodes:

MariaDB Platform Components

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

Component	Description
MariaDB MaxScale 2.5	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
Galera Monitor (galeramon)	It monitors Galera Cluster deployments. It supports MariaDB Enterprise Cluster. It supports MariaDB Galera Cluster.
Read Connection Router (readconnroute)	It provides simple and lightweight load balancing of connections across a set of servers. It works best for use cases where each client connection needs a consistent connection to a single back-end server, and where queries can be executed on any back-end server. It can be configured to route connections to any running server, any primary server, or any replica server. If connections are routed to non-primary servers, the application should only use read-only queries to maintain consistency of data.

Component

Description

Galera Monitor (galeramon)

It monitors Galera Cluster deployments.
It supports MariaDB Enterprise Cluster.
It supports MariaDB Galera Cluster.

Read Connection Router (readconnroute)

It provides simple and lightweight load balancing of connections across a set of servers.
It works best for use cases where each client connection needs a consistent connection to a single back-end server, and where queries can be executed on any back-end server.
It can be configured to route connections to any running server, any primary server, or any replica server.
If connections are routed to non-primary servers, the application should only use read-only queries to maintain consistency of data.

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, and ColumnStore. It serves as the database proxy and load balancer.

Installation

MariaDB Corporation provides a YUM package repository for Red Hat Enterprise Linux 8.

Install via YUM (RHEL/CentOS)

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.

To configure YUM package repositories:

$ sudo yum install wget

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

$ echo "c78db828709d94876406a0ea346f13fbc38e73996795903f40e3c21385857dd4  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="2.5"

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.

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

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.

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

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.

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 Galera Monitor

Determine which parameters for Galera Monitor (galeramon) you need to configure.

Mandatory parameters for Galera Monitor (galeramon):

Parameter	Description
`type`	Set the type to `monitor`.
`module`	Set to `galeramon` for MariaDB Enterprise Cluster.
`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 Galera Monitor (galeramon):

Parameter	Description
`disable_master_failback`	If a node marked as master inside MaxScale happens to fail and the master status is assigned to another node MaxScale will normally return the master status to the original node after it comes back up. With this option enabled, if the master status is assigned to a new node it will not be reassigned to the original node for as long as the new master node is running.
`available_when_donor`	This option allows Galera nodes to be used normally when they are donors in an SST operation when the SST method is non-blocking.

Set your Galera 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 cluster-monitor.

For example:
```
[cluster-monitor]
type           = monitor
module         = galeramon
servers        = server1,server2,server3
user           = maxscale
password       = max_passwd
```

Configuring Read Connection Router

Determine which parameters for Read Connection Router (readconnroute) you need to configure.

Mandatory parameters for Read Connection Router (readconnroute):

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 Connection Router, set to `readconnroute`.
`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.
`router_options`	Set to a comma separated list of valid server roles. These roles are used as the valid types of servers the router will form connections to when new sessions are created. Choose from `running`, `synced`, `master`, and `slave`.

Set your Read Connection 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 connection-router.

For example:
```
[connection-router]
type           = service
router         = readconnroute
servers        = server1,server2,server3
user           = maxscale
password       = max_passwd
router_options = synced
```

Configuring 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 connection-router-listener.

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

Configuring 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'@'192.0.2.1'
   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 Connection Router (readconnroute), 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 Galera Monitor (galeramon), the required permissions depend on the version of MariaDB Enterprise Server that is being used.

In ES10.5.8-5 and later, the following privileges are required:

GRANT BINLOG MONITOR,
   REPLICA MONITOR
   ON *.*
   TO 'maxscale'@'192.0.2.1';

In ES10.5.6-4 and before, the following privileges are required:

GRANT BINLOG MONITOR,
   REPLICATION SLAVE ADMIN
   ON *.*
   TO 'maxscale'@'192.0.2.1';

In ES10.4 and before, the following privileges are required:

GRANT REPLICATION CLIENT
   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.

Red Hat Enterprise Linux 8 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

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

$ sudo maxctrl show maxscale

┌──────────────┬──────────────────────────────────────────────────────────────────────┐
│ Version      │ 2.5.8                                                              │
├──────────────┼──────────────────────────────────────────────────────────────────────┤
│ 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                                │
│              │ }                                                                    │
└──────────────┴──────────────────────────────────────────────────────────────────────┘